Hello, the author made such a tool as a tester-dialer from improvised materials.
It took:
LED (color does not matter)
Case from an old felt-tip pen (or something similar)
3 flat batteries (a flashlight from a lighter is ideal).
The author used a solder case. We paint it black, make a hole for the LED and one more for the wire.
We solder one edge of the black wire to the nail and insert it into the ballpoint pen housing, insert the second edge of this wire into the middle of the case through the outlet hole, it is blue connected in the middle (of course the wires can be used in any color, but wires of different colors were used for clarity). We solder the red wire with one end to the second nail and insert it into the lower part of the case, for reliability it can be glued with hot glue.
The second end of the red wire is soldered to the plus of the first battery. We connect the minus of the diode, with the minus of the third battery.
In order for the tool to work correctly, you need to connect the LED correctly, that is, do not confuse the plus and minus. The new diode legs of different sizes longer leg is a plus. Well, if the diode was already in use and its legs are the same size, then we look at the diode itself, and the leg that comes from the larger corner is minus the second leg is certainly a plus. And so where is the plus and minus we figured out. Then we solder the yellow wire to the minus of the diode and the battery, and the plus leg of the diode to the blue wire. Now we connect all three batteries to each other and fix the electrical tape.
Let's check its performance; everything works perfectly. We assemble everything into the case with tweezers, insert the diode into the hole and glue it. Batteries can be replaced at any time by removing the tip.
We check again already assembled.
