It will be very cool if you make this mini tester and always carry it with you in the car. After all, with the help of it you can: check the functionality of lamps and fuses without removing them from their seats, find out the polarity and presence of voltage in the conductor without even removing the insulation from it, check any circuit for a short circuit and much more. A very necessary thing that can be useful not only in the car, but anywhere.
Will need
- Two LED different color.
- Two resistors of 200 Ohm and 1 kOhm.
- 3 V coin cell battery with connector.
- A piece of wire.
- Alligator clip.
- Small plastic case.
Battery with block:
Plastic case from an old telephone headset:
Tester circuit
The scheme includes two LED back-to-back parallel with each other, with which the battery is connected in series. As a result, when two contacts are closed, green lights up Light-emitting diode, and when connecting power from outside, the red light is on Light-emitting diode. Below you will see how all this can be useful.
Manufacturing
So, we install the battery in the block. Next, glue it into the body using hot glue.
In the window from under the button we insert two LED and solder it according to the diagram.
Add resistors.
To make a probe, take a medical syringe needle with a wide hole so that the resistor leg fits into it.
We bite off the stem from any unnecessary resistor and insert it into the opposite direction of the needle. We fix everything with hot glue. The resistor contact should stick out.
Solder the probe to the tester.
We solder a small wire to the second contact of the battery and check the operation.
Fill all the voids with hot glue.
Close the back cover and you can use it. We fasten the clamp to the wiring.
How to use?
The tester is already ready for use; to “ring” something, insert an object between its probe and clamp. And if, say, the fuse is good, the green LED will light up.
To check the presence of power, connect the clamp to the common wire and use a probe to check the source. If there is a “+” there, the red light will turn on.
And if it’s a minus, then it’s green.
The needle pierces the wires perfectly and does not need to be stripped.
To take the tester with you, put a protective cap on the probe needle and take it with you for your health, it will not run out of charge and will always be ready for work.
