Touch switch circuit using Transistor

touch switch circuit

There is a list of touch switch circuits some are complicated and some are very simple. In this article we are going to build some simple touch switch circuits. We will use  basic components( transistor  and popular IC like 555 timer, 4011 CMOS, flip-flop IC).

We can control our scandery circuits by using these touch switch circuits. For example we want to control our bulb with touch circuits then we will use relay with touch circuits.

This article consists of 7 circuits with circuits diagrams. You can choose according to your desires.

Touch switch circuit using Transistors

This is very simple circuit which turns on LED by touching finger. This circuit is very basic circuit for beginners. This simple circuit consists of few components. Step by Step instruction of building of this circuit is given in the circuit diagram given below.

Circuit Diagram


Basic purpose of this project is to trigger an LED with a simple touch. Skins resistance is about 600K to 1M. So if we try to build a circuit using just an LED, power supply and touch conductors, the LED will not glow because, skin’s resistance is very high that prevents enough current. So we have only option is to amplify the tiny current flowing through the skin to a magnitude enough for an LED. For amplify the current, we have to use transistors. The circuit will also work with just one transistor, but the LED doesn’t glow bright with single transistor. That is way we are presenting two circuits diagram 1 with single transistor and 1 with two transistor

Tiny current flows through the skin when touch conductor is touched by finger. This tiny current is amplified in magnitude by the transistor and enough current flows through emitter to collector and LED glows.

Components Required:

  • BC547 (or any other npn transistors)
  • Resistors: 1K
  • LED
  • 9V Power Supply

touch switch circuit