Electronics Project Circuts: LED Projects

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

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<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>
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<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>
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<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>
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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>
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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>
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<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>
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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>
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<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>
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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>
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<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 />
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The above drawing is the copper side and below shown is the component mounting plan.</div>
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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>
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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>
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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>
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Now you need to design the dipole antenna to use with the kit.</div>
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<br /></div>
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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

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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>
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<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

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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

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<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>
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  <td><b>0 ∴ <a href="http://bit.ly/1sTDoBC" target="_blank">PCBWeb Designer</a></b><br />
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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>
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  <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 />
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  <td><b>2 ∴ <a href="http://tinycad.sourceforge.net/" target="_blank">TinyCAD</a></b><br />
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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>
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  <td><b>3 ∴ <a href="http://www.osmondpcb.com/" target="_blank">Osmond PCB</a></b><br />
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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 />
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  <td><b>4 ∴ <a href="http://www.suigyodo.com/online/e/index.htm" target="_blank">BSch3V</a></b><br />
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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 />
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  <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>
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  <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 />
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  <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>
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  <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>
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  <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;">
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  <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;">
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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

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<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%;">
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  <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>
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<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>
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<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

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<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>
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<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>
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<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>
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<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%;">
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<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

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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>
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<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>
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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>
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Normally, this stray capacitance is a persons hand or body, touching or coming near the transmitting (output) stage and altering the frequency.</div>
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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>
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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>
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THE TRANSMITTER CIRCUIT:</h3>
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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>
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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>
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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>
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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>
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<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>
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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>
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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>
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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>
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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>
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THE RECEIVER CIRCUIT :</h3>
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The receiver circuit consists of a number of stages and we will go through each one separately.</div>
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<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>
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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>
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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>
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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>
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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>
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THE BRASS TUNING-SLUG:</h3>
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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>
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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>
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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>
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<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>
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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>
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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>
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But when the electrolytic charges, the transistor turns on and the sound chip operates.</div>
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GOING FURTHER:</h3>
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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>
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You are now ready to add an antenna to the transmitter and determine its effectiveness.</div>
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We have already mentioned the transmitter circuit is classified as “tight” and adding an antenna should not shift the frequency.</div>
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ADDING AN ANTENNA</h3>
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The 7cm antenna is added to the point where the choke touches the PC coil on the board.</div>
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<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>
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Adding the 7cm antenna:</div>
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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>
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INCREASING THE OUTPUT:</h3>
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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>
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<b>PARTS LIST Wireless Doorbell :</b></div>
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1 – 220R resistor</div>
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1 – 470R</div>
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1 – 7cm tinned copper wire</div>
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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>
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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>
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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 ...

Flashing LED

Sunil Jadhavar LED Projects 7:39 PM

<span style="color: black; font-family: verdana, geneva; font-size: small;">The
 circuit is designed to use very little current to prolong battery life 
so that it can be left on permanently. A superbright’ red LED is used 
because this provides a bright flash with a low current.</span><br />

<span style="color: black; font-family: verdana, geneva; font-size: small;">If
 you want to use 4.5V supply by connecting 3 Alkaline cells or any other
 source, change the resistor along with LED from 3.3k to 1k for a better
 flash.</span><br />

<span style="color: black; font-family: verdana, geneva; font-size: small;">Note that AA cells will last longer than a 9V PP3 battery <img alt=";)" class="wp-smiley" src="http://rookieelectronics.com/wp-includes/images/smilies/icon_wink.gif" /> </span><br />

<span style="color: black; font-family: verdana, geneva; font-size: small;">To flash two LEDs alternatively we have to increase the clock pulse speed to possibly fastest to have exact proper alternation.</span><br />

<br />

<span style="color: black; font-family: verdana, geneva; font-size: small; text-decoration: underline;"><strong>Parts Required:</strong></span><br />

<ol>
<li><span style="color: black; font-family: verdana, geneva; font-size: small;">100k potentiometer</span></li>
<li><span style="color: black; font-family: verdana, geneva; font-size: small;">10k and 3.3k</span></li>
<li><span style="color: black; font-family: verdana, geneva; font-size: small;">10mF</span></li>
<li><span style="color: black; font-family: verdana, geneva; font-size: small;">LED</span></li>
<li><span style="color: black; font-family: verdana, geneva; font-size: small;">555 Timer</span></li>
<li><span style="color: black; font-family: verdana, geneva; font-size: small;">9v Battery</span></li>
</ol>
<div>
<span style="color: black; font-family: verdana, geneva; font-size: small;"><br />
</span></div>
<span style="font-size: small; text-decoration: underline;"><strong style="color: black; font-family: verdana, geneva; text-decoration: underline;">Circuit Diagram:</strong></span><br />

<div>
<span style="color: black; font-family: verdana, geneva; font-size: small;">There are three different modes to flash an LED using 555 Timer</span></div>
<span style="color: black; font-family: verdana, geneva; font-size: small;"><span style="color: black;"><img alt="" class="alignnone  wp-image-88" height="143" src="http://rookieelectronics.com/wp-content/uploads/2012/07/Flashing-LED-300x227.jpg" title="Flashing LED1" width="189" /></span><span style="color: black;"><img alt="" class="alignnone  wp-image-83" height="150" src="http://rookieelectronics.com/wp-content/uploads/2012/07/Flashing-LED2-300x227.jpg" title="Flashing LED2" width="200" /></span><span style="color: black;"><img alt="" class="alignnone  wp-image-84" height="143" src="http://rookieelectronics.com/wp-content/uploads/2012/07/Flashing-LED3-300x227.jpg" title="Flashing LED3" width="189" /></span></span><br />

<span style="color: black; font-family: verdana, geneva; font-size: small;">and their bread board arrangements</span><br />

Flashing LED

The circuit is designed to use very little current to prolong battery life so that it can be left on permanently. A superbright’ red LED i...

1-WATT LED - very good design

Sunil Jadhavar LED Projects 8:03 AM

<table border="0" id="table307" style="width: 668px;"><tbody>
<tr><td width="310"><div align="center">
     <span style="font-family: Arial;"><b>
     <img border="0" height="290" src="http://www.talkingelectronics.com/projects/30%20LED%20Projects/images/1wattLED.gif" width="325" /><br />
     <span style="color: blue;">Circuit takes 70mA on LOW brightness 
     and 120mA on HIGH Brightness</span></b></span></div>
</td>
     <td>
   <span style="font-family: Arial; font-size: x-small;">This circuit has been specially designed 
   for a 6v rechargeable battery or 5 x 1.2v NiCad cells. <b>Do not use 
   any other voltage.</b><br />
   It has many features:<br />
   The pulse-operation to the two 1-watt LEDs delivers a high current for a short 
   period of time and this improves the brightness. <br />
   The circuit can drive two 1-watt LEDs with extremely good brightness 
   and this makes it more efficient than any other design.<br />
   The circuit is a two-transistor high-frequency oscillator and it 
   works like this:<br />
   The BD139 is turned ON via the base, through the white LED and two 
   signal diodes and it amplifies this current to appear though the 
   collector-emitter circuit. This current flows though the 1-watt LED to turn 
   it ON and also through the 30-turn winding of the inductor. At the 
   same time the current through the 10R creates a voltage-drop and 
   when this voltage rises to 0.65v, the BC547 transistor starts to 
   turn ON. This robs the base of the BD139 of "turn-on voltage" and the 
   current through the inductor ceases to be expanding flux, but 
   stationary flux. </span></td>
    </tr>
</tbody></table>
<span style="font-family: Arial; font-size: x-small;">The 1n capacitor was initially pushing 
   against the voltage-rise on the base of the BC547 but it now has a 
   reverse-effect of allowing the BC547 to turn ON. <br />
   This turns off the BD139 a little more 
   and the current through the inductor reduces. <br />
   This creates a collapsing flux that produces a voltage across the 
   coil in the opposite direction. This voltage passes via the 1n 
   to turn the BC547 ON and the BD139 is fully turned OFF. <br />
   The inductor effectively becomes a miniature battery with negative 
   on the lower LED and positive at the anode of the Ultra Fast diode. The 
   voltage produced by the inductor flows through the UF diode and both 
   1-watt LEDs to give them a spike of high current. The circuit 
   operates at approx 500kHz and this will depend on the inductance of 
   the inductor. <br />
   The circuit has about 85% efficiency due to the absence of a 
   current-limiting resistor, and 
   shuts off at 4v, thus preventing deep-discharge of the 
   rechargeable cells or 6v battery. <br />
   The clever part of the circuit is the white LED and two diodes. 
   These form a zener reference to turn the circuit off at 4v. The 10k 
   resistor helps too. <br />
   The circuit takes 70mA on low brightness and 120mA on HIGH brightness via the brightness-switch. <br />
   The LEDs actually get 200mA pulses of current and this produces the 
   high brightness. </span>

1-WATT LED - very good design

Circuit takes 70mA on LOW brightness and 120mA on HIGH Brightness This circuit has been specially design...

10 LED Chaser

Sunil Jadhavar LED Projects 8:01 AM

10 LED Chaser

Here's an interesting circuit that creates a clock pulse for a 4017 from a flashing LED. The flashing LED takes almost no curre...

4 Way Traffic Lights

Sunil Jadhavar IC555 Project, LED Projects 7:54 AM

4 Way Traffic Lights

This circuit produces traffic lights for a "4-way" intersection. The seemingly complex wiring to illuminate the light...

Traffic Lights

Sunil Jadhavar IC555 Project, LED Projects 7:50 AM

<span style="font-family: Arial; font-size: x-small;"><span style="color: navy; font-family: Arial;"><span style="color: black; font-family: Arial; font-size: x-small;">Here's a clever circuit using two 555's to produce a set of traffic 
   lights for a model layout. <br />
   The animation shows the lighting sequence and this follows the Australian-standard. 
   The red LED has an equal on-off period and when it is off, the first 
   555 delivers power to the second 555. This illuminates the Green LED 
   and then the second 555 changes state to turn off the Green LED and 
   turn on the Orange LED for a short period of time before the first 
   555 changes state to turn off the second 555 and turn on the red 
   LED. A supply voltage of 9v to 12v is needed because the second 555 
   receives a supply of about 2v less than rail. This circuit also 
   shows how to connect LEDs high and low to a 555 and also turn off 
   the 555 by controlling the supply to pin 8.  Connecting the 
   LEDs high and low to pin 3 will not work and since pin 7 is in phase 
   with pin 3, it can be used to advantage in this design.  </span>
   <table border="0" id="table215" style="width: 483px;">
    <tbody>
<tr>
     <td width="63"><img border="0" height="178" src="http://www.talkingelectronics.com/projects/30%20LED%20Projects/images/TrafficLight.gif" width="38" /></td>
     <td><img border="0" height="240" src="http://www.talkingelectronics.com/projects/30%20LED%20Projects/images/TrafficLights-1.gif" width="385" /></td></tr>
</tbody></table>
</span></span>

Traffic Lights

Here's a clever circuit using two 555's to produce a set of traffic lights for a model layout. The animation shows the light...

Flashing Railroad Lights

Sunil Jadhavar IC555 Project, LED Projects 7:27 AM

Flashing Railroad Lights

This circuit flashes two red LEDs for a model railway crossing.

LEDs IN SERIES & PARALLEL

Sunil Jadhavar LED Projects 7:19 AM

<span style="font-family: Arial; font-size: x-small;"><span style="font-family: Arial; font-size: x-small;"><b><span style="color: blue; font-family: Arial; font-size: medium;">LEDs IN SERIES <br />
  </span></b><span style="font-family: Trebuchet MS; font-size: x-small;">LEDs can be placed in 
  series providing some features are taken into account. The main item to 
  include is a current-limiting resistor.<br />
  A LED and resistor is called a string. A string can have 1, 2, 3 or more 
  LEDs. <br />
  Three things must be observed:<br />
  1. MAXIMUM CURRENT through each string = 25mA. <br />
  2. The CHARACTERISTIC VOLTAGE-DROP must be known so the correct 
  number of LEDs are used in any string.<br />
  3. A DROPPER RESISTOR must be included for each string.<br />
  The following diagrams show examples of 1-string, 2-strings and 3-strings: 
  </span> <img border="0" height="255" src="http://www.talkingelectronics.com/projects/30%20LED%20Projects/images/Strings-1.gif" width="660" /><span style="font-family: Trebuchet MS; font-size: x-small;"><br />
  <br />
  </span><b><span style="color: blue; font-family: Arial; font-size: medium;">LEDs IN</span></b><span style="font-family: Arial; font-size: x-small;"><b><span style="color: blue; font-family: Arial; font-size: medium;"> 
  PARALLEL</span></b></span><span style="font-family: Trebuchet MS; font-size: x-small;"><br />
  </span><span style="font-family: Trebuchet MS; font-size: x-small;">LEDs <span style="color: red;"><b>
  CANNOT</b></span> be placed in parallel - until you read this: <br />
  LEDs "generate" or "possess" or "create" a voltage across them called 
  the
  </span><span style="font-family: Trebuchet MS; font-size: x-small;">CHARACTERISTIC VOLTAGE-DROP  
  (when they are correctly placed in a circuit). <br />
  This voltage is generated by the type of crystal and is different 
  for each colour as well as the "quality" of the LED (such as 
  high-bright, ultra high-bright etc). This characteristic cannot be 
  altered BUT it does change a very small amount from one LED to another 
  in the same batch. And it does increase slightly as the current 
  increases.<br />
  For instance, it will be different by as much as 0.2v for red LEDs and 
  0.4v for white LEDs from the same batch and will increase by as much as 
  0.5v when the current is increased from a minimum to maximum.<br />
  You can test 100 white LEDs @15mA and measure the CHARACTERISTIC 
  VOLTAGE-DROP to see this range. <br />
  If you get 2 LEDs with identical
  </span><span style="font-family: Trebuchet MS; font-size: x-small;">CHARACTERISTIC VOLTAGE-DROP, 
  and place them in parallel, they will each take the same current. This 
  means 30mA through the current-limiting resistor will be divided into 
  15mA for each LED. <br />
  However if one LED has a higher
  </span><span style="font-family: Trebuchet MS; font-size: x-small;">CHARACTERISTIC VOLTAGE-DROP, 
  it will take less current and the other LED will take considerably more. 
  Thus you have no way to determine the "current-sharing"  in a 
  string of parallel LEDs.  If you put 3 or more LEDs in parallel, 
  one LED will start to take more current and will over-heat and you will 
  get very-rapid LED failure.  As one LED fails, the others will take 
  more current and the rest of the LEDs will start to self-destruct. The 
  reason why they take more current is this: the current-limit resistor 
  will have been designed so that say 60mA will flow when 3 LEDs are in 
  parallel. When one LED fails, the remaining LEDs will take 30mA each. <br />
  Thus <b>LEDs in PARALLEL </b>should be avoided. <br />
  Diagram <span style="color: navy;"><b>A</b></span> below shows two green LEDs 
  in parallel. This will work provided the Characteristic Voltage Drop 
  across each LED is the same. <br />
  In diagram <span style="color: navy;"><b>B</b></span> the Characteristic 
  Voltage Drop is slightly different for the second LED and the first green LED will glow 
  brighter. <br />
  In diagram <span style="color: navy;"><b>C </b></span>the three LEDs have 
  different Characteristic Voltage Drops and the red LED will glow very 
  bright while the other two LEDs will not illuminate. All the current 
  will pass through the red LED and it will be damaged. <br />
  The reason why the red LED will glow very bright is this: It has the 
  lowest Characteristic Voltage Drop and it will create a 1.7v for the three 
  LEDs. The green and orange LEDs will not illuminate at this voltage and 
  thus all the current</span></span><span style="font-family: Trebuchet MS; font-size: x-small;"> 
  from the dropper resistor will flow in the red LED and it will be 
  destroyed. </span><span style="font-family: Arial; font-size: x-small;">
  <span style="font-family: Trebuchet MS; font-size: x-small;"><br />
 </span><img border="0" height="220" src="http://www.talkingelectronics.com/projects/30%20LED%20Projects/images/ParallelLEDs-1.gif" width="600" /></span></span>

LEDs IN SERIES & PARALLEL

LEDs IN SERIES LEDs can be placed in series providing some features are taken into account. The main item to include is a current-l...

Identifying a LED

Sunil Jadhavar LED Projects 7:17 AM

Identifying a LED

A LED does not have a "Positive" or "Negative" lead. It has a lead identified as the "Cathode" or Kathode...

Flashing battery monitor

Sunil Jadhavar LED Projects 5:24 AM

<div style="text-align: justify;">
<b>Description.</b></div>
<div style="text-align: justify;">
Here is a simple circuit in which an LED
 will continue flashing as long as the voltage of the battery to be 
monitored is above the set level.The transistors Q1 and Q2 are wired as a
 complementary astable multivibrator.The circuit can operate from  a 
voltage range from 6V to 12V. The voltage level at which LED has to stop
 flashing can be set by adjusting the preset R4.When the battery voltage
 reaches the threshold the flashing frequency decreases and when the 
voltage goes below the threshold the LED becomes OFF.The diode D1 is 
used to compensate the changes in the base emitter voltage of Q1 due to 
temperature changes.</div>
<div style="text-align: justify;">
<b>Circuit diagram with Parts list.</b></div>
<div style="text-align: justify;">
<b><a href="http://www.circuitstoday.com/wp-content/uploads/2009/04/flashing-battery-monitor-circuit.jpg"><img alt="flashing-battery-monitor-circuit" class="alignnone size-full wp-image-846" height="450" src="http://www.circuitstoday.com/wp-content/uploads/2009/04/flashing-battery-monitor-circuit.jpg" title="flashing-battery-monitor-circuit" width="614" /></a><br />
</b></div>
<div style="text-align: justify;">
<b>Notes.</b></div>
<ul>
<li>Assemble the circuit on a general purpose PCB.</li>
<li>Batteries from 6V to 12V can be monitored by this circuit.</li>
<li>The diode D1 must be a Schottky diode.</li>
</ul>

Flashing battery monitor

Description. Here is a simple circuit in which an LED will continue flashing as long as the voltage of the battery to be monitored is a...

Electronics Project Circuts