Research Cell
Mechanical and Electronics Related Information and DIY Projects

Simple Voltage Regulator Circuit

Voltage regulation means to prevent the voltage from dropping below or rising above a specific value. A 12-volt regulator circuit will provide exactly 12V under load or without load. On the other hand, an un-regulated 12V power supply output voltage will drop under load and rise when there is no load present.

For example, an unregulated 12V 1A power supply can output 14+V when not under load and can drop the voltage to 11V at 1.2A load and 10V at around 1.5A load. This rise and drop of voltage in un-regulated power supplies can sometimes burn sensitive electronic pieces of equipment.
A few days ago, I needed a regulated power supply so I went to the market to buy it. I was surprised to see the price tags so I decided to build a power supply myself.

12V Regulated Power Supply Circuit Diagram

Here is the power supply circuit diagram which I designed. You can download it for offline use or print this entire page to assist you while building this circuit.

Voltage Regulator Circuit Diagram
Voltage Regulator Circuit Diagram

Here goes the parts list.

  • 240V to 15V 1.2A Transformer
  • 4 pieces of IN4001 (You can use a bridge rectifier as well)
  • 220uF 25V Capacitor
  • 0.1uF 25V Capacitor
  • 7812 IC (Integrated Circuit)
  • A heat sink plate for 7812 IC

7812 is a very good voltage regulator integrated circuit (IC). It is cheap but efficient, that is why I selected it for this regulator circuit. 7812 Pin2 connections are also explained in my regulator circuit diagram. You can see that Pin 1 is input, Pin 2 is Ground (which is often –V) and Pin 3 is output. It is very simple to understand 7812. The 220uF 25V capacitor is used as a buffer to cover the frequency gap. The second capacitor is used as an extra filter. IN4001 rectifiers are used to convert AC into DC. A transformer is used to convert 240V AC into 15V AC. If you have 110V mains then you can use a 110V AC to 15 AC transformer.

Load Testing of Power Supply

I have successfully used this voltage regulator circuit to power up my ADSL modem. My ADSL modem had a habit to restart after every few hours but since I have switched to my homemade regulated power supply, my modem never restarted by itself.

Any electronic device which requires 12V 1A power can be powered by this circuit so feel free to use it. You can post your questions and comments in the comments section below.

  1. qurban ali says:

    I Have a Transformer 75+75 AC volt plz send me Voltage Regulator Circuit I Used 12+12 DC Volt For This Transformer.

  2. Zaid says:

    genious i want to regulate 24v dc to 12v dc then in this condition which circuit i use.plaese help me.thank you.

  3. moses says:

    can give me 1000 watts inverter diagram and process of building it please. i also need diagram of a solar paniel . am a student of tema technical institute and offering electricals, pls help me me cos i love number is +23324914729 pls contact me od bless u.amen

  4. emmanuel f. bantang, jr. says:

    good day sir… i appreciate most your circuit keep up the good work. please give some information or suggestions because i’am planning to avail and practice your circuit to utilized it in portable grinder, drill etc. which run by pack batteries. in response please upgrade my plans what is best and more applicable components. thanks and more power.

  5. Amy says:

    can give me 1000 watts inverter diagram and process of building it please. i also need diagram of a solar paniel . am a student of tema technical institute and offering electricals, pls help me me cos i love number is +23324914729 pls contact me od bless u.amen

  6. omkar says:

    can you give me circuit diagram of all electronic component testor with it,s full guide.s

    thanku very much

  7. Ahmad says:

    Hi! I think you are vary wel. your inverter is very good and essy. But i have a missunderstanding in this curcuit. plz Xplane pin conection of ic cd4047 as soon as posible. I will be very thankfull to you in this faver.

  8. adeoye ayinde says:

    sorry, l was so warry about to know how to repair fault power board in any pump power board. thanks

  9. vivek kulkarni says:


    what will be the circuit diagram for 12V dc regulator. we have input of 12V dc to 24V dc and current of 2A. we require constant voltage at 12V and current of 0.5A. and we have IC7812.

    please reply as early as possible.

  10. Seb says:

    Thanks for the design. Can you recommend a website or two, where I can purchase these parts (especially the 240 VAC to 15 VAC transformer)?

  11. Jun pilapil says:

    gud day i just want to ask f this type of circuit and parts can also be use in constructing a 12V 12A power supply coz i like ur circuit diagram it so ezy 2 do…i will wait for reply sir ty

  12. Ross says:

    I am trying to get a regulated 12VDC/300 mA output from a supply that varies from 18 to 27VDC. What is the input voltage tolerance of a 7812 regulator? Will it handle 27 volts? If so, your regulator circuit could be just the ticket. Thanks.

  13. clara says:

    am a beginner in circuit design
    i just wanted to knw on what basis did u select the values of the capacitors…?

    i wann design a powersupply which outputs 12v 200ma and without using a transformer this s my first task given to me ….

    can u plz help…??

  14. Wataka says:

    Thank for all the good projects you have about inverters.My question is that,can i use step down transformer to make an inverter,if it can, how can it be used.
    Can the o/p of a step down transformer be used as the input and the usual input be used as the output.
    please help me.

  15. kagan says:


    how could i get more current out of this circuit ? 5 amps current


  16. Chinedu umeano peter says:

    Good afternoon sir,please i need your help in my inverter construction,i have finish your 500watts inverter circuit diagram and i found out that it work well but i have problem in transformer.i am begging you to help me,give me formular that i will use to wind the 500watts transformer.please sir.

  17. Dipayan Das says:

    I wanted some more information about 78xx voltage regulators. SO if you please provide me with some more information about voltage regulators, then I will be happy. plz mail me.
    — Thank You

  18. G Fillemon says:

    good day sir, first I would like to thank you for the good work you have done, secondly I would like to ask you for some assistance, I need a voltage regulator that will regulate 24vdc from 240/120 trnsfrmer

  19. Sunil says:

    Thanks for this informative post Mr.genius..
    I want to design a similar circuit for my project. As you said in your post that it supplies 12V and 1A output as DC.. And i want about 100mA DC output for my design. So is it possible yo connect some resistor in series and scale down the current? Or i should use some other trick??
    your guidance will be much appreciated..
    If any one else has good idea plz contact me at

  20. edwin says:

    good afternoon sir!!

    thank you for this site,sir i have a problem regarding on my 12v, 12 ampere converter,charger power supply..when i used this on my ham radio it drops off..can i used the 7812 ic for this situation? i’d like to turn this to regulated poer supply.does your circuit can fit to my problem?

  21. Goldi says:

    Sir plz send me circuit diagram of 12 volt , 8 amp. Regulated power supply. With indicating battery full charge, batt. Low, and stop charging after batt. Get full charged.

  22. lyndie says:

    good day sir,
    can i used the 7812 as a voltage regulator to charge the battery of my motorcycle while driving?
    the design regulator was burnt so i replaced a diode only, because it is so expensive, but my battery is always damaged due to the output voltage of the diode is not regulated.

  23. digesh says:

    hi sir,
    how can i decide the secondary voltage as 15V.if i want 5V dc the value is vary or not.or other circuit remain same or not.i have to use 7805 IC for this but how can i decide the secondary voltage at transformer.and how can i decide the caacitor value? i need it.can explain this? i ll b thankfull. !:):)

  24. ameen says:

    can i use this circuit to charge a rechargable battery?

  25. golden says:

    Pls can I get a diagram circuit on how to convert a 2.5kva Gen to 3kva. My email is Thank u.

  26. Abhay Pitale says:

    I want 12 volt DC ouput , but input will be 3 phase supply. The voltage between each 2 phase is 440 volts.And want this to work without earthing. Kindly guide.

  27. kstuff says:

    good cct…..I only need a higher current than 1A……about 30A what can i do

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