Picture of Make a simple 12 volt power supply
Have you ever needed a 12 volt power supply that can supply maximum 1 amp? But trying to buy one from the store is a little too expensive?

Well, you can make a 12 volt power supply very cheaply and easily!

I needed a 12 volt power supply for my project, the SSTC (Solid State Tesla Coil), and also made this instructable because it might be use full to someone...

Step 1: Things that you will need...

Picture of Things that you will need...
Things that you will need to make this power supply is...

  • Piece of veroboard
  • Four 1N4001 diodes
  • LM7812 regulator
  • Transformer that has an output of 14v - 35v AC with an output current between 100mA to 1A, depending how much power you will need. (I found a 16v 200mA transformer in a broken alarm clock.)
  • 1000uF - 4700uF capacitor
  • 1uF capacitor
  • Two 100nF capacitors
  • Jumper wires (I used some plain wire as jumper wires)
  • Heatsink (optional)

You should be able you get most (maybe all) of the parts at Radio Shack or Maplin.
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I ask why compute the value of the capacitor

PatrickR203 days ago

how to calculate value of capacitors, diodes and restistors to be used?

Kunal Gehlot2 months ago
You didn't tell about the volts of capacitor...
I've got 4700uF 25v
100uF 25v
1uF 63v
100uF 16v
capacitors and 15v 750mA transformer ...
Can I use them ?
If no, tell me all the components with proper specifications of them.
Thank you
HardikS12 months ago

what kind of modifications are required if i want to get current up to 3A instead 1A??

Deathadder3 months ago
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.
ShiningT3 months ago

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

i dont think you need the LED

funkyshakeel10 months ago
Can i use 103nF replace of 100nF ???


paul why they used 4700 micro farad capacitor ? any calculation for this?

@syed http://goo.gl/RSmg1Z Refer this link hopefully you get it

eli2411 year ago

hey :) what if i use a power supply with 3 amps? what do i do? do i keep the same capacitor values?

tehcmn eli2417 months ago

1uF per mA is a good rule of thumb.

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?

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.

1. It will contain 3 pins

2. Pin 1 is input can give upto 24 v dc

3. Pin 2 is common(Neative)

4. Pin 3 is output ( Positive,(load))

5. But you can withdraw only 1 Amp max only with heatsink

6. Heat sink is not neccessary if only drawn only 50% of the rated current

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.

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 ;)

If you are trying to keep 12V as 12V a Zener diode might be a better option, but that's a different implementation entirely.

arukshan6 months ago

will I get 12v 10a from this circuit if I use 12v 10a stepdown teansformer

er_ayon arukshan5 months ago

connect more transistor in parallel get more current.......high power transistor...and also used heat sink for all ic and transistor....

mathewriver5 months ago

What should I change to use batteries (24volts) instead of the transformer and get 1A out and what is the efficiency of the circuit?

ursm6 months ago

if planning to use any power supply for motors you should add a protection diode between output and input on the regulator


Can you give me a schematic and materials for 12V input voltage with an output 5V and 2A ..thank you in advance..

BUT you should reduce the transformer output to 7.5 volts.

otherwise you create too much heat reducing the input voltage

Just use 7805 voltage regulator. It gives 5v output and max of 1.5Amps.

AntonioP36 months ago

I need to convert 115volt AC 12volt 4AMP
for a refrigerator water dispenser

SivaA27 months ago

how to identfy the primary and secondary winding

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).

I agree.
A universal rule for the NatSemi 78xx is that with the model number & batch # / datecode facing toward you, every so often IGO and play with linear regulators.

merv.gower.58 months ago

hi, i have a power supply that is producing 20.00 volts and is rated at 13.8 volts x 4amps

TGRIMEAU2 years ago
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 ??
PaulJ7 TGRIMEAU9 months ago

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.

aa salam1 year ago
Is it correct the pin out of ic 7812?
PaulJ7 aa salam9 months ago

You can find the correct information from the manufactures documentation at::


Azam-Jamal1 year ago

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

PaulJ7 Azam-Jamal9 months ago

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::


Jez36510 months ago

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?

PaulJ7 Jez3659 months ago

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::


if i want say 11v at output. would it be sare to include 11v zener? pls answer needed urgent

Yes. However a 1 volt drop from a zener (ie 11vZ) can be hard to find as well as (compare) expensive to a dropping resistor. Using Ohm's law R= V / I gives you the resistance drop. P=((I*I)*r) or P=Isq times R. There are many dropping resistor calculators available on the web for free.

fkhan143 years ago
Can i Use Bridge in Replace of diode........????????? please answer me as soon as possible
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