Electronics Project Circuts

Build very low cost FM transmitter, use your TV antenna and transmit upto 4km range!!

<div dir="ltr" style="text-align: left;" trbidi="on">
<span style="color: #38761d;"><u><b><span style="font-size: large;">Here is the specification of the transmitter: </span></b></u></span><br />
<ol style="text-align: left;">
<li>No. of stage: 4</li>
<li>Frequency of operation: About 100MHz</li>
<li>Antenna type: Folded 300 ohms dipole.</li>
<li>Range obtained in free space: Up to 4km with dipole antenna 30 feet above ground level. More   range with yagi antenna.</li>
</ol>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAAk9jblNKzqXrlytMJ_3QR7CxCoyv9nCyornpBAQSCNsVxQM-mq9Aw17EppItb5c8ws0Uykjk8hXSiEb9k-VnNSHxHiAQtZ_0Pu1qayegOz9vTwrS92JkN0jMSbYusekAKJTra3snAq8/s1600/2kmtx_ckt.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAAk9jblNKzqXrlytMJ_3QR7CxCoyv9nCyornpBAQSCNsVxQM-mq9Aw17EppItb5c8ws0Uykjk8hXSiEb9k-VnNSHxHiAQtZ_0Pu1qayegOz9vTwrS92JkN0jMSbYusekAKJTra3snAq8/s1600/2kmtx_ckt.gif" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><b><span style="font-size: small;">Fig: Circuit diagram of the Transmitter</span></b></td></tr>
</tbody></table>
<h3 style="text-align: left;">
Brief Description:-</h3>
<div style="text-align: justify;">
The transmitter is built on a Printed Circuit Board. This board uses track inductor for L1, L2 and part of L3. The section built around Q1 is the oscillator section. Oscillation frequency is determined by L1, C4 & C5 which forms the tank. Actually C5 is the feedback capacitor. This is required to sustain oscillation. This also influence the operation of tank formed by L1 & C4. Modulation is directly applied to the base of Q1 via C2. A microphone is connected here to serve this purpose. You can alternately feed direct audio here after disconnecting the microphone biasing resistor R1. Q2, Q3 & Q4 gradually raises the output power up to the desired level.</div>
<div style="text-align: justify;">
As most of the inductors are PCB etched, there is practically very little frequency drift provided you use a highly regulated and ripple free power supply.</div>
<div style="text-align: justify;">
RF output from the transmitter is taken from the junction of C11 & C12. This is unbalanced output of around 75 ohms impedance. But a folded dipole is a balanced type antenna of around 300 ohms impedance. So we need to use a 'BALanced to UNbalanced transformer' or 'BALUN'. A 1:4 type BALUN is employed here for this purpose. Antenna connection is taken from this BALUN via a 300 ohms flat parallel feeder cable commonly used in television to receive terrestrial broadcast. No coaxia is used to feed antenna. This saves cost. Also a parallel feeder cable provides much less signal loss compared to a coaxial.</div>
<div style="text-align: center;">
<b><span style="color: #bf9000;"><span style="background-color: #0b5394;"> <span style="color: #f1c232;">Click 'Read More" to see details with pictures</span></span></span></b></div>
<h3 style="text-align: left;">
Design of BALUN</h3>
<div style="text-align: justify;">
The BALUN is made using a two-hole binocular ferrite bead as shown above. You need to use parallel insulated twin wire to construct this. This wire is commonly used to wind TV BALUN transformer. If you want to get rid of this, then buy a ready-made TV BALUN that is generally used at the back of your television set for interfacing with feeder wire.</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgP4WkMjLjVq4NuvNqPCCwULRHr5Onc_0DcN36gjVXFR9TKhWs82Vtj3Z1UydcEG7euu_R8a6XR6JikfJm7VQ1T1cAPpBimEPE_pE2vNYNuRPbmLqtubgxR8O-WtuOgJ5A0PuY0FMR9i34/s1600/Bal_cir.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgP4WkMjLjVq4NuvNqPCCwULRHr5Onc_0DcN36gjVXFR9TKhWs82Vtj3Z1UydcEG7euu_R8a6XR6JikfJm7VQ1T1cAPpBimEPE_pE2vNYNuRPbmLqtubgxR8O-WtuOgJ5A0PuY0FMR9i34/s1600/Bal_cir.gif" /></a></div>
<div style="text-align: justify;">
If you prefer to build this yourself, the circuit diagram is given above. You need to carefully construct it keeping in mind about the 'sense' & 'direction' of turns. See there are four coils. Two coils in the upper section, which are red and blue, required to be wound on left side of the BALUN and the remaining two (blue & red) in the lower half to be wound on right side. Connection marked 'A' and 'B' at the left side of the circuit is reqired to be connected to the PCB at the shown point. As dipole antenna is balanced type, so you need not to worry about its connection.</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAekBDFn22xDWW-vvMzlZab3TpPd5VCNLrkI5P_3-28UnokwF3NO7TMUBac7iLtw4mN_FPWD5xUcyaf4aOIVOtFhtGc3EXo9oPjY3P8dU5s0Z8-5ntYHksGyOZX4zDF9PhslG6dqRmsI8/s1600/balun.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="154" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAekBDFn22xDWW-vvMzlZab3TpPd5VCNLrkI5P_3-28UnokwF3NO7TMUBac7iLtw4mN_FPWD5xUcyaf4aOIVOtFhtGc3EXo9oPjY3P8dU5s0Z8-5ntYHksGyOZX4zDF9PhslG6dqRmsI8/s320/balun.gif" width="320" /></a></div>
<h3 style="text-align: left;">
PCB design details</h3>
The transmitter is built on a single sided PCB. As mentioned earlier, this PCB has a number of etched inductors. For this reason, you need to very carefully construct the PCB as mentioned below.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJ9A6E8IDWaHz9ZdmZjnEGNJhONi7bvT6sxKjJEYj10dPm40V9wBmD1IQMTbBN42hXCPRNlZ3ZV5k26Hr0cMxR0J9R9jjV93_HBkTDPUA-aQ-Iza2K8_bBWno2bhvyz-MHxoCwe3Pq0a0/s1600/2kmtx_pcb.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJ9A6E8IDWaHz9ZdmZjnEGNJhONi7bvT6sxKjJEYj10dPm40V9wBmD1IQMTbBN42hXCPRNlZ3ZV5k26Hr0cMxR0J9R9jjV93_HBkTDPUA-aQ-Iza2K8_bBWno2bhvyz-MHxoCwe3Pq0a0/s1600/2kmtx_pcb.gif" /></a></div>
<div style="text-align: justify;">
The above drawing is the copper side and below shown is the component mounting plan.</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-DWmsIe44PX6KXH21aO_a1Ld4h9Qe9txBkABXQ_UAr6TYCiVpLzTmE7QGdxcOMf3X1QWISyzInEZdm_9GBxaOn8CAME2Fvs5ygvDsoV9R7s91f8upRxpwtQ5F4feX2OjdjMHsWPSn6Yg/s1600/2kmtx_lgd.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-DWmsIe44PX6KXH21aO_a1Ld4h9Qe9txBkABXQ_UAr6TYCiVpLzTmE7QGdxcOMf3X1QWISyzInEZdm_9GBxaOn8CAME2Fvs5ygvDsoV9R7s91f8upRxpwtQ5F4feX2OjdjMHsWPSn6Yg/s1600/2kmtx_lgd.gif" /></a></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
In the copper side view, you can see that there are three track etched inductors that resembles 'RCL' Every corner and track width/length are calculated and then they are drawn so that each 'RCL' section becomes an inductor of required value. Never play with this; otherwise, optimum result could not be achieved.</div>
<div style="text-align: justify;">
You need to use a laser printer or a high quality printer to get a printout of the drawings. First, save the picture to disk. Now try to print it from such a software which permits you to control print size. 'Paint Shop Pro' is such a software. Of course you can use any other software. Print the drawing so that copper side drawing is exactly 59mm X 59mm. Few trial will give you the perfect print. Now construct the PCB using 'Photo-etching' method so that all the tracks becomes exactly same as you are now seeing. Now drill the PCB carefully. The PCB is now ready to populate.</div>
<div style="text-align: justify;">
Start population according to the component mounting plan. You can also get a true size copy of this plan printed and glued to the PCB. This will help you work fast.Part of L3 is required to be constructed. This is described in parts list.</div>
<div style="text-align: justify;">
Please note that in the picture of the transmitter kit, capacitor C1 & C10 are not mounted by mistake and the kit is filmed. Please add these two capacitors. Try to keep all component leads as short as possible.</div>
<div style="text-align: justify;">
Now you need to design the dipole antenna to use with the kit.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
N.B: Believe it or not, a 2N2369 from Philips, used in the final power amplifier section, can give this much of range. </div>
<h3 style="text-align: left;">
Detailed Parts List:-</h3>
RESISTORS<br />
R1 - 22K<br />
R2 - 100K<br />
R3, R7, R9 - 1K<br />
R4, R8 - 100E<br />
R5 - 390E<br />
R6 - 330E<br />
R10 - 15E<br />
R11 - 10K<br />
CAPACITORS<br />
C1, C3, C10 - 1n<br />
C2 - 100n<br />
C4,C8,C9 - 47pF<br />
C5, C11 - 10pF<br />
C6 - 100uF/25V Electrolytic<br />
C7 - 100pF<br />
C12 - 3pF<br />
TRANSISTORS<br />
Q1, Q2, Q3 - BC548<br />
Q4 - PN2369 (Plastic casing) or 2N2369 (Metal casing)<br />
MISC.<br />
L3 - 7 turns, 22SWG wire, 3mm ID, Close wound, Air core.<br />
Two hole binocular BALUN core, BALUN wire, 300 ohms TV feeder wire,<br />
JP1 to JP5 - All jumper wires.<br />
This completes the Project. Please mail me with your feedback. It will really encourage me to give you more & more project like this.</div>

Build very low cost FM transmitter, use your TV antenna and transmit upto 4km range!!

Here is the specification of the transmitter: No. of stage: 4 Frequency of operation: About 100MHz Antenna type: Folded 300 ohms dipole...

CadSoft Eagle Professional 7.5.0 Full

Sunil Jadhavar LED Projects 4:13 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: justify;">
Professional CadSoft Eagle 7.5.0 (82.78 MB) is a comprehensive tool for PCB design, since the scheme and ending with the creation of the card and its traces. The program has a fairly large library of standard electronic components and is quite common.</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiySZMl_GOketnGVbJJEut4eAEEJV5SnugR2mJQxdFvI1B8g-2-wvwWSbF23gODG2PzwwlKAj65JcbPu7YwVjYoZRgscb3LfuywhONrPzo_PH-_TBbvNJkOFLf9kjMFrX7XGVg3dF5lB0g/s1600/CadSoft+Eagle+Professional+7.5.0+Full.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiySZMl_GOketnGVbJJEut4eAEEJV5SnugR2mJQxdFvI1B8g-2-wvwWSbF23gODG2PzwwlKAj65JcbPu7YwVjYoZRgscb3LfuywhONrPzo_PH-_TBbvNJkOFLf9kjMFrX7XGVg3dF5lB0g/s320/CadSoft+Eagle+Professional+7.5.0+Full.png" width="252" /></a></div>
<h3 style="text-align: left;">
The program includes :-</h3>
<ul style="text-align: left;">
<li>Unit plans a creative concepts module. At an interface that is easy to use, the grid for aligning components and power lines, the picture elements on the sheet.</li>
<li>PCB Layout Editor publisher. You can place components on the future of the PP, no error checking, additional lines to simplify manual tracing means for applying the silkscreen printing on PCB.</li>
<li>Autorouter module for automatic routing of the circuit board. A large number of settings allows you to improve the quality of autorouting.</li>
<li>Library Library Editor very flexible and convenient editor.</li>
</ul>
<div style="text-align: justify;">
A major advantage of professional packaging allocates a full synchronization of the development of the project. For example, if you change or delete a component in the diagram, it is immediately reflected in the figure of the board. In programs such as ACCEL EDA, P-CAD and OrCAD must constantly monitor the entire project, with minor modifications, anytime. In addition, the restoration of the eagle (UNDO) is possible for a certain number of shares (which does not allow even the most powerful to date CAD ACCEL EDA) .</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The standard package also includes a module that validates the electrical circuit connections (ERC Electrical Rule Check) and proper arrangement of components on the motherboard (DRC Design Rule Check). And the last two operations look much better than in the most advanced systems. EAGLE validates the design and connections so that users do not know that it is involved in some strange device. Note that users must not run across a variety of software modules, as is done in P-CAD or ACCEL EDA all conversions performed in the program itself. There is also the opportunity to fill the space given polygon.</div>
<br />
Download: <a href="http://www.hitfile.net/aClZ" target="_blank">Hitfile</a> <a href="http://salefiles.com/guwdzh8578e6/Eagle_750.zip.html" target="_blank">Salefiles </a></div>

CadSoft Eagle Professional 7.5.0 Full

Professional CadSoft Eagle 7.5.0 (82.78 MB) is a comprehensive tool for PCB design, since the scheme and ending with the creation of the c...

CadSoft EAGLE PCB Design Software

Sunil Jadhavar LED Projects 3:40 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: justify;">
Electrical wires are fixed onto the board, connecting a central processor to other components on the board. Nearly all electronic devices contain one or even more printed circuits boards.<br />
<br />
The award winning EAGLE is a powerful and flexible <a href="http://www.cadsoftusa.com/eagle-pcb-design-software/about-eagle/" target="_blank">PCB design software</a> offering high level functionality of expensive commercial circuit board design software at a fraction of the cost for over 20 years. EAGLE is easy to learn, easy to use and easy to buy.<br />
<br />
It runs on Linux, Mac and Windows and allows feature enhancement, such as simulation, data import and export and self defined commands, through User Language Programs (ULPs) which are partly integrated in EAGLE and available at the <a href="http://www.cadsoftusa.com/download-eagle/" target="_blank">download area</a>.<br />
<br />
EAGLE offers DesignLink, an automated connection to the database from Premier Farnell to search and find parts from within the EAGLE design environment without ever having to leave it. The innovative PCB services interface integrated in EAGLE enables users to receive quotes and order their prototypes from high quality manufacturers on mouse click.</div>
<h3 style="text-align: left;">
EAGLE includes the following modules:</h3>
<ol style="text-align: left;">
<li><a href="http://www.cadsoftusa.com/eagle-pcb-design-software/schematic-editor/" target="_blank">Schematic Editor</a></li>
<li><a href="http://www.cadsoftusa.com/eagle-pcb-design-software/layout-editor/" target="_blank">Layout Editor</a></li>
<li><a href="http://www.cadsoftusa.com/eagle-pcb-design-software/autorouter/" target="_blank">Autorouter</a></li>
</ol>
<div style="text-align: justify;">
For further information about EAGLE’s most recent features please click here</div>
</div>

CadSoft EAGLE PCB Design Software

Electrical wires are fixed onto the board, connecting a central processor to other components on the board. Nearly all electronic devices ...

Best of Free 10 PCB Design Software

Sunil Jadhavar LED Projects 3:35 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: justify;">
<i><b>Do you need a free PCB design software or tool to put in practice the new electronic project you’ve just designed? So, we present you 10 of the best PCB software tools available on the internet that will help you to develop your printed circuit board faster and with ease. See the list under these ads.</b></i></div>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><b>0 ∴ <a href="http://bit.ly/1sTDoBC" target="_blank">PCBWeb Designer</a></b><br />
<br />
<div style="text-align: justify;">
PCBWeb is a free CAD application for designing and manufacturing electronics hardware. Design multi-sheet schematics with our fast and easy-to-use wiring tool. Route multi-layer boards with support for copper pours and DRC checking. Integrated Digi-Key Parts Catalog with Bill of Materials Manager.</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEie__A35x8BuEJwK2CJ3YGnJnbtb5iR1FPPjBB6801LfBR6IcgMFne9BmGsaR4QnLb0QSFgCDSuWtud_FqBIxJV565KiUsfAL46icYlHGsU6nQlpYNgCn40mrEkH71fI3omByb7MEYhy3s/s1600/pcbweb-designer.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="306" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEie__A35x8BuEJwK2CJ3YGnJnbtb5iR1FPPjBB6801LfBR6IcgMFne9BmGsaR4QnLb0QSFgCDSuWtud_FqBIxJV565KiUsfAL46icYlHGsU6nQlpYNgCn40mrEkH71fI3omByb7MEYhy3s/s640/pcbweb-designer.png" width="640" /></a></div>
<div style="text-align: justify;">
<br /></div>
</td>
 </tr>
</tbody></table>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><b>1 ∴ <a href="http://www.zenitpcb.com/" target="_blank">ZenitPCB</a></b><br />
<br />
Is an excellent pcb layout design software tool to create professional printed circuit board ( PCB ). It is a flexible easy to use CAD program, which allow you to realize your projects in a short time. With ZenitPCB Layout is possible to create the project starting both from the schematic capture or by the layout itself.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj7W1StBks0eLTk86eohCWyxUu-51K2VGyzBU1xkBSBETkThJDrF0wp3Ah_eUa8tuoDtLS0uXsYB8ovKBp7grTY8JgtFQuFG6wxliuWtFFE29rGj8d805q9Dz32Fw5My5VzGbi0iv2bpYw/s1600/zenitpcb.gif" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="478" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj7W1StBks0eLTk86eohCWyxUu-51K2VGyzBU1xkBSBETkThJDrF0wp3Ah_eUa8tuoDtLS0uXsYB8ovKBp7grTY8JgtFQuFG6wxliuWtFFE29rGj8d805q9Dz32Fw5My5VzGbi0iv2bpYw/s640/zenitpcb.gif" width="640" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
</td>
 </tr>
</tbody></table>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><b>2 ∴ <a href="http://tinycad.sourceforge.net/" target="_blank">TinyCAD</a></b><br />
<br />
<div style="text-align: justify;">
Is a program to help you draw circuit diagrams. It comes complete with symbol libraries to get you started straight away. As well as being able to simply print your designs, you can use TinyCAD to publish your drawings by copying and pasting into a Word document or saving as a PNG bitmap for the web.</div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="text-align: justify;">
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiE47ZSf15DntJdYuIXDNu0nr-zVnvIEkhAVHIR0MevTDquAUdZZSLajW7CxP12ldghFGJMRK6S8Mz56jDAQvnz6TKPgKxmJoML_NBdbkw9bp-SgLUbqewOV9gbAXwnwJD4TVMTSmo7UBI/s1600/tinycad.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="460" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiE47ZSf15DntJdYuIXDNu0nr-zVnvIEkhAVHIR0MevTDquAUdZZSLajW7CxP12ldghFGJMRK6S8Mz56jDAQvnz6TKPgKxmJoML_NBdbkw9bp-SgLUbqewOV9gbAXwnwJD4TVMTSmo7UBI/s640/tinycad.png" width="640" /></a></div>
<br /></div>
</td>
 </tr>
</tbody></table>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><b>3 ∴ <a href="http://www.osmondpcb.com/" target="_blank">Osmond PCB</a></b><br />
<br />
Is a flexible tool for designing printed circuit boards. It runs on Macintosh. Its many features include: virtually unlimited board sizes, number of board layers, number of parts, support for both through-hole and surface mount parts and more.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEieVT9YlxDzth-tpNfjwS1DPBqV0mC21JLKz4rjqCThXGhiCX_8vr991u79tkpW_J83pCbKn7GIpA0zbHqed-MadHuSFa6heKvQv9QCTMKkZU4k4W6eawh6y3_wBMGrhgqWV4Y4qIvhPfA/s1600/osmond-pcb-design-software.gif" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="488" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEieVT9YlxDzth-tpNfjwS1DPBqV0mC21JLKz4rjqCThXGhiCX_8vr991u79tkpW_J83pCbKn7GIpA0zbHqed-MadHuSFa6heKvQv9QCTMKkZU4k4W6eawh6y3_wBMGrhgqWV4Y4qIvhPfA/s640/osmond-pcb-design-software.gif" width="640" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
</td>
 </tr>
</tbody></table>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><b>4 ∴ <a href="http://www.suigyodo.com/online/e/index.htm" target="_blank">BSch3V</a></b><br />
<br />
Is a schematic capture program for Windows. The name “BSch” is an abbreviation of “Basic Schematic”. It has only basic functions, in order to simplify operation.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhzsG9CRINX1T89r6PT9YRYRGhzcxVQj0ednvLzTUT8pBJYMkQCZfZfK8reoZdAgRFaW49XUkSR76m19s98Xg8H0CLD1Bazj1b_27xsTQC_NTWjoxkt3-fB4CCa_3plhzOcjZy9ppyajUE/s1600/bs3vscrn-pcb-layout-software.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhzsG9CRINX1T89r6PT9YRYRGhzcxVQj0ednvLzTUT8pBJYMkQCZfZfK8reoZdAgRFaW49XUkSR76m19s98Xg8H0CLD1Bazj1b_27xsTQC_NTWjoxkt3-fB4CCa_3plhzOcjZy9ppyajUE/s1600/bs3vscrn-pcb-layout-software.png" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="text-align: justify;">
<br /></div>
</td>
 </tr>
</tbody></table>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><span class="number">5</span> ∴ <b class="titlu"><a href="http://www.electroschematics.com/832/expresspcb-download/" target="_blank" title="expressPCB">ExpressPCB</a></b><br />
<br />
Is a snap to learn and use. Laying out PCBs is easy, even for the first time user.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2-GTRSbC6HzNDHaBucXR3i-haPrvefXwACd1vihsEOehHWpc9TyOyUikq6tMucsHQJuHvhIitMNjPqWOkjXZaLwnUyirO9Gsrn7Eu-jw846cMLG4CWZUWlus-Bw1PcJw4o2RfFir1dQQ/s1600/expresspcb.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="502" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2-GTRSbC6HzNDHaBucXR3i-haPrvefXwACd1vihsEOehHWpc9TyOyUikq6tMucsHQJuHvhIitMNjPqWOkjXZaLwnUyirO9Gsrn7Eu-jw846cMLG4CWZUWlus-Bw1PcJw4o2RfFir1dQQ/s640/expresspcb.jpg" width="640" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="text-align: justify;">
<br /></div>
</td>
 </tr>
</tbody></table>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><span class="number">6</span> ∴ <b class="titlu"><a href="http://www.kicad-pcb.org/" rel="nofollow" target="_blank">Kicad</a></b><b class="titlu"> </b><br />
<br />
Is an open source (GPL) software for the creation of electronic 
schematic diagrams and printed circuit board artwork. It is useful for 
everybody working in electronic design (schematic diagrams and Printed 
Board up to 16 layers).<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhzj5DYDwOSLxkp-bVfEVj4U2_HGAnqXou1OvOLjcv8LJviOdRllc1LnTGnCxWsRsOE9wHIcomodDmoFgnxhF2KYFAY3k7wEoYfD3ZAG_P9netHXZA9T7I2W-5S83jOh4Eo4fiN17Ids8U/s1600/kicad-layout-design.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhzj5DYDwOSLxkp-bVfEVj4U2_HGAnqXou1OvOLjcv8LJviOdRllc1LnTGnCxWsRsOE9wHIcomodDmoFgnxhF2KYFAY3k7wEoYfD3ZAG_P9netHXZA9T7I2W-5S83jOh4Eo4fiN17Ids8U/s1600/kicad-layout-design.png" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
</td>
 </tr>
</tbody></table>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><span class="number">7</span> ∴ <b class="titlu"><a href="http://www.gpleda.org/" rel="nofollow" target="_blank">gEDA</a></b><br />
<div style="text-align: justify;">
Runs on Linux and has produced tools which are used for electrical 
circuit design, schematic capture, simulation, prototyping, and 
production. Currently, the gEDA project offers a mature suite of free 
software applications for electronics design, including schematic 
capture, attribute management, bill of materials (BOM) generation, 
netlisting into over 20 netlist formats, analog and digital simulation, 
and printed circuit board (PCB) design layout. </div>
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiaFv2OEixiaNJjFF_WBFIwxINH9JRKEX8tA1KggZF2Nif-P_djIT1__wskOdzZuO4hnU3F2Q5N12luAmzlGn7LwI1h_1OfbZiEato0mkc1Y_8NWYZ7iQYF2hmgd9ftoTUe-6eVj2ZOllY/s1600/geda-pcb-software.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="539" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiaFv2OEixiaNJjFF_WBFIwxINH9JRKEX8tA1KggZF2Nif-P_djIT1__wskOdzZuO4hnU3F2Q5N12luAmzlGn7LwI1h_1OfbZiEato0mkc1Y_8NWYZ7iQYF2hmgd9ftoTUe-6eVj2ZOllY/s640/geda-pcb-software.png" width="640" /></a>
</div>
<div style="text-align: justify;">
<br /></div>
</td>
 </tr>
</tbody></table>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><b>8 ∴ <a href="http://fritzing.org/" target="_blank">Fritzing</a></b><br />
<br />
<div style="text-align: justify;">
Fritzing software is an interesting open-source initiative to support designers, artists, researchers and hobbyists to work creatively with interactive electronics and develop electronic projects. Fritzing helps you learn more about electronic circuits, to document your projects and even let’s you prepare them for production. </div>
<br />
<div style="text-align: justify;">
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZK0JL8sxqep-6RGvJ5yD68UiMJecjFxH7qwoPywDeQvUlZ0xUtNYv6oQwMs7c43A0xTUvSQkcuHPM4SUlAcehYw5RFW5gkshYAPmE4MG2JfaJ3Wwoy5tNg_frGyGNUYm-Td-Ss1KvyAo/s1600/fritzing-software-pcb-view.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="366" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZK0JL8sxqep-6RGvJ5yD68UiMJecjFxH7qwoPywDeQvUlZ0xUtNYv6oQwMs7c43A0xTUvSQkcuHPM4SUlAcehYw5RFW5gkshYAPmE4MG2JfaJ3Wwoy5tNg_frGyGNUYm-Td-Ss1KvyAo/s640/fritzing-software-pcb-view.jpg" width="640" /></a></div>
<br /></div>
</td>
 </tr>
</tbody></table>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><b>9 ∴ <a href="http://www.designspark.com/eng/page/designspark-pcb-home-page" target="_blank">DesignSpark PCB</a></b><br />
<br />
<div style="text-align: justify;">
DesignSpark PCB is the world’s most accessible electronics design software. Easy to easy to learn and easy to use, it is designed to significantly reduce your concept-to-production time. At the core of this unique approach is a powerful software engine that enables you to capture Schematics, design PCB boards and layouts.</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbU-Go5h2ZWR3qrQhfAKlRmgXpe6aL1_iHs69QqEA1xfHZQy8FUDv9byY7Mzw-graDTOZf4AHhe_8OWfB8UJS5sd-fRfEG59B5JH80A9BM3yyQHaFsLHbMtqgFNFhjNc5JOg4z8RXkD7A/s1600/designspark-pcb.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbU-Go5h2ZWR3qrQhfAKlRmgXpe6aL1_iHs69QqEA1xfHZQy8FUDv9byY7Mzw-graDTOZf4AHhe_8OWfB8UJS5sd-fRfEG59B5JH80A9BM3yyQHaFsLHbMtqgFNFhjNc5JOg4z8RXkD7A/s640/designspark-pcb.jpg" width="640" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="text-align: justify;">
<br /></div>
</td>
 </tr>
</tbody></table>
<table border="1" cellpadding="3" cellspacing="3" style="background-color: #ededed; border-collapse: collapse; border: 1px solid #DDDDDD; color: black; width: 100%;">
 <tbody>
<tr>
  <td><b>10 ∴ <a href="https://easyeda.com/" target="_blank">EasyEDA</a></b><br />
<br />
<div style="text-align: justify;">
EasyEDA is a free, zero-install, Web and cloud-based EDA tool suite, integrating powerful schematic capture, mixed-mode circuit simulation and PCB layout in a seamless cross-platform browser environment, for electronic engineers, educators, students and hobbyists. </div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg42wiioh_d-Qiqk7N5QFigEpdQijaoyYmbK__qagbSg8UZnUUeJobJaJR0GXVwXSujjCkDTcR-qd2xAslvjixZDyGtm1DYtJtj2LCzdkDWpv4r04VzDVLf_zvxh2nvxf7P4mUnFqRnNgk/s1600/easyeda.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="500" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg42wiioh_d-Qiqk7N5QFigEpdQijaoyYmbK__qagbSg8UZnUUeJobJaJR0GXVwXSujjCkDTcR-qd2xAslvjixZDyGtm1DYtJtj2LCzdkDWpv4r04VzDVLf_zvxh2nvxf7P4mUnFqRnNgk/s640/easyeda.png" width="640" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="text-align: justify;">
<br /></div>
</td>
 </tr>
</tbody></table>
</div>

Best of Free 10 PCB Design Software

Do you need a free PCB design software or tool to put in practice the new electronic project you’ve just designed? So, we present you 10 o...

Free PCB Design CAD Software

Sunil Jadhavar LED Projects 2:53 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: justify;">
The ExpressPCB CAD software is very easy to learn and use. For the first time, designing circuit boards is simple for the beginner and efficient for the professional. Best of all, its FREE.</div>
<div style="text-align: justify;">
Our electronics design software includes two applications, one for drawing schematics, the other for PCB layout.</div>
<div style="text-align: justify;">
<table border="0" cellpadding="3" cellspacing="3" style="background-color: white; border-collapse: collapse; border: 0px solid #FFFFFF; color: black; width: 100%;">
 <tbody>
<tr>
  <td style="text-align: center;"><span style="color: #0b5394;"><b>ExpressPCB</b></span></td>
  <td style="text-align: center;"><b><span style="color: #0b5394;">ExpressSCH</span></b></td>
 </tr>
<tr>
  <td><div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwAtuCJlrS6W35E1aWNHoccMAJBZKaTFKqDwqQC94v9QfCSrWsezNcZO7cElLTq6R86vQpc2CDfYf8ct6jHzFpTwfehRlAHWubgCcsf8To3JKbT42ECDMrlBSRAtCtf-NkwnejW10Gvn4/s1600/expresspcb.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="249" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwAtuCJlrS6W35E1aWNHoccMAJBZKaTFKqDwqQC94v9QfCSrWsezNcZO7cElLTq6R86vQpc2CDfYf8ct6jHzFpTwfehRlAHWubgCcsf8To3JKbT42ECDMrlBSRAtCtf-NkwnejW10Gvn4/s320/expresspcb.jpg" width="300" /></a></div>
</td>
  <td><div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCf1OkUSvs2Av5V5ZMoyGi5y0ZUD6tXT4u0FHKD52iikLhSzc10XPmNEeLNY-bP_KghtT0Via3uAb_UcthNGkOvbrEjLngmPUyzkrzgxDesTfI64KTyEnEioQMjntN6pA_p3F9lGAGfao/s1600/expresssch.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="249" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCf1OkUSvs2Av5V5ZMoyGi5y0ZUD6tXT4u0FHKD52iikLhSzc10XPmNEeLNY-bP_KghtT0Via3uAb_UcthNGkOvbrEjLngmPUyzkrzgxDesTfI64KTyEnEioQMjntN6pA_p3F9lGAGfao/s320/expresssch.jpg" width="300" /></a></div>
</td>
 </tr>
</tbody></table>
<div style="text-align: justify;">
Both programs are completely free, fully functional and easily installed with a single InstallShield setup program. They run under Microsoft Windows NT, 2000, XP, Vista, Windows 7, 8.1 and Windows 10.</div>
<div style="text-align: justify;">
Learning to use our software is fast because of its standardized Windows user interface. After spending the few minutes to learn one, the other takes almost no time because it works the same way.</div>
<div style="text-align: justify;">
(Should you choose not to keep our software on your system, simply uninstall it using Add or Remove Programs found in your computer’s Control Panel.)</div>
<div style="text-align: justify;">
<a href="http://www.expresspcb.com/ExpressPCBBin/ExpressPCBsetup_7_3_4.zip" target="_blank"><b>Download ExpressPCB 7.3.4</b></a></div>
</div>
</div>

Free PCB Design CAD Software

The ExpressPCB CAD software is very easy to learn and use. For the first time, designing circuit boards is simple for the beginner and eff...

PIC Controlled Relay Driver

Sunil Jadhavar LED Projects 6:47 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: justify;">
<b><span style="font-size: large;">Project Summary</span></b></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
This circuit is a relay driver that is based on a PIC16F84A microcontroller. The board includes four relays so this lets us to control four distinct electrical devices. The controlled device may be a heater, a lamp, a computer or a motor. To use this board in the industrial area, the supply part is designed more attentively. To minimise the effects of the ac line noises, a 1:1 line filter transformer is used.</div>
<div style="text-align: justify;">
Project Description</div>
<h3 style="text-align: justify;">
The components are listed below.</h3>
<ol style="text-align: left;">
<li>1 x PIC16F84A Microcontroller</li>
<li>1 × 220V/12V 3.6VA (or 3.2VA) PCB Type Transformer (EI 38/13.6)</li>
<li>1 x Line Filter (2×10mH 1:1 Transformer)</li>
<li>4 × 12V Relay (SPDT Type)</li>
<li>4 x BC141 NPN Transistor</li>
<li>5 × 2 Terminal PCB Terminal Block</li>
<li>4 × 1N4007 Diode</li>
<li>1 × 250V Varistor (20mm Diameter)</li>
<li>1 x PCB Fuse Holder</li>
<li>1 × 400mA Fuse</li>
<li>2 × 100nF/630V Unpolarized Capacitor</li>
<li>1 × 220uF/25V Electrolytic Capacitor</li>
<li>1 × 47uF/16V Electrolytic Capacitor</li>
<li>1 × 10uF/16V Electrolytic Capacitor</li>
<li>2 × 330nF/63V Unpolarized Capacitor</li>
<li>1 × 100nF/63V Unpolarized Capacitor</li>
<li>1 × 4MHz Crystal Oscillator</li>
<li>2 × 22pF Capacitor</li>
<li>1 × 18 Pin 2 Way IC Socket</li>
<li>4 × 820 Ohm 1/4W Resistor</li>
<li>1 × 1K 1/4W Resistor</li>
<li>1 × 4.7K 1/4W Resistor</li>
<li>1 × 7805 Voltage Regulator (TO220)</li>
<li>1 × 7812 Voltage Regulator (TO220)</li>
<li>1 × 1A Bridge Diode</li>
</ol>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEic-wlam7BP6EITuWkDeodhs-BFQAWnGc10bYcKh-Tt3K29eQt8ixxCTuBY6kOFTeqRuBzgyAkn_i6O2LQIPqm4m6chMxLAAtS5pT18nyDz5bYQd2AP8S-mrg5gkjQMHSQ70Qkj8mKEHks/s1600/PIC-Controlled-Relay-Driver-PCB-1325614892.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEic-wlam7BP6EITuWkDeodhs-BFQAWnGc10bYcKh-Tt3K29eQt8ixxCTuBY6kOFTeqRuBzgyAkn_i6O2LQIPqm4m6chMxLAAtS5pT18nyDz5bYQd2AP8S-mrg5gkjQMHSQ70Qkj8mKEHks/s1600/PIC-Controlled-Relay-Driver-PCB-1325614892.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><i><b><span style="font-size: small;">Figure 1 </span></b></i></td></tr>
</tbody></table>
<div style="text-align: justify;">
The transformer is a 220V to 12V, 50Hz and 3.6VA PCB type transformer. The model seen in the photo is HRDiemen E3814056. Since it is encapsulated, the transformer is isolated from the external effects.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
{mosgoogle}A 250V 400mA glass fuse is used to protect the circuit from damage due to excessive current.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
A high power device which is connected to the same line may form unwanted high amplitude signals while turning on and off. To bypass this signal effects, a variable resistor (varistor) which has a 20mm diameter is paralelly connected to the input.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
Another protective component on the AC line is the line filter. It minimises the noise of the line too. The connection type determines the common or differential mode filtering.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The last components in the filtering part are the unpolarized 100nF 630V capacitors. When the frequency increases, the capacitive reactance (Xc) of the capacitor decreases so it has a important role in reducing the high frequency noise effects. To increase the performance, one is connected to the input and the other one is connected to the output of the filtering part.</div>
<div style="text-align: justify;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7kZVK79p6isZoKPcE1q3n47HqmsMYkwYyS3HbOJHcvFpnXC0x556uoCUeNp0ieZNAPU7m6F4ViWqIvx-4tyk4W7fysPo2QSsX3zq4MhokNEKDtIIWnAbbc5Htsb9Vr0XP5e-GqIymhBk/s1600/PIC-Controlled-Relay-Driver-Final-1325614893.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7kZVK79p6isZoKPcE1q3n47HqmsMYkwYyS3HbOJHcvFpnXC0x556uoCUeNp0ieZNAPU7m6F4ViWqIvx-4tyk4W7fysPo2QSsX3zq4MhokNEKDtIIWnAbbc5Htsb9Vr0XP5e-GqIymhBk/s1600/PIC-Controlled-Relay-Driver-Final-1325614893.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><i><b><span style="font-size: small;">Figure 2 </span></b></i></td></tr>
</tbody></table>
<div style="text-align: justify;">
After the filtering part, a 1A bridge diode is connected to make a full wave rectification. A 2200 uF capacitor then stabilizes the rectified signal.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The PIC controller schematic is given in the project file. It contains PIC16F84A microcontroller, NPN transistors, and SPDT type relays. When a relay is energised, it draws about 40mA.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
As it is seen on the schematic, the relays are connected to the RB0-RB3 pins of the PIC via BC141 transistors. When the transistor gets cut off, a reverse EMF may occur and the transistor may be defected. To overcome this unwanted situation, 1N4007 diodes are connected between the supply and the transistor collectors.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
There are a few number of resistors in the circuit. They are all radially mounted.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
Example C and HEX code files are included in the project file. It energises the next relay after every five seconds.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
Y. Erol</div>
<table style="width: 100%;">
              <tbody>
<tr>
                <th>File Name</th><th>File Size</th>
              </tr>
<tr>
                <td><a href="http://s.eeweb.com/members/circuit_projects/projects/2012/01/03/PIC-Controlled-Relay-Driver-1325614890.rar">Schematic, Layout and PCB files</a></td><td>399.01 KB</td>
              </tr>
</tbody></table>
</div>

PIC Controlled Relay Driver

Project Summary This circuit is a relay driver that is based on a PIC16F84A microcontroller. The board includes four relays so this le...

Circuit Project: Wireless Doorbell

Sunil Jadhavar LED Projects 6:39 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: justify;">
The first thing you will notice is the clever circuitry. Some of the design goes against everything we have learnt in electronics. That’s why we have to study other people’s designs and realise “the more you know, the more you realise you don’t know.” The oscillator circuit is very interesting, but first we will look at the RF oscillator. The doorbell operates on the 303MHz band and the 30 metre range (100ft) is obtained without the use of an antenna! The circuit is actually radiating from the printed track of the tank circuit. The Tank Circuit is a single-turn coil and a small capacitor (5p & 4p in parallel).</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbJt5y4eW5y_saMg7vhz0gJ3WZXnza1wHExNKOGMpAvX3vE2lcyfuBFxAGqxvbOINmkcHWHNzLkflFJ-Z5iQdxi2z5L3ZSftECUqH1Ekjt7Z9agTt8Jz6Hy6SNe2LmvcRZ_AGP7td9R9c/s1600/WirelessDoorbell-Tx-1366990010.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbJt5y4eW5y_saMg7vhz0gJ3WZXnza1wHExNKOGMpAvX3vE2lcyfuBFxAGqxvbOINmkcHWHNzLkflFJ-Z5iQdxi2z5L3ZSftECUqH1Ekjt7Z9agTt8Jz6Hy6SNe2LmvcRZ_AGP7td9R9c/s1600/WirelessDoorbell-Tx-1366990010.gif" /></a></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
In this project we show how to add a small antenna to the circuit to get double the range – plus two other improvements to increase the range. Some of the improvements will load the circuit and alter the frequency at which it operates. Others can be done without any effect on the circuit. Fortunately, the transmitting stage is what we call “tight” and is not affected by surrounding “stray capacitance.”</div>
<div style="text-align: justify;">
Normally, this stray capacitance is a persons hand or body, touching or coming near the transmitting (output) stage and altering the frequency.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The circuit has been kept near the power rails by the use of a choke in the positive rail. The positive rail is then reflected to the negative rail via the battery. This feature helps us when we want to add an antenna. A 7cm length of tinned copper wire is connected to the collector of the transistor and bent around the board so that everything can be put back into the case. When the project was tested inside the authors house, the range was increased to double. When the transmitter was taken outside, the range was over 60 metres (200ft) and the full range could not be tested as the sound from the doorbell was too faint to be heard!</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
We can learn so much from a product that is already on the market. Firstly, you know it works, it is reliable and you know what can be built for $10.00. Secondly, you know what type of components can be purchased cheaply and what to expect from them. In this case the transmitting transistor has the highest gain – so they have taken a special effort to get a good quality transistor. Now, let’s look at the transmitter circuit:</div>
<h3 style="text-align: justify;">
THE TRANSMITTER CIRCUIT:</h3>
<div style="text-align: justify;">
The transmitter circuit is made up of two building blocks – the 303MHz RF oscillator and the 32kHz crystal controlled oscillator. The 303MHz oscillator consists of a self-oscillating circuit made up of the coil on the PC board and a 9p (9 puff) capacitor (actually 4p and 5p in parallel). The circuit starts-up by the transistor producing noise. This rising-and-falling signal on the collector is passed to the parallel tuned circuit (the tank circuit) and the base sees a very smooth sinewave at a frequency of 303MHz.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
This sinewave is then amplified by the transistor and this is how the 303MHz frequency is generated. Now we come to the purpose of the 15microhenry choke on the tank circuit. When the circuit oscillates, it takes a larger and small amount of current. .</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
This current passes through the choke and the turns produce a back-emf or back voltage that fights against the flow (change) in current. The end effect is a voltage created at the point where the choke is connected to the track-work on the board. This effectively allows the track work to produce a waveform and since the frequency of this wave is very high, a percentage of the energy is radiated into the air as electromagnetic energy. The choke allows the track-work to effectively rise and fall while providing a very low resistance path for the flow of current during certain parts of the cycle.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The second building block is the crystal oscillator. This is made up of a two-stage DC coupled amplifier with feedback via the 2n2 and crystal. If the crystal is removed, the oscillator is seen as producing very narrow spikes with a frequency determined by the 2n2, as shown in the diagram below:</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidjjN8bV97fRpMPWRdFJeRh-OmmV7l9vuhWb622OUMwJ0y4bayKG58YJ5C80Lociv5atFPUtWDbEDILXbf63oyEkXEtLRwG7YkJP1tCVJ00HtJMfTy6eUV13cyANvLyxEl3yWsEfIi5zw/s1600/OscillatorWaveform-1366990010.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="114" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidjjN8bV97fRpMPWRdFJeRh-OmmV7l9vuhWb622OUMwJ0y4bayKG58YJ5C80Lociv5atFPUtWDbEDILXbf63oyEkXEtLRwG7YkJP1tCVJ00HtJMfTy6eUV13cyANvLyxEl3yWsEfIi5zw/s320/OscillatorWaveform-1366990010.gif" width="320" /></a></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
When the crystal is added, the frequency increases (because the effect of the 2n2 and crystal in series creates a lower capacitance than 2n2) and as it rises, the amplitude of the feedback signal increases until it reaches a maximum at the resonant frequency of the crystal. The crystal exhibits the lowest impedance (the highest capacitance) at the resonant frequency. This is how the circuit stabilizes at the frequency of the crystal. When the device is turned on, the 150k on the base of the second transistor turns the transistor on.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The third transistor has 0.65v on the collector and the base also receives very close to 0.65v, via the 220k resistor. The third transistor is not fully turned on and it produces a small amount of noise. This noise is passed to the second transistor and appears on the collector. The collector passes this noise to the base of the third transistor and the noise very rapidly increases to a maximum. It comes to a point where the waveform above is generated and the reason why the spikes are so narrow is easy to explain.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
When the middle transistor changes from an OFF state to an ON state, the capacitor will be partially charged and the voltage on the end connected to the base of the third transistor will drop about 6v and put a negative voltage on the base of the third transistor. This will keep it off and the middle transistor will be kept ON via the 150k base-resistor. The capacitor will gradually charge in the opposite direction via the 220k and 150k and when the base of the third transistor sees about 0.6v, it begins to turn ON.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
This causes the middle transistor to turn OFF and the collector voltage rises. This causes the capacitor to charge and create a current-flow in the base of the third transistor. Both transistors are now turned ON and the capacitor charges very quickly via the 12k and base-emitter junction of the third transistor. This creates the very narrow high-period in the waveform. When the push button is pressed, the circuit produces a 303MHz carrier with a 32kHz tone. The receiver detects the 32kHz and turns on a SOUND chip.</div>
<h3 style="text-align: justify;">
THE RECEIVER CIRCUIT :</h3>
<div style="text-align: justify;">
The receiver circuit consists of a number of stages and we will go through each one separately.</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi_wmWPVZIqe7F908tMPIpB2s5PExWheZpmRYBlhOWiFz0xI5qx4Jaz1qfcGnTBaSBVwAU-UeZ5Jm0S6Xs-UPlmUfiSm7C7z1dWw58Ma-zpgfyjcdzeAMgesytPWAD7DaeNvzSc6vWqZMY/s1600/WirelessDoorbell-Rx-1366990010.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi_wmWPVZIqe7F908tMPIpB2s5PExWheZpmRYBlhOWiFz0xI5qx4Jaz1qfcGnTBaSBVwAU-UeZ5Jm0S6Xs-UPlmUfiSm7C7z1dWw58Ma-zpgfyjcdzeAMgesytPWAD7DaeNvzSc6vWqZMY/s1600/WirelessDoorbell-Rx-1366990010.gif" /></a></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The first stage is actually a 303MHz oscillator that is operating all the time. It produces a clean 303MHz signal and this frequency is too high to be detected or processed by the 4069 chip, as the chip will only operate to about 1MHz. The theory behind using this type of stage is quite simple. It is easier to “upset” or modify a stage that is already oscillating, rather than get a non-oscillating stage to begin oscillating.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
There are all sorts of electromagnetic radiation at 300MHz and the 2-turn coil picks up all this noise. The 303MHz oscillator is firstly set into operation by the noise produced by the transistor and this is passed to the tank circuit made up of the 2-turn coil and 2p capacitor as a parallel tuned circuit. The transistor keeps amplifying this until it gets to a stabilized point where the collector is producing “hash” (junk) of about 300mV. When the transmitter is activated, the receiver circuit will detect a signal as small as a few micro-volts and the 32kHz signal will be included with all the other noise. There is a little bit more behind this receiving stage, than first meets the eye.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The stage is actually a transmitter, but we will still call it the receiver circuit. Yes, it is a very weak transmitter and it fills the surrounding with a clean 303MHz signal. When the 303MHz signal from the transmitter enters this space, the signals interfere with one another and the receiver takes more and less current as it tries to maintain the signal strength. When the 32kHz signal is present, the receiver takes a varying current that corresponds to the 32kHz signal and this is how the receiver circuit produces the waveform to correspond to the 32KHz.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
A low-impedance path to the 0v rail is provided for the emitter by using a 82uH choke and a 2n2 capacitor across a 560R resistor. This low impedance path is needed so that the transistor has a high gain. The circuit is put into very delicate oscillation by using a 1k5 from the positive rail. It operates from 3v and the current taken by this stage is less than 1mA.</div>
<h3 style="text-align: justify;">
THE BRASS TUNING-SLUG:</h3>
<div style="text-align: justify;">
The coil in the tank circuit is tuned via a brass screw (or slug or core). This is alters the frequency at which the circuit operates, when it is turned via a small screwdriver. At 303MHz, you cannot use a ferrite core as it will completely absorb the magnetic radiation produced by the coil and prevent the circuit operating. Another choice is air. If you use an air cored coil, you can use a trimmer capacitor to adjust the frequency. A cheaper approach is to use a brass core. Brass has a permeability very close to air (µ0 is the permeability of free space) and it has very little effect on concentrating the magnetic lines of flux or moving them apart.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
Materials that cause the lines of flux to move farther apart, resulting in a decrease in magnetic flux density compared with a vacuum, are called diamagnetic. Materials that concentrate magnetic flux by a factor of more than one but less than or equal to ten are called paramagnetic; materials that concentrate the flux by a factor of more than ten are called ferromagnetic. However, at very high frequencies, such as 303MHz, the magnetic flux causes eddy currents to flow in the brass and this decreases the available flux so that inserting a brass core causes the frequency to drop. This is how the receiver is tuned to exactly the same frequency as the transmitter.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The most critical capacitor in the receiver is the 2p. This sets the frequency. The 4p is merely a feedback capacitor. The 2n2 and 1n are called “pass” capacitors and allow high frequency signals to pass through them. The 1n actually keeps the positive and negative rails rigid while the 2n2 prevents the emitter moving up and down when amplifying the 303MHz signal. The signal on the collector passes to the first input of the chip via a 5k6 resistor and 1n (pass capacitor). A lot of the high frequency component is removed with the 1n capacitor connected to the 0v rail.</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhs6dTl51rPA8ZO4W-leQC9_1jkBDzadVrLrVI37egaNlHN3Un1_YUiWCV9JzDAS0X0ntvJW_MbXEliksVT-5j5bArNrZScLHmflSinxKkHKGmeNm3vCLOcG0xB_763k6k4JAytsqM9oDE/s1600/4069-1366990010.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhs6dTl51rPA8ZO4W-leQC9_1jkBDzadVrLrVI37egaNlHN3Un1_YUiWCV9JzDAS0X0ntvJW_MbXEliksVT-5j5bArNrZScLHmflSinxKkHKGmeNm3vCLOcG0xB_763k6k4JAytsqM9oDE/s1600/4069-1366990010.gif" /></a></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The first inverter has a 1M connected between the output and input to set it to mid rail so it becomes a high-gain amplifier. The second and third inverters also amplify the signal and on pin 6 we have a signal greater than 0.6v containing a lot of noise and an identifiable 32kHz waveform. The 32kHz crystal only allows the 32kHz signal to pass and the base of the transistor sees a very clean signal. Any other frequencies will not appear on the base of the transistor. The 32kHz is further amplified with two more stages and appears at pin 10 of the chip.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
It is then passed to a diode pump that charges a 47u electrolytic. Normally, this electrolytic is uncharged and pin 8 is HIGH. The PNP transistor is not turned on and the sound chip is silent.</div>
<div style="text-align: justify;">
But when the electrolytic charges, the transistor turns on and the sound chip operates.</div>
<h3 style="text-align: justify;">
GOING FURTHER:</h3>
<div style="text-align: justify;">
One of the main reasons for presenting this project is to show how to get the best range from a transmitter. Normally you need very expensive equipment to help you, but a very clever alternative is to use our method. All you have to do is place the receiver about 15 metres from the transmitter and in a very poor reception area. The aim is to get the receiver to be at the extreme end of the range so that if you move the transmitter away by as little as a metre, the receiver will not detect the signal. Now the receiver is a very sensitive RF indicator. By moving the transmitter to different places, the receiver should not detect the signal.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
You are now ready to add an antenna to the transmitter and determine its effectiveness.</div>
<div style="text-align: justify;">
We have already mentioned the transmitter circuit is classified as “tight” and adding an antenna should not shift the frequency.</div>
<h3 style="text-align: justify;">
ADDING AN ANTENNA</h3>
<div style="text-align: justify;">
The 7cm antenna is added to the point where the choke touches the PC coil on the board.</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgMhrTzR3Km66m0GbdcX9OBtvAwGi6aOptlPHqaG1aDb88FWSM8TDK50x20qp0SAfqhZkll0OeYs6DDFVJRvlQPQImJxJrsnkrlknjUHph3EdO4JyWUQDBr79jFZz0f4fxWy7QBzZApCeE/s1600/WirelessDoorbell-PCB-1366990011.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgMhrTzR3Km66m0GbdcX9OBtvAwGi6aOptlPHqaG1aDb88FWSM8TDK50x20qp0SAfqhZkll0OeYs6DDFVJRvlQPQImJxJrsnkrlknjUHph3EdO4JyWUQDBr79jFZz0f4fxWy7QBzZApCeE/s1600/WirelessDoorbell-PCB-1366990011.gif" /></a></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
Adding the 7cm antenna:</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
This point is highly active but it does not interfere with the operation of the circuit, when the antenna is connected. Bend the wire around the edge of the board and about 0.5cm above it and test the transmitter. You should get an increase in the range, up to double. If the range does not increase appreciably, the receiver may not be tuned exactly to the transmitter. To do this, adjust the brass screw in the tank circuit of the receiver. Before making any adjustment, make sure you know the original position by noting the alignment of the slot. Only turn the screw about 15° in either direction and take a “field test.” If the range reduces, you know the screw has been turned in the wrong direction.</div>
<h3 style="text-align: justify;">
INCREASING THE OUTPUT:</h3>
<div style="text-align: justify;">
Another thing that will increase the output of the transmitter involves rewiring the LED. At the moment the LED is in series with the positive rail of the transmitter. This effectively drops about 1.7v and the circuit only gets 7.3v from a fresh battery. By connecting the LED between the positive and 0v rail, with a 470R load resistor, the transmitting section will see 9v and this will increase the range. One more thing that will increase the output is to add a 220R across the 220R emitter resistor of the transmitter transistor. This increased the range in our prototype, but the frequency-adjusting screw on the receiver had to be turned about 15° clockwise to compensate for the slight change in frequency.</div>
<div style="text-align: justify;">
<b><br /></b></div>
<div style="text-align: justify;">
<b>PARTS LIST Wireless Doorbell :</b></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
1 – 220R resistor</div>
<div style="text-align: justify;">
1 – 470R</div>
<div style="text-align: justify;">
1 – 7cm tinned copper wire</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
If you want to build this project using your own components, but do not have the 32kHz crystals, here is a modification that does not need them:</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQ8bQ2Lf26D_Yrwd2YC_m9Dtr6RTdV62RBn3SIB7gzYXuSY4CAPf1C9NGFyXm5uK_NnQ4RhFpSNLKxQkCjbRBWFeckIJgQJ9kzzmUnS0jDR_3rOi3SHdVRgjyildJIu0i7S0sf1K9TzfQ/s1600/WirelessDoorbell-Rx-1366990010.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQ8bQ2Lf26D_Yrwd2YC_m9Dtr6RTdV62RBn3SIB7gzYXuSY4CAPf1C9NGFyXm5uK_NnQ4RhFpSNLKxQkCjbRBWFeckIJgQJ9kzzmUnS0jDR_3rOi3SHdVRgjyildJIu0i7S0sf1K9TzfQ/s1600/WirelessDoorbell-Rx-1366990010.gif" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQ8bQ2Lf26D_Yrwd2YC_m9Dtr6RTdV62RBn3SIB7gzYXuSY4CAPf1C9NGFyXm5uK_NnQ4RhFpSNLKxQkCjbRBWFeckIJgQJ9kzzmUnS0jDR_3rOi3SHdVRgjyildJIu0i7S0sf1K9TzfQ/s1600/WirelessDoorbell-Rx-1366990010.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQ8bQ2Lf26D_Yrwd2YC_m9Dtr6RTdV62RBn3SIB7gzYXuSY4CAPf1C9NGFyXm5uK_NnQ4RhFpSNLKxQkCjbRBWFeckIJgQJ9kzzmUnS0jDR_3rOi3SHdVRgjyildJIu0i7S0sf1K9TzfQ/s1600/WirelessDoorbell-Rx-1366990010.gif" /></a></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
The only components you will have to know how to make are the coils. The size, shape and wire diameter are important as the frequency is very high and the coil must be identical to those in the doorbell products we bought for this article.</div>
</div>

Circuit Project: Wireless Doorbell

The first thing you will notice is the clever circuitry. Some of the design goes against everything we have learnt in electronics. That’s ...

Door bell circuit using IC NE555

Sunil Jadhavar 6:23 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: justify;">
<b><span style="font-size: large;">Description </span></b></div>
<div style="text-align: justify;">
<b><span style="font-size: large;"> </span></b></div>
<div style="text-align: justify;">
The main part of this doorbell circuit are two NE555 timer ICs.When some one presses switch S1 momentarily, the loud speaker sounds a bell tone as long as the time period of the monostable multivibrator built around IC1.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
When the switch S1 pressed, IC1 is triggered at its pin 2 and output pin 3 goes high for a time period previously set by the values of POT R4 and POT R5.When the output ofIC1 goes high it resets IC2 and it starts to oscillate to make a bell sound through the speaker.The IC2 is configured as an astable multivibrator whose oscillation frequency can be varied with the help of POT R5.By adjusting the values of R4 & R5, modifications on the tone are possible.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
<b><i>If you are not familiar with the basics of 555 timer IC, and its applications, you can buy books that will help you get a better understanding from our online store. Totally 3 books have been reviewd in detail along with their authors. You can get their reviews and buy them here:- 3 Great Books to Learn 555 Timer Circuits and Projects</i></b></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
Circuit diagram with Parts list.</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJ_UQsX32h1lsdkNNZoHSyfr49a9WKd5UcoWqY_xbw7IMrquekWSKZnV_n1XcYrchciTDjqa-oeBytfEcb6e4eK1Da60cezlOg1ezfqFTliHssd3t4W3TArTuHzOa1JfRXqgE888uIVV8/s1600/door-bell-circuit-using-ne555.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJ_UQsX32h1lsdkNNZoHSyfr49a9WKd5UcoWqY_xbw7IMrquekWSKZnV_n1XcYrchciTDjqa-oeBytfEcb6e4eK1Da60cezlOg1ezfqFTliHssd3t4W3TArTuHzOa1JfRXqgE888uIVV8/s1600/door-bell-circuit-using-ne555.JPG" /></a></div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
<span style="font-size: large;"><b>Notes.</b></span></div>
<ul style="text-align: left;">
<li>The circuit has to assembled on a good quality PCB or common board.</li>
<li>The IC1 & IC2 has to be mounted on IC holders.</li>
<li>Power the circuit from a 9V battery or 9V DC power supply.</li>
<li>Switch S1 is push button switch.</li>
</ul>
</div>

Door bell circuit using IC NE555

Description The main part of this doorbell circuit are two NE555 timer ICs.When some one presses switch S1 momentarily, the loud sp...

Grommes-Precision-Frazier G-101A, F-106C 20 dBW power amplifier, 4 6GT5 schematic

Sunil Jadhavar 3:12 AM

Grommes-Precision-Frazier G-101A, F-106C 20 dBW power amplifier, 4 6GT5 schematic

Source : - angelfire.com/vt/audio/

100W LM3886 Parallel Stereo Power Amplifier

Sunil Jadhavar 3:04 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div class="schematic_text" style="text-align: justify;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-slNYGIXYtY9T1KfLl_sPnxYDpZSlNUrx2KmtgnMIeW8sOZo-Od_cO1fwTCF4ATjyUGrlX-4ANntZSslCQsF4POiZHM6seDx10qpOGUwcWhdtXyFhEkRfT43GJk0facwbBNwhySffoLA/s1600/pa100-6.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="133" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-slNYGIXYtY9T1KfLl_sPnxYDpZSlNUrx2KmtgnMIeW8sOZo-Od_cO1fwTCF4ATjyUGrlX-4ANntZSslCQsF4POiZHM6seDx10qpOGUwcWhdtXyFhEkRfT43GJk0facwbBNwhySffoLA/s200/pa100-6.jpg" width="200" /></a>This amplifier is based on the PA100 parallel amplifier detailed in National Semiconductor's application note - AN1192. Since my DIY speaker is 4-ohm and somewhat difficult to drive, I want to have a more powerful amplifier to match with it. Therefore I designed this amplifier which uses two LM3886 per channel, in parallel circuit. This amp can deliver about 50W into a 8-ohm speaker and 100W into a 4-ohm speaker. This is a stereo amplifier and therefore 4 LM3886s are used. The LM3886 circuit is in a non-inverted configuration, so the input impedance is determined by the input resistor R1, i.e. 47k. The 680 ohm and 470pF resistor capacitor filter network is used to filter out the high frequency noise at the RCA input. The 220pF C4 and C8 capacitors are used to shot out the high frequency noise at the LM3886 input pins. I used high quality audio grade capacitors at several locations: 1uF Auricap at the input for DC blocking, 100uF Blackgate for C2 and C6, and 1000uF Blackgate at the supply filter. </div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="387" src="http://electronics-diy.com/schematics/1000/PA100_schematic.gif" width="400" /></div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
The PCB is designed in a way that the power ground is separated from the signal ground, as you can see from the below layout. The signal ground is located in the middle and surrounded by the power ground. There is a thin trace near C5 connecting them. The PCB layout is done by using PADS PowerPCB 5.0. I think it is a powerful layout software. After finished the layout, I send it to a PCB manufacturer in HK to make the PCB. After the PCB is made, I found some of the drill holes are not large enough.... I have to make it bigger manually. </div>
<div class="schematic_text" style="text-align: justify;">
<div style="text-align: justify;">
Finished PCB. </div>
<br />
The 20k and 1k resistors are hand matched to 0.1%. For the output resistors, I used six 0.5W 1% 1ohm resistors in parallel per 3886 output instead of one 3W resistor because 3W 1% resistors are hard to find. <br />
<br />
I used the insulated version - LM3886 TF, so that I can mount it directly to the case and heat sink with thermal compound. <br />
<br />
Coupling capacitor is Auricap 1uF 450V. I used this high quality capacitor because it is in the main signal path. <br />
<br />
The HF filter capacitors are Silver Mica 47pF and 220pF. <br />
<br />
The power supply filter used is Blackgate 1000uF 50V. <br />
<br />
C2 and C6 are Blackgate 100uF 50V. For better result, the bi-polar version should be used. However I am not using it because the bi-polar blackgate is too big to fit into my PCB. <br />
<br />
The 680 ohm + 470pF filter network is installed at the RCA. This help filtering the high frequency noise before it gets onto the board. <br />
<br />
The WIMA 0.1uF supply decoupling capacitors are soldered directly on the pins of LM3886 at the back of the PCB. This helped to remove some high frequency noise. <br />
<br />
The 3886 are mounted on a 3/8 inch aluminum plate then to the case. Outside of the case I used 3 PC CPU heatsinks. I used Arctic Silver thermal compound between the aluminum layers to improve heat conductivity. <br />
<br />
With all these big heatsinks, it only get slightly warm when listen at normal volume. <br />
<br />
The power supply used is a regulated power supply. I used 10000uF per rail before the LT1083 regulator. After the regulator, I have 100uF on the regulator board. The advantage of using regulator is that the power supply ripple voltage is removed. If power regulation is not used, I can hear very little 50/100Hz hum from the speaker. <br />
<h3>
Power Supply Schematic : </h3>
The high current MUR860 diode is used to ensure high current flow. <br />
<br />
The voltage regulator used is LT1083, it can provide about 8A of current. <br />
<br />
Transformer used here is a 500VA 2x 25V. The power supply is then regulated by 2 LT1083, after the regulation, the voltage is 30V. <br />
<br />
Will consider to use this supply circuit instead, the TIP2955 is capable of providing 15A of current : <br />
<br />
I did some DC measurement and the result is quite good, I got 7 mV of DC offset at the speaker terminal. The voltage difference between the output of the 2 chips is less then 1 mV. <br />
<br />
The sound of this amplifier is similar to my LM3875 amplifier, which is very clean and detail. It has no hum, no hiss and no noise. Compared to the LM3875 Gainclone, this amp can deliver twice the power to my 4-ohm speaker, and it improves the dynamics and bass punch a lot.<br />
</div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="266" src="http://electronics-diy.com/schematics/1000/pa100-1.jpg" width="400" /> </div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="266" src="http://electronics-diy.com/schematics/1000/pa100-3.jpg" width="400" /> </div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="300" src="http://electronics-diy.com/schematics/1000/pa100-7.jpg" width="400" /></div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="378" src="http://electronics-diy.com/schematics/1000/DSC_7253.jpg" width="320" /></div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="266" src="http://electronics-diy.com/schematics/1000/DSC_7242.jpg" width="400" /></div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="266" src="http://electronics-diy.com/schematics/1000/pa100-4.jpg" width="400" /></div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="266" src="http://electronics-diy.com/schematics/1000/DSC_7238.jpg" width="400" /></div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="266" src="http://electronics-diy.com/schematics/1000/DSC_7239.jpg" width="400" /></div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="217" src="http://electronics-diy.com/schematics/1000/reg_PS.gif" width="400" /></div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div style="margin-left: 1em; margin-right: 1em;">
<img alt="100W LM3886 Parallel Stereo Power Amplifier " border="0" height="291" src="http://electronics-diy.com/schematics/1000/pa100_supply.gif" title="100W LM3886 Parallel Stereo Power Amplifier " width="400" /> </div>
<br />
<div style="text-align: justify;">
</div>
<div style="text-align: justify;">
</div>
</div>

100W LM3886 Parallel Stereo Power Amplifier

This amplifier is based on the PA100 parallel amplifier detailed in National Semiconductor's application note - AN1192. Since my DIY s...

Crossover For Subwoofer

Sunil Jadhavar 2:57 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: justify;">
The crossover network is intended for use when an  existing audio installation is to be extended by the addition of a  subwoofer. Often, this additional loudspeaker is one that has been lying  around for some time. If its frequency response extends down far  enough, all is well and good, but a filter is then needed to cut off any  frequencies above, say, 150 Hz. Often, a subwoofer network is an active  filter, but here this would necessitate an additional power supply. The  present network is a passive one, designed so that the speaker signal  of the existing system can be used as the input signal.<br />
<h3>
Crossover For Subwoofer Circuit diagram : -</h3>
</div>
<div style="text-align: justify;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><img alt="Crossover For Subwoofer Circuit diagram:" border="0" height="276" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFYZ_QdbNwqMAQ6ur1cY_0zzApspti3NAvqMdGtsUScA5Kw_iq0nkMO6ToHIopgZvlCU1OQokpW_cIPyYzr8rYybSg_o6X6MqSLI1QbfgjqF_GlI6cubEqQNVjuzXG54zvAzVNDN46SpJr/s320/Crossover_For_Subwoofer_Circuit_Diagram_thumb%5B4%5D.png" style="margin-left: auto; margin-right: auto;" title="Crossover For Subwoofer Circuit diagram:" width="320" /></td></tr>
<tr><td class="tr-caption" style="text-align: center;"> Crossover Circuit Diagram For Subwoofer</td></tr>
</tbody></table>
</div>
<div class="separator" style="margin-left: 1em; margin-right: 1em;">
</div>
<br />
<div style="text-align: justify;">
<br />
Since  the bass information is present in both (stereo) loudspeakers, the  signal for the sub woofer can simply be tapped from one of them. The  network is a 1st order low-pass filter with variable input (P1) and  presettable cut-off frequency (P2). The signal from the loudspeaker is  applied to terminal ‘LSP’. Voltage divider R1-R2-P1 is designed for use  with the output signal of an average output amplifier of around d 50 W.  The crossover frequency of the network may be varied between 50 Hz and  160 Hz with P2. The values of R3, P2, and C1, are calculated on the  assumption that the subwoofer amplifier to be connected to K1 has a  standard input resistance of 47 kΩ.</div>
<div style="text-align: justify;">
<br /></div>
<div style="text-align: justify;">
If this  figure is lower, the value of C1 will need to be increased slightly. It  is advisable to open the volume of the subwoofer amplifier fully and  adjust the sound level with P1. This ensures that the input of the  subwoofer amplifier cannot be overloaded or damaged. Make sure that the  ground of the loudspeaker signal line is linked to the ground of the  subwoofer amplifier. If phase reversal is required, this is best done by  reversing the wires to the subwoofer. If notwithstanding the above  additional protection is desired at the input of the subwoofer  amplifier, this is best effected by ‘overload protection ’ elsewhere in  this site.</div>
</div>

Crossover For Subwoofer

The crossover network is intended for use when an existing audio installation is to be extended by the addition of a subwoofer. Often, t...

How to Make a PWM Lamp Dimmer Using NE555

Sunil Jadhavar 8:59 PM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: justify;">
A simple and efficient PWM lamp dimmer using timer IC NE555 is discussed in this article. Yesterdays linear regulator based dimmers can only attain a maximum efficiency  of 50% and are far inferior when compared to the PWM based dimmers which can hit well over 90% efficiency. Since less amount of power is wasted as heat, the switching elements of PWM dimmers require a smaller heat sink and this saves a lot of size and weight. In simple words, the most outstanding features of the PWM based lamp dimmers are high efficiency and low physical size. The circuit diagram of a 12V PWM lamp dimmer is shown below.<br />
<br />
<i><b>We recommend 3 very good books to learn the basics and applications of the 555 timer IC. These books have been thoroughly reviewed and they can be purchased by clicking on this link:- 3 Great Books to Learn 555 Timer Circuits and Projects</b></i><br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxzme2R04UwrLKv59wfzyYxADf4LNZCryTaqWgvqrfTAljkHTAJHFS5hqK8rcjZK1nWI102WZy5PxBCLXtBBMYMnUsBsvIxDUgIu9ibbvqX44fOkGO27tvqvJMJvEEVu6EMlPOv54XWQg/s1600/pwm-lamp-dimmer-using-NE555-1.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxzme2R04UwrLKv59wfzyYxADf4LNZCryTaqWgvqrfTAljkHTAJHFS5hqK8rcjZK1nWI102WZy5PxBCLXtBBMYMnUsBsvIxDUgIu9ibbvqX44fOkGO27tvqvJMJvEEVu6EMlPOv54XWQg/s1600/pwm-lamp-dimmer-using-NE555-1.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig 1 : PWM lamp dimmer using NE555</td></tr>
</tbody></table>
As you can see, NE555 timer IC which is wired as an astable multivibrator operating at 2.8KHz forms the heart of this circuit. Resistors R1,R2, POT R3 and capacitor C1 are the timing components. Duty cycle of the IC’s output can be adjusted using the POT R3. higher the duty cycle means higher the lamp brightness and lower the duty cycle means lower the lamp brightness. Diode D1 by-passes the lower half of the POT R3 during the charging cycle of the astable multivibrator. This is done in order to keep the output frequency constant irrespective of the duty cycle. Transistors Q1 and Q2 forms a darlington driver stage for the 12V lamp. Resistor R4 limits the base current of transistor Q1.<br />
<br />
Understanding the variable duty cycle astable multivibrator.<br />
<br />
As I have said earlier, the variable duty cycle astable multi vibrator based on NE555 forms the foundation of this circuit and a good knowledge on it is essential for designing projects like this. For the ease of explanation the timing side of the astable multivibrator is redrawn in the figure below.<br />
astable multivibrator variable duty cycle<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDL9CPZnFAGLBMdsy45eEWDsYi0HoDmpNz4yRVSMVbAgXkC8tASCj6Sd03MD7dZtp4p1Sksy0uoLeNWXWHRq-HVcBZSTxHUNyM1Oi37rnEAPXRdnEW1XK7OwtLaBS4kVWYE4e5Qg-98NA/s1600/astable-multivibrator-variable-duty-cycle-2.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDL9CPZnFAGLBMdsy45eEWDsYi0HoDmpNz4yRVSMVbAgXkC8tASCj6Sd03MD7dZtp4p1Sksy0uoLeNWXWHRq-HVcBZSTxHUNyM1Oi37rnEAPXRdnEW1XK7OwtLaBS4kVWYE4e5Qg-98NA/s1600/astable-multivibrator-variable-duty-cycle-2.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig 2: Astable multivibrator with variable duty cycle</td></tr>
</tbody></table>
Upper and lower halves of the POT R3 are denoted as Rx and Ry respectively. Consider the output of the astable multivibrator to be high at the starting instant. Now the capacitor C1 charges through the path R1, Rx, and R2. The lower half of POT R3 ie; Ry is out of the scene because the diode D1 by-passes it. When the voltage across the capacitor reaches 2/3 Vcc, the internal upper comparator flips its output which makes the internal flip flop to toggle its output. As a result the output of the astable multivibrator goes low. In simple words, the output of the astable multivibrator remains high until the charge across C1 becomes equal to 2/3 Vcc and here it is according to the equation Ton =0.67(R1+Rx+R2)C1.<br />
<br />
Since the internal flip flop is set now, the capacitor starts discharging through the path R2,Ry into the discharge pin. When the voltage across the capacitor C1 becomes 1/3 Vcc, the lower comparator flips its output and this in turn makes the internal flip flop to toggle its output again. This makes the output of the astable multivibrator high. To be simple, the output of the astable multivibrator remains low until the voltage across the capacitor C1 becomes 1/3 Vcc and it is according to the equation Toff = 0.67(R2+Ry)C1. Have a look at the internal block diagram of NE555 timer shown below for better understanding.<br />
555 timer internal block diagram<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkgoyXJmx-k9TZKyqbk9S5uQzWme0sRqz2_Lk9ORQTuBJzRpDZFq_wKU7m-A0xJOGghrzh5X10TvFKuTR7nuc2WGA0iYMrNNni3faL37uWe7im9vzW5lBgbIzr9OS-TDxZES38phSb8qo/s1600/NE555-internal-block-diagram-3.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkgoyXJmx-k9TZKyqbk9S5uQzWme0sRqz2_Lk9ORQTuBJzRpDZFq_wKU7m-A0xJOGghrzh5X10TvFKuTR7nuc2WGA0iYMrNNni3faL37uWe7im9vzW5lBgbIzr9OS-TDxZES38phSb8qo/s1600/NE555-internal-block-diagram-3.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig3: NE555 internal block diagram</td></tr>
</tbody></table>
How does the frequency remain constant irrespective of the position of POT3 knob?.<br />
<br />
What ever may be the position of  POT3 knob, the total resistance across it remains the same (50K here). If anything decreases in the upper side (Rx) the same amount will be increased in the lower (Ry) and the same thing gets applied to the higher(Ton) and lower(Toff) time periods. The derivation shown below will help you to grasp the matter easily.<br />
<br />
With reference to Fig 2, we have:<br />
<br />
Ton = 0.67(R1+Rx+R2)C1<br />
<br />
Toff= 0.67(R2+Ry)C1<br />
<br />
Total time period of the output waveform “T” is according to the equation :<br />
<br />
T = Ton + Toff<br />
<br />
There fore, T = 0.67(R1+Rx+R2+R2+Ry)C1<br />
<br />
                        T= 0.67(R1+2R2+Rx+Ry)C1<br />
<br />
We know that Rx+Ry = R3<br />
<br />
There fore <b>T = 0.67(R1+2R2+R3)C1</b><br />
<br />
Therefore frequency <b>F = 1/(0.67(R1+2R2+R3)C1) </b><br />
<br />
From the above equation its is clear that the frequency depends only on the value of the components C1, R1, R2  and the over all value of R3 and it has nothing to do with the position of R3 knob.</div>
</div>

How to Make a PWM Lamp Dimmer Using NE555

A simple and efficient PWM lamp dimmer using timer IC NE555 is discussed in this article. Yesterdays linear regulator based dimmers can on...

Connecting Two or More Transistors in Parallel

Sunil Jadhavar 5:29 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
How to Connect two or more transistors in parallel<br /><br />While making power electronic circuits, configuring the power output stage correctly becomes very crucial.<br /><br />These stages primarily may consist of power devices like the power transistors or MOSFETs.<br /><br />Using power transistors are more common due to the greater ease of  configuring them. However when higher outputs are desired, it becomes necessary to add more number of these devices together.<br /><br />And as per the rules, it becomes necessary to connect them in parallel. Though using transistors in electronic circuits is pretty easy, connecting them in parallel needs some attention due to the one significant drawback with transistor characteristics.<br /><br />As per transistor specs, the devices needs to be operated under reasonably cooler conditions and that's why we install heatsinks on them to maintain the above criterion. Moreover, transistors have the "bad habit" of conducting proportionately rising currents through them as they get heated up.<br /><br />Therefore if its case temperature tends to increase, the current through it also increases, which in turn heats it up further. The process may get aggravated until the devices become too hot to sustain and gets permanently damaged. This situation is called thermal runaway, in transistors.<br /><br />When connected in parallel, due to non-consistent characteristics, the transistors in the group may dissipate varying amounts of current through them. Consequently, the transistor which passes more current through it starts getting heated up faster and pretty soon we find the device entering into the above thermal runaway situation  damaging itself and promoting the phenomenon to the remaining devices in due course of time.<br /><br />The situation can be effectively tackled by adding a small value resistor at the emitter of each transistor connected in parallel. The resistor inhibits and controls the amount of current passing through the transistors and never allows it to go to dangerous levels.<br /><br />The value should be appropriately calculated, as per the magnitude of the current passing through them.<br />How it's connected? See the figure below.<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiK3ncEjfJ5hVyyB89Zusr8pU-ysk4S55BupHpt50ZOZGYiVvC-Q_vradPFxdcb9HrCrsyX5zkU6NQZU7lsr4kCiVztGqvtmDPtE4ykou3q3ve8p5-8pRxutnuBzD1abppx7GRz6NJwQLo/s1600/How+to+Connect+Transistors+in+Parallel.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiK3ncEjfJ5hVyyB89Zusr8pU-ysk4S55BupHpt50ZOZGYiVvC-Q_vradPFxdcb9HrCrsyX5zkU6NQZU7lsr4kCiVztGqvtmDPtE4ykou3q3ve8p5-8pRxutnuBzD1abppx7GRz6NJwQLo/s1600/How+to+Connect+Transistors+in+Parallel.png" width="230" /></a></div>
<br /></div>

Connecting Two or More Transistors in Parallel

How to Connect two or more transistors in parallel While making power electronic circuits, configuring the power output stage correctly bec...

How to Make a Dual Tone Siren Circuit

Sunil Jadhavar 5:22 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
This electronic siren gives out a continuously varying high amplitude sound. Since the supply voltage is not critical, it can be used in cars, motor cycles or at home. It can replace the ordinary call bell. - . The circuit consists of two separate free running multivibrator and an oscillator.<br />
<br />
More innovative circuits HERE.<br />
<br />
A free running or astable multivibrator is one which has two quasi-stable states and the output of one stag is connected to the input of the other through a coupling capacitor.Since both the states are quasi-stable, the output attained is continuously varying in nature i.e. high, low high low-.<br />
<br />
 The output is in the form low pulses, the frequency of which depends on the base biasing resistor and the coupling capacitor, When these resistances and condensers for both the stages are of different values, the output ` wave form is rectangular; this is because the time constant of the two quasi-stable states becomes different.<br />
<br />
If this time constant of the two, states is made the same, the output obtained then is square wave. Two states of the multivibrator are made identical by the use of the same values of components.<br />
<br />
The components used in the circuit (Fig). result in a square wave output and the time constant selected is so as to give a fairly good rise and fall of the siren.<br />
<br />
However, one may change the value of coupling capacitors to get any other desired time constant. The second unit is an oscillator section. The condenser connected at the output is the feed back condenser. It determines the tone of the siren.<br />
<br />
Higher the value of the condenser the lower is the pitch. for high pitch sound (generally used in siren) feed-back condenser ranging from 0.047 uf to 0.1 mfd should be selected. The speaker may be metallic case (horn type) or small planer cone. The metallic cone horn gives better results.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj9wwMv-vrMSorOob_HJMsjBgRMqpwXmJZokGnHxpbvirywaBMTP4AmDqA5VQG0o7bBnj9mMh4J8TNgKsI-F0s9ZTD7ncNtauXbHSPYa26jMns4sLbIXkHe9TUBrxXNxBNr6dTcldhQcNY/s1600/DUAL+TONE+SIREN+CIRCUIT.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="486" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj9wwMv-vrMSorOob_HJMsjBgRMqpwXmJZokGnHxpbvirywaBMTP4AmDqA5VQG0o7bBnj9mMh4J8TNgKsI-F0s9ZTD7ncNtauXbHSPYa26jMns4sLbIXkHe9TUBrxXNxBNr6dTcldhQcNY/s1600/DUAL+TONE+SIREN+CIRCUIT.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-size: small;">Dual Tone Siren Circuit </span></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td></tr>
</tbody></table>
<h3 style="text-align: left;">
Parts for dual tone siren circuit</h3>
<div style="text-align: left;">
R1,R2,R5,R6= 22K<br />R3,R4 = 2K2<br />R7 = 10 Ohms, 1 watt<br />C1,C2,C4 = 0.1uF<br />C3 = 22uF/25V<br />T1,T2 = BC557<br />T3 = BC547<br />T4 = 2N2907 or 8550</div>
</div>

How to Make a Dual Tone Siren Circuit

This electronic siren gives out a continuously varying high amplitude sound. Since the supply voltage is not critical, it can be used in ca...

Precision Rectifier, Direct Coupled Power, CMOS Power Booster Circuit Diagrams Explained

Sunil Jadhavar 5:14 AM

<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: justify;">
The following couple of circuit diagrams provide a glimpse of the configuration for making a precision rectifier and direct coupled power source circuits. </div>
<div style="text-align: justify;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjOzFteabrqIkscpz7-naiRECYKfjUgUBi_Z6hgvcc6GVGjFT-x6wRMghbxS5V3Qdz0hec4u-qxqfEdHeQ4zDTdq7n1ikVpD9eFltNdnM6_elMsVxNYE3_3UVPnz4Sytx9nSgUaOn88fBc/s1600/Precission+Rectifier+circuit+diagram..jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="259" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjOzFteabrqIkscpz7-naiRECYKfjUgUBi_Z6hgvcc6GVGjFT-x6wRMghbxS5V3Qdz0hec4u-qxqfEdHeQ4zDTdq7n1ikVpD9eFltNdnM6_elMsVxNYE3_3UVPnz4Sytx9nSgUaOn88fBc/s1600/Precission+Rectifier+circuit+diagram..jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-size: small;">Precission Rectifier circuit diagram.</span></td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPby5dGzJS3DVQkbeL-swsHamrn3YKzYJ0xCD5H6Au2AdtnsgKesgkfoYMrp-ABffS3dYZVlxilGdOoF0SHIma3qhIWw9A55NmAa48vKEcWFRn3NgsEVojjzfX1Xn4rAFWqFarbxajVRk/s1600/Direct+Coupled+Power+Circuit+Diagram.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="394" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPby5dGzJS3DVQkbeL-swsHamrn3YKzYJ0xCD5H6Au2AdtnsgKesgkfoYMrp-ABffS3dYZVlxilGdOoF0SHIma3qhIWw9A55NmAa48vKEcWFRn3NgsEVojjzfX1Xn4rAFWqFarbxajVRk/s1600/Direct+Coupled+Power+Circuit+Diagram.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-size: small;">Direct Coupled Power Circuit Diagram</span></td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZUzWKfZFfjgAiYfAPWN4cPKTSfKDjRq7p7u7jxXpLdNr99t0Bu6iDBVsJojKq4_cN8VsSurwDUHufgyXSZ0Z4eGpA46Lt54fnE429X2kRUnjrZKX0gsrNwlh6bZbZDf4eJqp0dQoMhEw/s1600/CMOS+Power+Booster+Circuit+Diagram.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="470" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZUzWKfZFfjgAiYfAPWN4cPKTSfKDjRq7p7u7jxXpLdNr99t0Bu6iDBVsJojKq4_cN8VsSurwDUHufgyXSZ0Z4eGpA46Lt54fnE429X2kRUnjrZKX0gsrNwlh6bZbZDf4eJqp0dQoMhEw/s1600/CMOS+Power+Booster+Circuit+Diagram.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-size: small;">CMOS Power Booster Circuit Diagram</span></td></tr>
</tbody></table>
<div style="text-align: justify;">
The MC1556 operational amplifier way be used as a voltage follower ln a 
hid; amplifier application. The high input impedance avoids loading 
effects on the bridge and transforms the impedance down to a level where
 a third amplifier used in a differential mode can provide voltage gain,
 ll) in this case. The third amplifier employs the standard offset 
adjust circuit to provide nulling capability for the configuration. 
Although the circuit is shown for complementary supply voltages, , it 
lends itself well to operation from a single supply since the bridge can
 be operated iust as well from the single supply. One must, 
however,,provide for biasing the nowgrounded 100 kS2 resistor to half 
the supply voltage using a simple resistive divider. Also.- of course, 
the output is no longer referenced to ground, but to half the supply 
voltage. In the circuit the output from an LM3900 N amplifier is fed to a
 Darlington pair of power transistqrs. can deliver over three a suitable
 load when the are correctly mounted on The current·sourcing and sinking
 capability of the CA513O output stage is easily supplemented to pro- 
vide powenboost capability. ln the ' circuit three COS/MOS transistor- 
pairs in a single CA36OOE IC array are shown parallel connected with the
 output stage in the CA5l30. Jn the Class A mode of CA36OOE shown, a 
typical device consumes 20 mA of supply current at 1 5V operation. This 
arrangement boosts the current- handling capability of the CA3l3O output
 stage by about 2.5.courtesy - ETI Electronics   </div>
</div>

Precision Rectifier, Direct Coupled Power, CMOS Power Booster Circuit Diagrams Explained

The following couple of circuit diagrams provide a glimpse of the configuration for making a precision rectifier and direct coupled power ...