Despite the abundance of measuring equipment, I always use a simple homemade tester made from a ballpoint pen. It allows you to instantly find out the polarity of a unit, battery, source, etc. Does not require power and is always ready to work. Auto electricians will also need this essential item in their household.
For those who are interested in logic when building circuits on Arduino, this device will be useful and will be extremely convenient for monitoring states on the board.
It is necessary to make a probe from a piece of copper wire. To do this, it is sharpened on one side and tinned on the other.
LEDs soldered to each other counter-parallel.
We bite off one contact at a time with wire cutters.
Solder the probe.
We solder a line of resistors connected in series.
Drill a hole in the pen cap for the wire.
We insert the wire into the cap and solder it to the resistors.
We install the circuit in the handle. One nuance emerged: LEDs did not fit further into the middle of the body. I had to unsolder the probe and solder the extension wire.
Solder the probe again. We fix it with a cap.
We solder an alligator clip to the second end of the wire.
To make the tester mobile, we will make the wire spiral. To do this, we wind it onto a larger diameter and blow it with a hairdryer to fix the shape.
The tester is ready!
It works very simply: If there is a plus on the sharp probe, then the green light is on Light-emitting diode.
If it's the other way around, the light is red.
Everything is very simple, fast and convenient.
The tester operates free of voltage of 2-25 V. Indicates the presence of voltage and its polarity. If it is variable, then both will light up LED.
It can also be used in conjunction with a battery for testing diodes and LEDs.
