To repair electrical devices, the master often needs a device that will ring the circuit and ensure that it is intact. The tester can be light, sound and combined. The principle of operation is simple – when two probes are closed, the device gives a signal about the integrity of the connection. Such devices are commercially available, but the simplicity of their design allows you to assemble a simple circuit yourself.


Materials and tools needed

Any home master will make such a tester, spending only a few tens of minutes. It consists of the simplest parts that are easy to find without going to a radio parts store:

  • Wooden or hard plastic base 8×8 cm;
  • Small bar 1×2 cm;
  • Kron Battery – 9V;
  • crown connector;
  • Switch of any type, with position fixing;
  • Two connection terminals for wires;
  • Yarns of different core stiffness;
  • LEDs of any color for a voltage of 2 – 3 V;
  • Buzzer for voltage 3 – 12 V;
  • Fixed resistance of 1 kΩ.

If there is no connector for the tester power supply, you can take it from the old Krona. The battery is dismantled and the contact part is disconnected from it. It is only important to take into account during installation that the old “minus” will become a “plus”, and vice versa.

Of the tools, you only need a soldering iron with solder and flux, as well as a loaded glue gun. It will be easier to fix the parts on the site with such glue, but if it is not available, you can use another suitable analogue.

assembly instructions

Installation of a homemade tester begins with gluing the connector. In order for the connector to be correctly positioned on the site, it must be glued to a wooden bar, and then fixed on the base.

In addition, at the edge it is necessary to place the switch and the connection terminals. They are installed in such a way that in the future it was convenient to use them.


Now we need to add the main components – the indicators – to the diagram. The buzzer and the LED are connected in parallel, respecting the polarity.


But you need to add a resistor to one of the LED contacts – without it the part will turn off instantly. To the connections of the buzzer contacts, you need to solder a wire to the “plus” and “minus”. The parts are attached with hot glue in the center of the device platform. It is important to drown the resistor and all metal contacts in silicone.

Next, the negative wire of the buzzer must be soldered to the negative of the Krona connector. And pinch the second output into one of the terminals. The plus of the power goes to the second terminal via the switch.


The device itself is already ready, but you cannot do without wires with probes to use it.

Important! All bare contacts on the site must be insulated – they can be drowned in hot glue.

Probes for the tester can be made independently of thick section copper wire.

For convenience, they should be at least 5 cm long, while the bare working part can be up to 2 cm. It is better to choose soft, stranded probe wires, about 30 cm long and shrinkable with heat shrink.

If the polarity was correctly observed during assembly and all parts are in good condition, the continuity tester can be used. The device will become a faithful assistant while working with an electrician. But it should be borne in mind that the device is designed only to monitor connections – by applying voltage to the probes, parts can fail.