Simple Polarity Tester

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Author	Views	Views Today	Rank	Comments
Dudley LeRoux	168,380	10		13

This tester can be used to check the polarity of any power source, and is therefore very useful when installing automotive equipment, alarm systems or anything else you can think of. Because this circuit is so simple and cheap, even frying one with an over voltage is not a big deal.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
R1	1	1K 1/4W Resistor
D1	1	Green LED
D2	1	Red LED
D4, D5, D6, D7	4	1N4001 Silicon Diode	1N4004, 1N4005, 1N4007
MISC	1	Board, Wire, Case, Probes

Notes

Email Dudley LeRoux with questions, comments, etc.

To use the circuit, just connect your probes to the source under test. If D1 lights up, the left most probe (on the schematic) is connected to positive. The opposite is true if the left probe is negative. If both LEDs are on, the source being probed is AC.

Be careful when using this tester not to probe a source greater than about 12V.

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Comments

Add A Comment

Adam Simple Polarity Tester Tuesday, January 31, 2012 3:37:30 PM

I'm wondering if you could use a selector switch, where the input is the node D1 and D2 share and each different output goes through a different value resistor and then into the node that D5 and D6 share. This would make it able to handle different and higher voltage ranges?

anonymous Simple Polarity Tester Monday, January 17, 2011 6:28:51 PM

simple yet effective

Michael Simple Polarity Tester Sunday, April 13, 2008 5:23:09 AM

Excellent. Used it to sucessfully add more visible large additional turn indicator light above dash board on car.

anonymous Simple Polarity Tester Monday, November 12, 2007 9:21:45 PM

thank u and many other good people on the web that share wat they make your polarity tester has made things eeser for me and works great thanks once again nick italy

anonymous Simple Polarity Tester Saturday, November 10, 2007 9:59:43 PM

Nice. However, you don't need all that rectifier! Do you? Only two, reverse parallel LEDs and resistor. So it gets even cheaper and easier to fit in a plastic pen. :-) |----------|<---------| o-----////-----| |-------------o |----------->|--------|

Rick Selva Simple Polarity Tester Friday, October 12, 2007 7:18:15 PM

I'm looking for a polaraty tester that can read plus and mines this is to check a product when is plus or minus the unit should have to probes so when i touch it if going to tell if it can out plus or minus.

moses michael d Simple Polarity Tester Tuesday, September 25, 2007 10:09:12 AM

This circuit is true but i need more explanation please.

anonymous Simple Polarity Tester Friday, September 07, 2007 10:04:32 AM

what is the probe

anonymous Simple Polarity Tester Thursday, August 02, 2007 4:25:04 AM

Found useful but why not be design to rate voltage in case the voltage is higher.

grey hog Simple Polarity Tester Friday, May 25, 2007 5:45:09 PM

you crazy specify the uses! hello polarity tester duh

anonymous Simple Polarity Tester Friday, May 18, 2007 9:16:52 AM

I had a simple tester with just a bulb and 2 wires connected to it. 1 red 1black. My grandson steped on it. Gone. This was a very handy tool for identifying the positive + wire so you wouldnt wire a device incorrectly or in reverse. The only time the bulb would lite is when the 2 wires were correctly identified. where can I find such an item? thank you for your time.

anonymous Simple Polarity Tester Saturday, May 05, 2007 4:42:19 PM

very useful allthough i used shokey diodes insted

anonymous Simple Polarity Tester Tuesday, March 13, 2007 7:35:35 AM

specify the uses

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Adam	Simple Polarity Tester	Tuesday, January 31, 2012 3:37:30 PM
I'm wondering if you could use a selector switch, where the input is the node D1 and D2 share and each different output goes through a different value resistor and then into the node that D5 and D6 share. This would make it able to handle different and higher voltage ranges?
anonymous	Simple Polarity Tester	Monday, January 17, 2011 6:28:51 PM
simple yet effective
Michael	Simple Polarity Tester	Sunday, April 13, 2008 5:23:09 AM
Excellent. Used it to sucessfully add more visible large additional turn indicator light above dash board on car.
anonymous	Simple Polarity Tester	Monday, November 12, 2007 9:21:45 PM
thank u and many other good people on the web that share wat they make your polarity tester has made things eeser for me and works great thanks once again nick italy
anonymous	Simple Polarity Tester	Saturday, November 10, 2007 9:59:43 PM
Nice. However, you don't need all that rectifier! Do you? Only two, reverse parallel LEDs and resistor. So it gets even cheaper and easier to fit in a plastic pen. :-) \|----------\|<---------\| o-----////-----\| \|-------------o \|----------->\|--------\|
Rick Selva	Simple Polarity Tester	Friday, October 12, 2007 7:18:15 PM
I'm looking for a polaraty tester that can read plus and mines this is to check a product when is plus or minus the unit should have to probes so when i touch it if going to tell if it can out plus or minus.
moses michael d	Simple Polarity Tester	Tuesday, September 25, 2007 10:09:12 AM
This circuit is true but i need more explanation please.
anonymous	Simple Polarity Tester	Friday, September 07, 2007 10:04:32 AM
what is the probe
anonymous	Simple Polarity Tester	Thursday, August 02, 2007 4:25:04 AM
Found useful but why not be design to rate voltage in case the voltage is higher.
grey hog	Simple Polarity Tester	Friday, May 25, 2007 5:45:09 PM
you crazy specify the uses! hello polarity tester duh
anonymous	Simple Polarity Tester	Friday, May 18, 2007 9:16:52 AM
I had a simple tester with just a bulb and 2 wires connected to it. 1 red 1black. My grandson steped on it. Gone. This was a very handy tool for identifying the positive + wire so you wouldnt wire a device incorrectly or in reverse. The only time the bulb would lite is when the 2 wires were correctly identified. where can I find such an item? thank you for your time.
anonymous	Simple Polarity Tester	Saturday, May 05, 2007 4:42:19 PM
very useful allthough i used shokey diodes insted
anonymous	Simple Polarity Tester	Tuesday, March 13, 2007 7:35:35 AM
specify the uses