Introduction: Improved Adjustable Voltage Power Supply

Hi everyone,this is my first instructable.

This is very useful when you are beginner in electronics technology.

I'm going to make an 12V adjustable voltage.You can adjust the output voltage by the potentiometer.

Minimum of 0.01mV.
Maximum of around 12V.

You will need:
*1 pc transformer 12V output with a current ranging from 100mA-2A
*8 pcs 1N4001 diodes
*2 pcs 1000uf capacitors,rated with 25V
*4 pcs 100nf capacitors,you can also used 0.1uf capacitors,rated with 16V
*2 pcs 1uf capacitors,rated with 16V
*2 pcs 470 ohm resistors,1/4 watt
*2 pcs LM7812 regulator or AN7812(the same output voltage with the LM7812)
*2 pcs LED 5mm(3V)any color you want
*2 pcs 50k potentiometer
*1 pc rocker switch
*File Case
*Fuse cartridge
*hook up wires or jumper wires
*Illustration board to make base of your project
*Printed Circuit Board

All these materials needed are available in electronics store or you can see in a radios,amplifier,etc....

Step 1:

Cut the illustration board to fit inside the file case.

Put the transformer inside the case.

Tap the fuse and switch to the transformer.

Step 2:

If you finish working of that,build the circuit now.

Here's the diagram.

Remember that you will need two PCB to build the 2 supplying circuits .

Step 3:

After building the circuits,install now inside the case.

Next is the breadboard.

Connect the wires to the +- terminals of the breadboard.Both left side and right side of the breadboard.

Step 4:

Now is the final step.

Switch on, turn each potentiometer to see if the circuit is working,you will see the LED are glowing.

Test each terminals of the breadboard,how much was the voltage of the left and right side.
If the reading is around 12V+.

Congratulations,you've made an 12V adjustable voltage supply. 


vikaskumardabas (author)2012-04-26

we can use 1k variable resistor instead 50k.
I think it will work as tested

vikaskumardabas (author)2012-04-26

we can use 1k variable resistor instead 50k.
I think it will work as tested

vikaskumardabas (author)2012-04-26

we can use 1k variable resistor instead 50k.
I think it will work as tested

vikaskumardabas (author)2012-04-26

we can use 1k variable resistor instead 50k.
I think it will work as tested

pure punjabi (author)2012-04-22

can i use a LM9211 voltage regulator instead of LM812

gomibakou (author)2011-11-04

Take care with the potentiometer. If you supply 12V at 2A (24W), surely it can't manage such power and will burn if it's a common potentiometer. You are using a potentiometer like a rheostat (power potentiometer) but they aren't intended to be used for direct power control. Usually a common pot can handle 1 or 2W (at least the common pots i know xD ).

If you want to control the voltage output then use a variable voltage regulator as the LM317 (quite common 1.5A if cooled correctly), using the pot in the ADJ pin. For more current you need K serie (LM317K), other different regulators, specific design to supply the extra current -check datasheets- or design a regulator circuit.

Furthermore the efficiency of the power supply drops using the pot in the output stage because most of the power is dissipated as heat (the psu alwys supply +12V regardless you need 1V for example, so this excess is disspated).

Resuming: that potentiometer is not well placed and could burn if you need max current at low voltage. If a shortcircuit happens you could fry your circuit because it will receive full +12V.

srain1 (author)2011-05-06

Thank You and sorry for that thing.

First,make an voltage rectifier with the use of 1N4001 diodes.
Connect the rectifier to the transformer,after that connect the other side of the rectifier to LM7812 regulator before attaching the capacitors to the regulator.

Lastly connect the potentiometer.Attach the 470ohm resistor with the LED to the center side of potentiometer,the center side of potentiometer will serve as final output of 12V supply.Connect #2 of the regulator to the left side of potentiometer,and connect the right side of potentiometer to the negative output of rectifier.also attach the negative terminals of all capacitors to the negative output of rectifier.
The 100nf cap does not have polarity,so you can interchange when installing.

SHIFT! (author)2011-05-06

Very interesting concept, but perhaps you could briefly mention how to read circuit diagrams? Personally, I've never been that good at them...