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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
-solder
-soldering iron

Step 2: 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

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

Step 4: Now Your Done!

Now that your done you can use it for any circuit testing under 12vdc.
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:
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?
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.
 Yeah right LEDs are diodes. So we don't need the diode. BUT we need them if we have a non stable charger (PSU)...now 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.
Yar, thar be a circuit like mine instructable: <a rel="nofollow" href="https://www.instructables.com/id/Make-a-digital-logic-analyzer-for-less-than-%241/">A logc level analyzer</a><br/>
Yar me bucco, mine too!
this works good to 12v. or so with a 47 ohm resistor.
That's what I was thinking, you don't need more diodes you only need the two
what diodes did you use?
1n4001 if I remember right but it doesn't really matter.
Cool, but you really want to use macro mode on your camera. It's a little flower icon-- it helps <em>a lot</em>.<br/>
I don't think I have it it's a really cheap camera.
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 <br/><br/><a rel="nofollow" href="http://www.metacafe.com/watch/422124/digital_camera_hack_secret_the_stores_dont_want_you_to_know/">http://www.metacafe.com/watch/422124/digital_camera_hack_secret_the_stores_dont_want_you_to_know/</a><br/><br/>Ye 'Ole KipKay Digital Camera Hack. Mine has got me by for over a year now.<br/>
photos are kinda blurry
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.
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.
It's either an old idea, or his camera's clock is set wrong.
(I'd guess the latter, since he apparently made the whole thing at twenty past midnight as well.)
<sub>i don't want to sound stupid...but what's polarity?</sub><br/>
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.
Thanks, Kite~~dude~~man.
You're welcome.

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