Activity- Two Finger Touch Sensor

The purpose of this project is to trigger/switch an LED with a simple touch. The skins resistance is about 600K-1M. So, if you try building a circuit with just an LED, power supply and touch conductors, the LED doesn’t glow. This is because, high skin’s resistance prevents enough current to flow through the circuit. So, the only option we have is to amplify the tiny current flowing through the skin to a magnitude enough for an LED to glow. For that purpose, we have to use transistors.

Components required –

  • Battery

  • Breadboard

  • LED

  • Resistor – 470 ohm

  • BC547 Transistor

  • Connecting Wires

Circuit Diagram:

This is the circuit diagram for Finger touch sensor.  The second figure is of pin configuration of transistor. This diagram will help you in connection of components more easily.

 Steps to follow:

Step 1: Open Tinkercad, click on ‘Create new circuit’.

Step 2: Connect battery to the breadboard as shown.

Step 3: Take out NPN Transistor and place it on the breadboard as shown.

Sep 4: Take out a LED and place it on the breadboard as shown.

Step 5: Now take a resistor and place between collector of transistor and short lead of LED ass shown.

Step 6: Connect emitter to the ground rail.

Step 7: Connect long lead to the positive rail.

Hence the circuit is ready. Now touch the two wires and LED will start to glow.