Non-Contact Voltage Detector by using transistor

non connact ac test

Non-Contact Voltage Detector: Electricity can cause injury or even can become the cause of death that is why safety must come first when working with electrical devices or electricity. In this article, we will show you how to design a simple efficient Non-Contact Voltage detector by using transistors.  You can build this circuit by using simple components and test the presence of AC voltages. You need not worry about getting zapped because it is a non contact voltage tester.

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non connact ac test

In this modern age almost everything we use with an electric current. Before working with AC object we must verify that the current is not a presence where we work. So we use the tester, A non-contact voltage tester is a safe way to make sure that the AC power is off.

In this project, we have designed a very simple Non-Contact Voltage Tester Circuit by using transistors. we have used only one type of transistor in this project.

Circuit diagram Non-Contact Voltage Detector


Components Required For Non-Contact Current Tester

Qty. Part Description Mfr. Part No.
3 Transistors BC547 (NPN)
1 LED, Red or any color
1 Buzzer (optional) 3v
1 Switch any type
1 9V Battery or 3v can be used also  or supply
1 Battery Snap
1 Case any plastic cover plastic cover

Required Tools:
Soldering Iron
Drill and drill bits (for making holes in the box)
Copper Wire
Cutters (for copper wire)
Adhesive Tape

Circuit Design of Non-Contact Voltage Tester

Make an antenna with a small piece of copper wire and is connected to the base of the first Transistor (BC547). Antenna detects the magnetic field when we placed it near AC objects like cables and switches and etc, it gets a small amount of current and activates the first transistor through the base.

The output of the first transistor drives the second transistor, it gets activated and the third transistor activated with 2nd transistors output. As the third transistor activates, the LED is turned ON.

We can use a small buzzer on the place of LED. The buzzer will alert you through voice, Buzzer should 3 volts because we are using 3v battery.

How to Operate non-contact-voltage-detector?

  • Make the connections as per the circuit diagram.
  • Connect the battery to the circuit.
  • You can place the circuit in a small box.
  • Place the antenna near to the electrical appliances.
  • LED will run if the voltages are passing through the objects.

Applications of non  contact-voltage-detector

  • This simple Tester can be used in many places and near many objects like switches, cables, outlets, cords, junction boxes, circuit breakers, fans, motors, etc.
  • you can make it portable by fixing it into a small box.

Two Transistors  voltage tester

Thank you so much for visiting our website if you have any question about this circuit or any circuit about electricity or electrons you can discuss freely.

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