Dual Polarity Power Supply

Author	Views	Views Today	Rank	Comments
	149,797	71		78

This dual polarity power supply is easy to build, requires few parts, and is adjustable from 0-15 volts. It is great for powering op amp circuits, as well as other circuits that require a dual supply voltage.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
C1, C2	2	2200uF 35V Electrolytic Capacitor
C3, C4, C5, C7	4	1uF 35V Electrolytic Capacitor
C6, C8	2	100uF 35V Electrolytic Capacitor
R1, R4	2	5K Pot
R2, R3	2	240 Ohm 1/4 W Resistor
BR1	1	2A 30V Bridge Rectifier
U1	1	LM317 Adjustable Positive Regulator
U2	1	LM337 Adjustable Negative Regulator
T1	1	30V Center Tapped 2 Amp Transformer
S1	1	SPST 2 Amp Switch
MISC	1	Heatsinks For U1 And U2, Line Cord, Case, Knobs For Pots, Wire

Notes

Since this project operates from 120 (or 220, or 240, etc.) volts AC, it MUST be built inside a case.

U1 and U2 get quite hot and will require heatsinks. A fan is usually not needed.

You can, of course, add a volt and amp meter.

U1 and U2 can only go down to a minimum of +-1.2V. If you need to go lower, you can add two 1N4003 diodes in series with the output of the regulator. The diodes drop about 0.6V each, which will allow the supply to go to 0. Note that this will also decrease your maximum output voltage by 1.2V. (Thanks to Steve Horvath for the suggestion).

Related Circuits

Comments

Add A Comment

Opcode Dual Polarity Power Supply Monday, August 16, 2010 2:33:53 AM

Better way to go below 1.2V (well, 1.25 to be exact) is to tie the R1 pot to -1.25V (instead of ground as shown) and R4 pot to positive 1.25V.

anonymous Dual Polarity Power Supply Friday, July 30, 2010 2:32:26 AM

can you please send me a circuit diagram of a dual power supply regulator to supply currents between 0 and 1.5A to a variable load resistor at a voltage of 2 to +12V

vp_archer Dual Polarity Power Supply Friday, June 25, 2010 12:02:14 AM

the junction between capacitors: are they connected to GROUND? from the diagram i see a "dot" there, but will that cause any problem? thank you.

anonymous Dual Polarity Power Supply Monday, December 21, 2009 11:11:48 AM

I want to know about the Input, Output and Ground of U1 and U2. I mean what are 1, 2, and 3. Can you reply it to my mail? Thank you.

daphne jane peralta Dual Polarity Power Supply Friday, June 26, 2009 4:32:42 AM

nice one! i'll be making a power supply soon..

Rudianto C Dual Polarity Power Supply Monday, June 15, 2009 6:32:01 PM

Hi, I am going to built a center tap power supply + - 110VDC. Is it possible to use directly bridge diode 50A 1000V and 2 serial Capacitor 10000 uF 200V without trafo apply to electrical power 220 VAC ?

Tipu Dual Polarity Power Supply Sunday, June 07, 2009 12:14:39 PM

Would it possible to devise a Dual polarity Power Supply by using only 7812 Voltage Regulator and transistors. i.e not using LM317 and LM337.

anonymous Dual Polarity Power Supply Wednesday, March 11, 2009 6:04:50 AM

PLACE A 10uF electrolityc between pot wipers and ground. this will iprove hum rejection and Kf...I would put a 100R trimpot in series with one of the pots, because you can never get a double pot that has equal resistances on both sliders.

Mark Dual Polarity Power Supply Thursday, February 19, 2009 7:49:10 AM

How is it possible to vary voltage from 0 to 30V instead of 0 to 15V?

Jeff Dual Polarity Power Supply Tuesday, February 10, 2009 5:04:48 AM

This is the same exact circuit that the data sheet for the LM317 shows for a 1.2V - 25V power supply. This one is just using a center tapped transformer to feed the bridge. The circuit from the data sheet is copied except using, on the bottom it uses an LM337 as the regulator. The center tap is the DC circuit ground. Real original.
(Editor's notes: How odd that it's on the datasheet, as I designed this circuit some 15 years ago for a project and have never even looked at the datasheet for these ICs.)

The last 10 comments are currently shown. Show All Comments. Add A Comment

If you would like to leave a comment, you can do so using the form below. Comments can be things like suggestions, successes or failures, improvements, similar circuits, error reports, an answer to a previous commenter's question, or anything in between. However if you would like to ask a question it is suggested that you use the forum instead. The forum provides a more robust environment for discussion.

Important: If you post a technical question here, there is no guarantee it will be answered. All technical questions should be posted to the forum. The owner of this site generally does not answer questions in comments.

All comments are subject to approval before they are displayed here, so your comment will not appear immediately. This is done mainly to prevent spam and other abuse. If you wish to remain anonymous, simply enter "anonymous" for your name and/or email.

Name:
Email:
Subject:
Comments:
Anti Spam Code:	Please enter the exact text shown in the image above into the box below. Browser cookies must be enabled to comment on circuits.

Privacy Policy

Opcode	Dual Polarity Power Supply	Monday, August 16, 2010 2:33:53 AM
Better way to go below 1.2V (well, 1.25 to be exact) is to tie the R1 pot to -1.25V (instead of ground as shown) and R4 pot to positive 1.25V.
anonymous	Dual Polarity Power Supply	Friday, July 30, 2010 2:32:26 AM
can you please send me a circuit diagram of a dual power supply regulator to supply currents between 0 and 1.5A to a variable load resistor at a voltage of 2 to +12V
vp_archer	Dual Polarity Power Supply	Friday, June 25, 2010 12:02:14 AM
the junction between capacitors: are they connected to GROUND? from the diagram i see a "dot" there, but will that cause any problem? thank you.
anonymous	Dual Polarity Power Supply	Monday, December 21, 2009 11:11:48 AM
I want to know about the Input, Output and Ground of U1 and U2. I mean what are 1, 2, and 3. Can you reply it to my mail? Thank you.
daphne jane peralta	Dual Polarity Power Supply	Friday, June 26, 2009 4:32:42 AM
nice one! i'll be making a power supply soon..
Rudianto C	Dual Polarity Power Supply	Monday, June 15, 2009 6:32:01 PM
Hi, I am going to built a center tap power supply + - 110VDC. Is it possible to use directly bridge diode 50A 1000V and 2 serial Capacitor 10000 uF 200V without trafo apply to electrical power 220 VAC ?
Tipu	Dual Polarity Power Supply	Sunday, June 07, 2009 12:14:39 PM
Would it possible to devise a Dual polarity Power Supply by using only 7812 Voltage Regulator and transistors. i.e not using LM317 and LM337.
anonymous	Dual Polarity Power Supply	Wednesday, March 11, 2009 6:04:50 AM
PLACE A 10uF electrolityc between pot wipers and ground. this will iprove hum rejection and Kf...I would put a 100R trimpot in series with one of the pots, because you can never get a double pot that has equal resistances on both sliders.
Mark	Dual Polarity Power Supply	Thursday, February 19, 2009 7:49:10 AM
How is it possible to vary voltage from 0 to 30V instead of 0 to 15V?
Jeff	Dual Polarity Power Supply	Tuesday, February 10, 2009 5:04:48 AM
This is the same exact circuit that the data sheet for the LM317 shows for a 1.2V - 25V power supply. This one is just using a center tapped transformer to feed the bridge. The circuit from the data sheet is copied except using, on the bottom it uses an LM337 as the regulator. The center tap is the DC circuit ground. Real original. (Editor's notes: How odd that it's on the datasheet, as I designed this circuit some 15 years ago for a project and have never even looked at the datasheet for these ICs.)