Dual Polarity Power Supply

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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).

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Comments

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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.)

vinod deshmukh Dual Polarity Power Supply Wednesday, January 14, 2009 10:23:09 PM

I need dual polarity power supply cvircuit diagram without using centert tap transformer(or if possible,without using transformer i.e. 'transformerless dual power supply'

anonymous Dual Polarity Power Supply Friday, October 03, 2008 4:35:18 PM

Your C1 and C3, C2 and C4, C5 and C6, and C7 and C8 are in parallel which looks like overkill. For example, you simply have a 2201 micro Farad cap made out of C1 and C3. Was this for some purpose?
(Editor's notes: Filtering.)

anonymous Dual Polarity Power Supply Tuesday, September 09, 2008 12:45:11 PM

I only need d schematic diagram of the +15v and -15v dual power supply and the components

Simon Dual Polarity Power Supply Sunday, July 06, 2008 10:56:25 PM

Hi, I like the dual supply circuit, and would like to know if Transformer T1 has no centre tap, with the rest of the circuit remain the same, is the GND still applicable? Singapore.

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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.)
vinod deshmukh	Dual Polarity Power Supply	Wednesday, January 14, 2009 10:23:09 PM
I need dual polarity power supply cvircuit diagram without using centert tap transformer(or if possible,without using transformer i.e. 'transformerless dual power supply'
anonymous	Dual Polarity Power Supply	Friday, October 03, 2008 4:35:18 PM
Your C1 and C3, C2 and C4, C5 and C6, and C7 and C8 are in parallel which looks like overkill. For example, you simply have a 2201 micro Farad cap made out of C1 and C3. Was this for some purpose? (Editor's notes: Filtering.)
anonymous	Dual Polarity Power Supply	Tuesday, September 09, 2008 12:45:11 PM
I only need d schematic diagram of the +15v and -15v dual power supply and the components
Simon	Dual Polarity Power Supply	Sunday, July 06, 2008 10:56:25 PM
Hi, I like the dual supply circuit, and would like to know if Transformer T1 has no centre tap, with the rest of the circuit remain the same, is the GND still applicable? Singapore.