Voltage Regulator Circuit

November 27, 2009 By: genius

Voltage regulation means to prevent the voltage from dropping down or rising above a specific value. A 12 volt regulator circuit will provide exactly 12V under load as well as without load. On the other hand, an un-regulated 12V power supply output voltage with drop under while the load will increase and will rise when not under load. For example, an un-regulated 12V power supply can output 14V when not under load and can drop the voltage to 11V when under 1A load and 10V when under 2A load. This rise and drop of voltage in un-regulated power supplies can sometimes burn sensitive electronics equipments.
I, once, went to market to buy a voltage regulated supply but was amazed to see the cost. I decided to build my own power supply and researched a bit on the internet. My required load was 12V and 1A so I ended up designing the following voltage regulator circuit which is very low cost but at the same time it is efficient.

Voltage Regulator Circuit Diagram

Voltage Regulator Circuit Diagram

Here goes the parts list.
1. 240V to 15V 1.2A Transformer
2. 4 pieces of IN4001 (You can use a bridge rectifier as well)
3. 220uF 25V Capacitor
4. .1uF 25V Capacitor
5. 7812 IC (Integrated Circuit)
6. 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 frequency gap. The second capacitor is used as an extra filter. IN4001 rectifiers are used to convert AC current into DC current. 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.
I have successfully used this voltage regulator circuit to power up my ADSL modem. In fact, the ADSL modem was restarted every one hour or so with its original power supply but after I replaced it with this voltage regulator circuit, the modem is 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 bellow.

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24 Responses to “Voltage Regulator Circuit”

Comment from qurban ali
Time March 24, 2010 at 2:41 pm

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

Comment from Zaid
Time March 26, 2010 at 9:42 am

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

Comment from moses
Time April 8, 2010 at 5:07 am

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 electricals.my number is +23324914729 pls contact me od bless u.amen

Comment from emmanuel f. bantang, jr.
Time April 15, 2010 at 5:20 am

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.

Comment from Amy
Time April 19, 2010 at 7:52 am

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 electricals.my number is +23324914729 pls contact me od bless u.amen

Comment from omkar
Time April 22, 2010 at 8:41 pm

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

thanku very much

Comment from Ahmad
Time June 16, 2010 at 8:57 am

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.

Comment from adeoye ayinde
Time June 18, 2010 at 6:15 pm

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

Comment from vivek kulkarni
Time July 3, 2010 at 3:35 pm


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.

Comment from Seb
Time November 6, 2010 at 7:49 pm

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)?

Comment from Jun pilapil
Time December 1, 2010 at 8:28 am

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

Comment from Ross
Time January 3, 2011 at 8:13 am

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.

Comment from clara
Time March 9, 2011 at 3:36 pm

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…??

Comment from Wataka
Time April 14, 2011 at 2:29 pm

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.

Comment from kagan
Time April 16, 2011 at 2:33 pm


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


Comment from Chinedu umeano peter
Time May 17, 2011 at 8:17 pm

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.

Comment from Dipayan Das
Time June 26, 2011 at 8:05 am

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

Comment from G Fillemon
Time July 8, 2011 at 4:12 pm

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

Comment from Sunil
Time September 17, 2011 at 7:59 pm

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 sunil.rockon@yahoo.in..

Comment from edwin
Time September 29, 2011 at 10:23 am

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?

Comment from Goldi
Time August 28, 2012 at 1:14 pm

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.

Comment from lyndie
Time October 25, 2012 at 8:07 am

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.

Comment from digesh
Time January 2, 2013 at 6:36 am

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. !:):)

Comment from ameen
Time December 5, 2013 at 6:06 am

can i use this circuit to charge a rechargable battery?

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