Step 5: Test it!

After you had built your power supply, test it with your multimeter to make sure they are no solder bridges.

After you tested it, put it in a plastic box or something to protect you from shocks.
But do not operate the power supply like I did, it is very dangerous because of the mains voltage on the transformer, you or somebody will get badly shocked!

My power supply has 11.73v output, not too bad, I don't need it to be exactly 12v...
<p>pzlz post a circut diageam </p>
<p>is ke diyagram b pist kro na </p>
Please tell me how to make 12volts DC supply from USB port output of my laptop that gives 5volts output..... I want to give power to my modem(that requires 12v dc) from USB port of my laptop.
<p>use boost converter. </p>
<p>how to calculate value of capacitors, diodes and restistors to be used?</p>
<p>in a bridge converter each diode conduct only 3milisecond or 3x10^-3 sec. capacitor Q=CV. now we Know i=dq/dt or Ixt=Q</p><p>now put all in one single equation you get, </p><p>Ixt=CxV</p><p>your supply voltage is= 12v</p><p>t= 3x10^-3 sec</p><p>i= what you want </p><p>V= 12v</p><p>and you get Cap value.</p>
<p>how if it has to have an output of 24volts?</p>
<p>Desn't the LM7812 Have a 1.5AMP output?</p>
<p>how make 12 volt power supply and its connection?</p>
<p>use this! but i recommend use buck converter! </p>
<p>I ask why compute the value of the capacitor</p>
You didn't tell about the volts of capacitor...<br>I've got 4700uF 25v<br>100uF 25v<br>1uF 63v<br>100uF 16v<br>capacitors and 15v 750mA transformer ...<br>Can I use them ?<br>If no, tell me all the components with proper specifications of them.<br>Thank you
<p>what kind of modifications are required if i want to get current up to 3A instead 1A?? <br></p>
<p>use this.....</p>
<p>Can u tell me what is the resistance of resistor that u used that LED.....????plz reply as soon as possible ..... i have to made it urgent for my final project...thnkx</p>
<p>i dont think you need the LED</p>
Can i use 103nF replace of 100nF ???
<p>paul why they used 4700 micro farad capacitor ? any calculation for this?</p>
<p>@syed http://goo.gl/RSmg1Z Refer this link hopefully you get it </p>
<p>hey :) what if i use a power supply with 3 amps? what do i do? do i keep the same capacitor values?</p>
<p>1uF per mA is a good rule of thumb.</p>
<p>I am sorry if I sound new at this, but I am. I just blew a capacitor and burned my finger (lol). Instead of using a transformer I used a 12vdc adapter. I am looking to pull about 1A and your comment says 1uF/mA. What capacitors are you talking about in this comment? Could you give me some direction as to how to wire from a 12VDC adapter?</p>
<p>if you need 12 v output use 7812 ic last two digit represents the voltage so if you need 5 volt ask for 7805,simple. </p><p>1. It will contain 3 pins</p><p>2. Pin 1 is input can give upto 24 v dc </p><p>3. Pin 2 is common(Neative)</p><p>4. Pin 3 is output ( Positive,(load))</p><p>5. But you can withdraw only 1 Amp max only with heatsink</p><p>6. Heat sink is not neccessary if only drawn only 50% of the rated current</p>
<p>So you will want a 1000uF electrolytic on both the input and the output pins, with the - stripe to ground, with a 25V (or 16V) working voltage (WV). I'd be willing to bet you either put the cap in backwards or used one with a WV that was too small.<br><br>Use the circuit diagram in the article but chop off the diodes and transformer. If you are dropping 12V to 5V at 1A (I assume this is what you are doing) you'll need a heatsink. 7805s do not smell nice when they are burning ;)<br><br>If you are trying to keep 12V as 12V a Zener diode might be a better option, but that's a different implementation entirely.</p>
<p>will I get 12v 10a from this circuit if I use 12v 10a stepdown teansformer</p>
<p>connect more transistor in parallel get more current.......high power transistor...and also used heat sink for all ic and transistor....</p>
<p>What should I change to use batteries (24volts) instead of the transformer and get 1A out and what is the efficiency of the circuit?</p>
<p>if planning to use any power supply for motors you should add a protection diode between output and input on the regulator</p><p>http://www.learnabout-electronics.org/PSU/images/78xx-protection-diode.jpg</p>
<p>Can you give me a schematic and materials for 12V input voltage with an output 5V and 2A ..thank you in advance..</p>
<p>BUT you should reduce the transformer output to 7.5 volts.</p><p>otherwise you create too much heat reducing the input voltage</p>
<p>Just use 7805 voltage regulator. It gives 5v output and max of 1.5Amps.</p>
<p>I need to convert 115volt AC 12volt 4AMP <br>for a refrigerator water dispenser</p>
<p>how to identfy the primary and secondary winding</p>
<p>Some of you posters need to stay from electricity before you electrocute yourselves. Your questions prove that your are inept working with it. As for the person asking about the pinout, yes, the regulator pinout is WRONG. Hopefully anyone building this is smart enough to check the datasheet. {Pin 1 is the input, Pin 2 is ground, and Pin 3 is output).</p>
<p>I agree.<br>A universal rule for the NatSemi 78xx is that with the model number &amp; batch # / datecode facing toward you, every so often IGO and play with linear regulators.</p>
<p>I agree! if you are not in the electronics field and are senselessly playing around with transformers or capacitors, or any electronic component for that matter.....stop. Instructables is not an educational institution and being an idiot + electricity can cause heart arithmia if not death.</p>
<p>btw, using garbage components and poorly constructed pcb boards is irresponsible and half-assed.</p>
<p>you don't just drip a ton of solder onto a board and call that legit! although if you are doing that your probably dumb enough to put your fingers in your mouth and give yourself lead poisoning which will solve all of our problems</p>
<p>hi, i have a power supply that is producing 20.00 volts and is rated at 13.8 volts x 4amps </p>
I am planning to make wood portable laptops cooling fan and 12 volt power supply change to 2 volt ( red led ) and i did calculater of formula R=V/I R=( 12-2 ) / 0.015 R=( 10) / 0.015 R= 666.67 ohm resistor but no light red led with switch so try reduce to 325 ohm resisor but still weak light red led and agian try reduce to 265 ohm resistor to work bright light red led but 265 ohm resistor is still hot . Do you have any idea ??
<p>You need to know 2 items. The turn on voltage of the LED and the current consumption. The dropping resistor is based on both. Also make sure it is and LED and not some other lamp type. </p>
Is it correct the pin out of ic 7812?
<p>You can find the correct information from the manufactures documentation at::</p><p>http://www.ti.com/lit/ds/symlink/lm7805c.pdf</p>
<p>Can this circuit provides a stable filtered current like I designed one with IN4001 diodes and 12 v transformer and 330micro farad capicitor a power regulator but when ever the supply is working suddenly if any one switch on the side way switch like a bulb etc .The power fluctuate and its make the hole system attached to it off.can any one help me about the filterd current supply plz.and design etc</p>
<p>Please check the current draw of the circuit you are powering. This reads as if you have exceeded the ability of the regulator. You can find these limitations in the manufactures documentation at::</p><p>http://www.ti.com/lit/ds/symlink/lm7805c.pdf</p>
<p>Looks great but Ive got one question before I make it... What is the lowest voltage you can charge it at? Or what voltage do you charge it at?</p>
<p>If the question is:: What is the min / max voltage that can be applied to get a regulated 12vDC output the answer is in the manufactures documentation for the part. For the LM7812 the specs are found at::</p><p>http://www.ti.com/lit/ds/symlink/lm7805c.pdf</p>
<p>if i want say 11v at output. would it be sare to include 11v zener? pls answer needed urgent</p>

About This Instructable


201 favorites


Bio: &ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash; &quot;Energy cannot be created nor destroyed!&quot; &ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;&ndash;
More by Plasmana: How To Build A Simple But Powerful Flyback Driver ZVS Flyback Driver - Video Close ups on electronics
Add instructable to: