Simple Polarity Tester for 12v Battery

Simple Polarity Tester.  Ever encountered a problem in understanding if you’ve linked the wires right? Bored with pulling out your multimeter whenever? Need something more compact and less difficult that will help you out? In case you do, then this Instructable is for you!

Read directly to discover ways to make a very simple, reachable, and useful Polarity Tester.

Notice: Do not be afraid! You might not want to order something. The whole lot used right here may be located in old electronics and that is so easy that even beginners could make this.

For you to build a simple polarity tester, you need these ingredients:


  1. (2) LEDs (green and pink or any other colors)
  2. 4 (four) rectifier diodes (1N4007)/ another will do best
  3. One (1) 1 kilo-ohm resistor
  4. A small breadboard (optionally available)
  5. Wires
  6. A small undertaking container/enclosure
  7. Soldering iron + Solder cord
  8. Warmth reduce tubing or heat-shrink less sleeve
  9. A few screws
  10. Some cardboard or an acrylic sheet

Circuit Diagram:


polarity tester circuit diagram

The circuit for the polarity tester could be very clean, just observe the diagram at the same time as making it.

Inside the diagram, R1 represents the 1K-ohm resistor at the same time as the D3, D4, D5, and D6 constitute the diodes (1N4007). The D1 and D2 are the purple and green LEDs respectively.

Also, to make the check leads, you could use the leads from a vintage multimeter or cause them to yourself using the caps from old pens or thumbtacks (the ones with the colored plastic heads). As soon as I lead them to myself, I will place it up here; it really is a promise!

Another aspect! I did no longer use a breadboard even as making this, due to the fact I could not locate one that was small enough to in shape into my project field, but you can use a breadboard if you want to! It might make the task simpler and prevent the time it took me to reduce the wires, solder them, and then put them on the twine sleeve.

If you are the usage of an undertaking box just like mine which does not have a cowl, then use the cardboard or the acrylic sheet to make. Certainly, trace the outline of the undertaking container onto the cardboard or acrylic sheet and then cut it out. Align it with the screw holes of the mission box and use a pin (or at once the screws) to make holes inside the cardboard. Soldering iron or drill can be used to make holes in the acrylic sheet.

After finishing the circuit, enclose it on your task box and tighten the screws!

As soon as you’ve got made the circuit, check it with the aid of setting the leads on the terminals of any battery or DC power supply. If the fine test lead is saved on the advantageous terminal of the battery and the terrible lead at the bad terminal, then the green LED will mild up. The opposite will occur (i.E. The red LED will mild up) if the check leads are reversed (i.E. The nice lead on the poor terminal and the poor lead on the high-quality terminal).

polarity tester

If the LEDs do now not mild up, then:


  1. Take a look at if you have mounted them successfully.
  2. Talk over with the wiring diagram within the preceding step.

(The bad terminal of an LED is commonly at the side on which the LED is flat, as within the given picture.)

When you remedy the troubles (if there are any!), the polarity checker is ready! Please do now not be afraid to connect it to a higher voltage and current sources. I’ve connected this polarity tester up to 12V, 2.5A, and 6V, 6A and it has worked best. The diodes and the resistor supply plenty of resistance.



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