Touch Switch Circuit

ON-OFF Touch Switch Circuit Using MOSFET.

This is An Effective, Easy, Simple, And Very interesting Circuit. Only One MOSFET and One Relay is Used in this Project.

Use 9v DC Supply Voltage to the circuit.

When we touch on the Ground and Gate terminal, then the Appliance is Switched OFF. And When We touch on The Gate and Supply, then the Appliance is Switched ON.

Touch Plate Made of Two Plates Separated by a Small Gap.

Introduction to MOSFET

MOSFET stands for a metal-oxide-semiconductor field-effect transistor. It is a special type of field-effect transistor (FET).

BJT is ‘current controlled, ’ and the MOSFET is a voltage-controlled device. The MOSFET has “Gate“, “Drain”, and “Source” terminals instead of a “base”, “collector”, and “emitter” terminals in a bipolar transistor.

By applying a voltage at the Gate, it generates an electrical field and makes conductivity of current flow through its between Drain and Source, and there is no current flow from the gate into the MOSFET.

This touch ON/OFF circuit toggles the state of the relay when the respective touchpad is activated. The relay controls the 230V AC bulb, turning it ON or OFF accordingly.

1. Turning ON the Load (Bulb)

When you touch the “Touch Here to ON” pad, the small capacitance from your finger activates the MOSFET’s Gate (G).
This touch point is made with the wires connected with Gate and Positive supply.
After touch here, A connection is created between the +ve supply and Gate of Mosfet. small +ve supply goes to the Gate pin of Mosfet, and this is charged and activates it and turns it ON.
The MOSFET (IRFZ44N) switches ON, allowing current to flow from Drain (D) to Source (S).
The relay is energized, closing the normally open (NO) contact and supplying 230V AC to the bulb.
The bulb turns ON.

2. Holding the State (Latch Effect)

A capacitor (0.1µF) is connected between Gate (G) and Source (S) to stabilize the MOSFET and prevent false triggering.
The MOSFET remains ON even after the touch is removed.

3. Turning OFF the Load (Bulb)

When you touch the “Touch Here to OFF” pad, the gate voltage of the MOSFET is discharged to ground.
This touch point is made with the wires coming from the Ground(-ve supply) and Gate pin of Mosfet.
When we touch this point, a connection is made between GND and Gate, So The After -ve supply goes to the Gate pin of Mosfet, it discharges quickly and turns off.
This turns the MOSFET OFF, cutting off the current flow through the relay.
The relay deactivates, breaking the connection to 230V AC, turning the bulb OFF.

A Resistor is Required At the Transistor base for limiting the current. But in MOSFET, without resistance at the gate, it can work well. Usually, MOSFET has much Load Power than transistors.

Advantages of This Circuit

✔ No Mechanical Switches – Increases durability and reliability.
✔ Simple & Low-Cost Design – Requires very few components.
✔ Fast Response Time – The touch sensor reacts quickly.
✔ Low Power Consumption – Uses minimal power in standby mode.

IRFZ44N is a Fast Switching Standard MOSFET.

MOSFET AS SWITCH— To use MOSFET as a switch, we have its gate voltage (Vgs) higher than the source. If you connect the gate to the 0v source (Vgs=0), i.e, Ground. Then it is turned off.

Gate Voltage < Source Then OFF

Gate Voltage > Source Then ON

In this Circuit—-

Gate +( +Supply) = ON

Gate + (- Supply) = OFF

Demo Video Of This Project… Don’t Forget To Watch It.

Must Read Remote Control Switch Circuit For ON OFF Light/Fan etc

Very Simple Touch ON And Touch OFF Switch For Appliance. In This Circuit, an N-channel MOSFET IRFZ44N is used as a Switching Element. And a Relay is Connected to Give the supply to the Load Such as Ligh Bulb, Fan Etc

Components

MOSFET IRFZ44N-1

CAPACITOR 0.1UF (104)-1

DIODE 1N4007-1

RELAY 9V 6A-1

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