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Touch switch circuit using Transistor

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 timers, 4011 CMOS, and flip-flop IC).

Touch switch circuit using Transistor

We can control our secondary circuits by using these touch switch circuits. For example, if we want to control our bulb with touch circuits then we will use a relay with touch circuits. This article consists of 7 circuits with circuit diagrams. You can choose according to your desires.

Touch switch circuit using Transistors

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

Circuit Diagram 

The touch switch circuit using a transistors circuit diagram is given below. You can use any NPN transistor but the pinout detail should remain the same.

Touch switch circuit using Transistors

Working on the Touch Switch circuit

The 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 the skin’s resistance is very high which prevents enough current. So have only option is to amplify the tiny current flowing through the skin to a magnitude enough for an LED. To 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 a single transistor. That is why we are presenting two circuits diagram 1 with a single transistor and 1 with two transistor

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

Components Required for touch switch circuit

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