In this tutorial, we are going to make a “Simple Touch Switch Circuit”.
As human beings, we try to make things easy simple touch switch is one of them. We want certain actions to be done with only a touch instead of pressing buttons. To Sense the touch event, we don’t need complex circuits or microcontrollers, we can sense the touch by using a simple touch switch circuit using a timer IC 555. This simple circuit contains a few easily available components, you can use any conductive material as a touch switch be sure to place these two plates near each other. If you need to ON or OFF the appliances with a touch then you can refer to this circuit, this circuit senses the event and makes the output LED glow and it remains in the glow for a few seconds and then becomes off condition. This switch doesn’t need direct contact with metal and therefore eliminated the security risks, it gives a sleeker view to the devices like UPSs, and Mixer-grinder.
Hardware Required
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Touch Plate (refer to text) | – | 1 |
| 2. | IC | NE555 Timer | 1 |
| 3. | Resistor | 100K, 470Ω | 1, 1 |
| 4. | Capacitor | 10uF/25V, 0.01uF | 1, 1 |
| 5 | LED | – | 1 |
| 6. | Connecting Wires | – | 1 |
| 7. | Power Source (Battery or Regulated power supply source) | DC 6V | 1 |
Circuit Diagram
Working Explanation
In this circuit timer, IC 555 is acted as a monostable vibrator, so the trigger pin is connected to a touch plate, and another touch plate is connected to the ground supply. The voltage supplied in this circuit should be 6V, doing so will result in IC burnout. The capacitor between pin6 and pin1 C1 (long or short duration pulse at output one can get by changing its value) determines the turn-on time of the LED once a trigger is passed. So, with the capacitance change, one can get many turns on time.
When the power is turned ON, the LED will not turn on as long as the trigger is not given. The trigger pin in the timer is a high impedance one and is very sensitive, it can merely be pulled high by human body potential. This trigger determines the output of the 555 and SETS the flip-flop inside the 555 timers. When this pin is high the output will be high and when this pin is low the output is low. This pin is very sensitive to touch and it will pull the 555-output high when a touch occurs. Here at the touch, the trigger pin forces the flip-flop to SET mode and so the output goes high. However, this high stage can’t be retained for long once the trigger is removed. Once the touch is removed the high stage of output merely depends on the charging time of the capacitor connected between pin6 and pin1. The capacitor once reaches a voltage level discharges through the THRESHOLD pin (pin6) of 555. On capacitor discharge, the threshold pin goes high resetting the flip-flop which is set HIGH by the trigger pin and so the output also goes low with it. Hence the LED turns off at capacitor discharge. This means when the finger touches the plates the trigger pin receives a low trigger signal and then the timer will produce a mono pulse at the output pin.
Applications
Touch switches can be used in places like dusty or wet areas, where normal switches would not last long.
- It can be used in touch-based blinking lights.
- It can be used to detect the electrostatic build-up in a room.
- Touch switches for doorbells.
- It can be used to make touch-based buzzers.
