Power supply form the basic building block of any electronic circuits and therefore its important to familiarize the DC power supply circuit construction. The above given circuit illustrates a simple approach to construct a dual DC power supply of 5V and 12V from the 230V AC mains supply. The Voltage ranges 5V and 12V are widely used in all kinds of simple electronic circuits, so its meaningful to learn this simple construction.
WORKING OF DUAL POWER SUPPLY CIRCUIT:
The above circuit obtains power from a 230V AC mains supply voltage and fed into a step down transformer for transforming higher voltage supply to lower one. The transformer TR1 can be of 230V primary ,15V secondary and 1A step down transformer. The stepped down voltage can be fed into the bridge rectifier made of four 1N4004 diodes for the conversion of AC supply to DC one.
IC regulator pinout
The output from the bridge rectifier was filtered by the capacitor C1 and C2 to offer a steady DC level to the input pins of the regulators used in the above circuit. The DC voltage is then fed in to the IC 7805 which is a 5V regulator and also to the IC 7812 which was a 12V regulator. The output obtained from the 7805 & 7012 are 5V and 12V respectively. A LED D5 was connected through the current limiting resistor R1 for indicate the state of the device.
This kind of circuits are highly useful where two dual range of DC voltages are used to power the operation of a circuit. Varying the voltage regulator IC ‘s 7805 or 7812 with 7806 and 7808 to obtain 6V and 8V as output. But each IC have minimum and maximum voltage requirements, so make sure you build in such a way to meet the requirements.
Hi Frank
You have done an awesome work by providing us the schematic with PCB Design . Thank for that !!
There is one thing , I want to ask that can i add 7809 in b/w 7812 & 7809 , as i want to make Power Supply which could deliver all three outputs 12V,9V,5V
please what ic do i need to use in place of 78xx seriies ic, that will be able to deliver 2a. i am using it to build a 12v 2amps heater for my greenhouse
Hi Ponynamas,
You need not to worry about that your motor was rated as 12v so draw 12v output from the regulator and feed it to the motor. It will only draw 300mA for its operation
Hi there I have made this regulator .But I can have very descant 5 v supply but I cant get 12 v with at least 200 ma what is the problem Please advice me.
Kamal,
Well i need bit more specifications than that. Both the IC’s 7805 and 7812 are capable of supplying 1A to the load. But it all depends on the source, please state the Voltage and wattage rating of the source. If you derive from wall socket as shown in the above diagram recheck your connections and make sure every connection is right.
Clariza,
C3? i guess you mean the C2 capacitor. Capacitors are used to remove the ripples in this circuit to give a steady input to the voltage regulator IC’s. So its good to add one for stabilized operation. You can remove 7805 and C2 if you only want 12V output.
i made this circuit but, the problem is when i connect the load to the 5v output supply i get only 6V from the 12V outpit pin.
Hi Akash,
That shouldn’t be happening. What is the load you have used with the 5V, I mean the current rating of it?
Hi Frank
You have done an awesome work by providing us the schematic with PCB Design . Thank for that !!
There is one thing , I want to ask that can i add 7809 in b/w 7812 & 7809 , as i want to make Power Supply which could deliver all three outputs 12V,9V,5V
Please can I use a 230-12v 500mA transformer instead
Sommy,
Yes but your current delivering capability of the circuit will be reduced.
i’am ask to my supervisor our project,he say the circuit is false,can u explain to me sir??
Yie,
Has he pointed out any error in it?
Will it be okay if i used LM317 instead of IC 7812?
Reyna,
Yes you can, but you need to add appropriate resistors with it to derive your desired voltage.
can this supply feed 2A load?
Ammara,
No it cannot. The 78XX series IC is capable of delivering only 1A to the load.
please what ic do i need to use in place of 78xx seriies ic, that will be able to deliver 2a. i am using it to build a 12v 2amps heater for my greenhouse
Yes there are 12v 2A regulators available in the internet. http://www.nteinc.com/specs/1900to1999/pdf/nte1936.pdf Check this link out. But you may need to check whether you can find it in your region
Thanks
Couldn’t find the ic in my region. Got an idea here, https://www.instructables.com/id/Increasing-current-on-78xx-series-regulators/ , is it okay?
or can i add a transistor next to the l7 ic
increase the current gain.
I have an 18V 2A transformer. will it be ok?
Stephanie,
Yes you can
hello, i want to connect a dc motor of 12V,300mA as the load and i have 1A transformer, how can I control the current from 1A to 300mA?
Hi Ponynamas,
You need not to worry about that your motor was rated as 12v so draw 12v output from the regulator and feed it to the motor. It will only draw 300mA for its operation
Hi there I have made this regulator .But I can have very descant 5 v supply but I cant get 12 v with at least 200 ma what is the problem Please advice me.
Kamal,
Well i need bit more specifications than that. Both the IC’s 7805 and 7812 are capable of supplying 1A to the load. But it all depends on the source, please state the Voltage and wattage rating of the source. If you derive from wall socket as shown in the above diagram recheck your connections and make sure every connection is right.
Hi.. Can I removed C1,C3, 7805,. And can still be functioned?
Clariza,
C3? i guess you mean the C2 capacitor. Capacitors are used to remove the ripples in this circuit to give a steady input to the voltage regulator IC’s. So its good to add one for stabilized operation. You can remove 7805 and C2 if you only want 12V output.