Introduction: Simple Polarity Tester

Picture of Simple Polarity Tester

In this instructable I will show you how to make a simple polarity tester capable of out to about 12vdc.

Step 1: Materials

-4 diode (must at least withstand 12vdc)
-1 red LED
-1 green LED
-1 1k ohm resistor
-perf board
-soldering iron

Step 2: How to Know How to Position Diode on Circuit Board

Picture of How to Know How to Position Diode on Circuit Board

You should notice a white, Grey or other color banned on your diode, this is were it goes on a schematic.

Step 3: The Circuit

Picture of The Circuit

-D1=Green LED
-D2=Red LED
-D4 to 7=Diode
-R1=1 k ohm resistor

Step 4: Now Your Done!

Picture of Now Your Done!

Now that your done you can use it for any circuit testing under 12vdc.


GitarGr8 (author)2008-03-23

Cool idea, this is a great project for a beginner. I don't think that D4 through D7 are needed in this case because you are using LEDs, which are themselves a type of diode. Try building a circuit like this:

camaney (author)GitarGr82010-07-29

I need to check the polarity on batteries of 2V, 6V, 8V and 12V will this simple design will work as well or do I have to implement a switch and add different resistances value?

GitarGr8 (author)camaney2010-07-29

You'd probably want a different resistor for the various voltages and LEDs, but I don't see why this wouldn't work for what you're trying to do. you might want to add a selector switch for the different voltages you are trying to test, each with the properly sized resistor for that voltage.

agis68 (author)GitarGr82010-02-27

 Yeah right LEDs are diodes. So we don't need the diode. BUT we need them if we have a non stable charger (PSU) we replace the diodes by Zeners . For example if you work with 4,5 V the need a 5v1 zener. Zener protects and reduce the Voltage but no the Amps.

Junkyard John (author)GitarGr82008-08-12

Yar, thar be a circuit like mine instructable: A logc level analyzer

Dr.Bill (author)Junkyard John2009-04-13

Yar me bucco, mine too!

Dr.Bill (author)GitarGr82009-04-13

this works good to 12v. or so with a 47 ohm resistor.

Ben The Builder (author)GitarGr82009-04-07

That's what I was thinking, you don't need more diodes you only need the two

Sagar Gondaliya (author)2009-06-25

what diodes did you use?

1n4001 if I remember right but it doesn't really matter.

GorillazMiko (author)2008-03-23

Cool, but you really want to use macro mode on your camera. It's a little flower icon-- it helps a lot.

I don't think I have it it's a really cheap camera.

viacin (author)steven1236542008-08-24

How about a new digital camera. :-) You can find some awsome disposable ones with a lot of features for about $20, then do this to 'em :D

Ye 'Ole KipKay Digital Camera Hack. Mine has got me by for over a year now.

MACKattacksnipe (author)2008-07-09

photos are kinda blurry

computerwiz_222 (author)2008-04-17

This is essentially a fancy lighting up multimeter. This is actually a really great idea! I can't tell you how many times I will be working in my car and I want to check polarity of some wires or something.

BrianKT (author)2008-03-23

Try using macro mode on your camera next time you take pictures that close up. Btw, why do the pictures say they're from 2004? Great concept though.

Kiteman (author)BrianKT2008-03-24

It's either an old idea, or his camera's clock is set wrong.

Kiteman (author)Kiteman2008-03-24

(I'd guess the latter, since he apparently made the whole thing at twenty past midnight as well.)

lawizeg (author)Kiteman2008-04-07

i don't want to sound stupid...but what's polarity?

Kiteman (author)lawizeg2008-04-08

It's which way round the current flows (the + and - on batteries). Also, some components, like diodes (including LEDs) and some kinds of capacitor, only work when the current flows through them one and not the other.

lawizeg (author)Kiteman2008-04-08

Thanks, Kite~~dude~~man.

Kiteman (author)lawizeg2008-04-09

You're welcome.

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