This is an easy circuit for Simple ON-OFF Touch Switch Circuit with Relay, where we touch one time and it turn ON and touch again it will turn OFF.
Furthermore, this circuit is good to control light, fan or other electronic device, where there is no need of expensive or hard parts, also there is no need of push button just a touch only!
What is a ON-OFF Touch Switch Circuit with Relay:
With relay help ON-OFF touch switch circuit can control device or load by just touching small pad, when we touch the circuit feels it and relay turn load ON or OFF.
Also, use this type of circuit when we do not need normal buttons, like in touch control systems or smart devices.
Circuit Working:
Hence, if someone want to turn ON/OFF 220V device then it must use this circuit with relay and the 220V power and load must connect correct with relay pins.
Parts list:
| Components | Values | Quantity |
|---|---|---|
| Resistors (All resistors are 1/4 watt) | 1M CFR | 2 |
| 330Ω CFR | 1 | |
| Capacitors | 0.01μF | 1 |
| Semiconductors | IC 555 | 1 |
| LED 5mm 20mA | 1 | |
| Copper Touch Pads | 4 | |
| Relay 6V to 9V | 1 | |
| Diode 1N4007 | 1 |
When we do not touch the circuit, the 555 IC stays stable, it can be ON or OFF and when we touch the ON copper strip, a small negative signal from our skin goes to the trigger pin.
This signal make inside part of IC (comparator and flip flop) and changes to ON state, so output become HIGH (ON).
But when we touch OFF copper strip small positive signal goes to threshold pin and then inside comparator send signal to reset pin and this make output go LOW (OFF).
Formulas:
Here, is formula for Simple ON OFF Touch Switch Circuit with Relay:
To find voltage at sensor (Vsensor) when touch uses this formula:
Vsensor = Vin × (Rtouch / (Rpullup + Rtouch))
where:
- Vin is power supply voltage of circuit.
- Rtouch is sensor resistance when finger touches we can see in datasheet.
- Rpullup is value of pull-up resistor.
How to Build:
To build a Simple ON OFF Touch Switch Circuit with Relay follow the below steps:
- Before putting the 555 IC on PCB check small dot or notch on IC match with PCB or breadboard notch.
- Now, connect power like positive wire to (+) rail and negative wire to (–) rail on PCB.
- Then, connect pin 8 of 555 IC to (+) supply.
- After that, connect pin 4 to pin 8.
- Next, join pin 5 to pin 8.
- After that, connect pin 2 to touch plate for ON.
- Then, connect pin 6 to touch plate for OFF.
- Next, join pin 7 to pin 6.
- Then, connect pin 3 to output like LED or Relay.
- And, connect pin 1 to ( –) supply.
- Also, use 4 copper plates for touch.
- First two plates for ON and place very close with 2mm gap.
- Then, connect both to (–) supply.
- Next, two plates for OFF and also should be close.
- Connect both to (+) supply.
- If using LED put resistor in series before LED.
- Also, connect other side of LED to pin 3.
- And if using relay connect relay coil between pin 3 and (+) supply.
- To control any outside device use relay contacts.
- Now give power to circuit.
- To test touch ON plates LED or relay will turn ON.
- Touch OFF plates LED or relay will turn OFF.
Conclusion:
This Simple ON-OFF Touch Switch Circuit with Relay help anyone to control device easily with just by one touch.
Also, this project uses 555 IC which is simple and adjustable and so it makes circuit safe and flexible.
Try new idea and make fun project and see how touch control circuit make things easy!