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.

Step 1:

There are many polarity tester available in market like one above but it is just a waste of parts.

Step 2: BOM(Bill of Materials)

BOM(Bill Of Materials)

1. green led

2. red led

3. 330 ohm resistor(optional)

4. soldering iron

5. solder

Step 3: Soldering Led

solder positive terminal of green led to negitive terminal of red led and negitive terminal of green led to positive terminal of red led

Step 4: Soldering Resistor(optional)

solder 330 ohm resistor to led in series to prevent led from burning

Step 5: Enclosure

LUC VOLDERS made enclosure for this in tinkercad
http://lucstechpage.weebly.com/polarity-tester.html

Introduction: Polarity Tester

Step 1:

Step 2: BOM(Bill of Materials)

Step 3: Soldering Led

Step 4: Soldering Resistor(optional)

Step 5: Enclosure