Fixed Voltage Power Supply

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The fixed voltage power supply is useful in applications where an adjustable output is not required. This supply is simple, but very flexable as the voltage it outputs is dependant only on the regulator and transformer you choose. The maximum output current is 1.5A.


This is the schematic of the Fixed Voltage Polarity Power Supply


Total Qty.
C112200uF 35V Electrolytic Capacitor
C2, C420.1uF Ceramic Disc Capacitor
C3110uF 35V Electrolytic Capacitor
D1, D221N4007 Silicon Diode
BR112A 30V Bridge Rectifier
U11Regulator (See Notes)
T11Transformer (See Notes)
S11SPST 2 Amp Switch
F112A 250V Fuse and Holder
MISC1Heatsink For U1, Line Cord, Case, Wire


  1. Since this project operates from 120 (or 220, or 240, etc.) volts AC, it MUST be built inside a case.
  2. U1 will reauire a heatsink.
  3. You will need to choose T1 and U1 to match the voltage you want. Use the table below as a reference.

    Output Voltage
    5V6V, 1.5A7805
    6V6V, 1.5A7806
    9V12V, 1.5A7809
    12V12V, 1.5A7812
    15V24V, 1.5A7815
    18V24V, 1.5A7818

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Fixed Voltage Power Supply
Thursday, September 26, 2013 10:53:29 AM
shouldn't the T1 be at least 2V more than the required voltage?
Fixed Voltage Power Supply
Sunday, June 03, 2012 5:04:31 PM
how to generate a one volt power supply from an main ac supply.
Greg Taylor
Fixed Voltage Power Supply
Tuesday, March 06, 2012 9:53:13 AM
I am involved in a senior project that requires me to build a 6V 1.5A power supply. How can I determine what the values I need for the Fixed Voltage Power Supply schematic that is provided from your website? Your help is very much needed. Thanks.
Fixed Voltage Power Supply
Wednesday, February 01, 2012 4:58:05 AM
The 1/2/3 are the pins on the LM78xx. I have a question though. Since I'm going for 5v out, I imagine that I could replace the LM78xx with the R-785.0-1.0 from RECOM? Better efficiency but would only have 1A out, for me that's fine as it's only to power USB type devices.
Fixed Voltage Power Supply
Tuesday, January 10, 2012 10:33:50 AM
can u please tell me why 3 & 2 is written in U1
Fixed Voltage Power Supply
Saturday, December 03, 2011 4:29:18 AM
its very easy ,use ( LM7805 ) to get 5v DC power supply
Fixed Voltage Power Supply
Tuesday, October 05, 2010 11:51:28 PM
Should the Switch (S1) not be on the Positive / Live side before the transformer?
Fixed Voltage Power Supply
Saturday, August 28, 2010 9:35:00 PM
what is the purpose of D1, D2, C2, C3, and C4? And, why you didn't include resistor in the filter and for the load? thanks... hope you answer my questions ASAP...thanks again
Sandro Pace
Fixed Voltage Power Supply
Thursday, August 05, 2010 8:01:21 AM
Hi, I would like to build a power supply that can give out 24V DC at 5A from 240V AC. What parts in this circuit do I need to change to achieve this. Thanks.
variable power supply
Saturday, January 02, 2010 10:57:21 AM
ASSALAM o ALAIKUM! sir i want the circuit which regulate from 1.2 to 30 but i want that circuit having transformer whose AC input is 220 volt i have seen your circuits in your circuits AC input in the transformer is 120. plz give me the circuit as soon as possible i shall be very thank ful to u for this act of kindness
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