Introduction: Polarity Pen

About: I am 47 years old and I live in Brazil. I am a Telecommunication / Electronics Engineer. twenty years acting in the industry of "Telecommunication and Networking". I like everything that engages Tech…

Polarity Pen Tester - A Simplified one

This is the avery simple polarity tester for automotive systems tests and also for electronics bench.

The circuit is very simple as well as its operation. A yellow LED shows if the pen is connected to a mains supply. A red LED indicates when a probe has been connected to a positive lead in the measured system. A green LED indicates when a probe has been connected to a negative or earth in the measured system.

Of course, you can change the collors according to your "taste" .....

A black and red alligator claws connect the general power (you also can use a banana pin to do it. A male banana pin with a thin point extender for precision tests in PCB are included in the project.

The set was mounted using a pemanent ink pen. Holes were drilled for the LEDs. The wire used for the alligator claws were removed from anti-static wrist (they are very flexible). The alligator claws are connected to the banana pins....

In the next steps you will find all information you need to build the project.

Step 1: The Schematic and Components

In the Picture you can see the schematic, it is very simple to build it

The components you will need are:

3 x 1K5 (resistor);

3 x LED (5mm);

2 x alligator claws (black and red);

3 x male banana pin;

1 x extender for banana pin with fine point (optional);

1 x permanent Ink pen (used);

1 x copper PCB

1 x used permanent ink pen or witheboards marker tube;

Flexible wires;


Step 2: The PCB and Components Arrangement

You need to etch a copper PCB as shown in the picture.

Take care cause the view is from components side so you need to invert the drawning.

The circuit operates from 5V till 15V

PAD1 is connected to the POSITIVE Power Supply. PAD2 is connected to the NEGATIVE Power Supply.


LED3 Indicates if the power supply is connected;

LED2 Indicates if the test lead was connected to the positive;

LED1 Indicates if the test lead was connected to the negative

I am so sorry but the video is in my native language "Portuguese"

Any help you need use my contacts shown in the next step.

Thank you very much.

Greeting from Brazil to all people around the world.

Step 3: Further Contacts

My contact channels:
1 - Blogger:

2 - youtube:

3 - Skype: marcelo.moraes

4 - Instructables:

5 - GitHub:

5 - GitHub:

6 - google+:

7 - E-mails: