In this tutorial, we are making a project of a Simple touch switch circuit. It is used to activate a relay instead of an LED and resistor so that you can connect your desired load or electronic appliance with it and operate it through this circuit. This circuit is very sensitive because we have used two transistors that are working as a Darlington pair.
Hardware Components
The following components are required to make the Touch Switch Circuit
| S.no | Component | Value | Quantity |
|---|---|---|---|
| 1. | Battery | 6V | 1 |
| 2. | Transistor | 2N2222 | 2 |
| 3. | Resistor | 330Ω | 1 |
| 4. | LED | – | 1 |
| 5. | Variable Resistor | 200K | 1 |
2N2222 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 2N2222
Touch Switch Circuit
Working Explanation
Two transistors are used as a Darlington pair. The first transistor is amplifying the gain first and then it is further amplified and multiplied by the second transistor so as a result, we get a very high gain. Because of this high gain, the circuit is sensitive to even a very small amount of current passing through our skin and activates the LED. This circuit can be operated on either 6,9, or 12 volts. When using 6V use 330Ω in the place of Rx, while using 9V or 12V use 390Ω or 470Ω resistor respectively. If you are planning on using a relay at the place of Led and resistor then use the relay of the same value as the input voltage. A 200KΩ variable resistor is used to adjust the sensitivity of the circuit.
When you touch the touchpoints of the circuit a very small current starts passing through our skin which completes the circuit due to which both the transistors (Darlington pair) activate and the LED lights up.
Applications and uses
- Locks
- Safety boxes
- Lamps
- Doors
