Simple Human Touch Sensor Circuit with Transistor

A human touch can do magic!

This Simple Human Touch Sensor Circuit with Transistor shows how a tiny finger touch can switch ON a light.

No switch, no button just a skin current makes it work.

It is a cool and educational mini project for learners.

Circuit Working:

Parts List:

When we touch both metal points our finger provides small current.

This small current goes to the base of the transistor BC547.

The transistor becomes ON.

Now current flows from battery through LED and resistor.

LED glows.

When we remove or finger the base current stops.

Transistor becomes OFF.

And LED turns OFF.

Formulas with Calculations:

Below is the formula with calculation for Simple Human Touch Sensor Circuit with Transistor.

Transistor current gain formula is:

Ic = β × Ib

If LED current (Ic) = 10mA

and transistor gain (β) = 100

then base current (Ib) = Ic / β = 10mA / 100 = 0.1mA

This small base current comes from our body when we touch.

Resistor R1 controls LED current.

LED voltage drop = 2V (approx)

Battery = 9V

Voltage across resistor = 9 – 2 = 7V

R = V / I = 7 / 0.015 = 466 ohm = 470 ohm used.

How to Build:

To build a Simple Human Touch Sensor Circuit using Transistor

• Gather all the components as shown in circuit diagram.
• BC547 transistor has 3 pins: Collector, Base and Emitter.
• Emitter pin goes to negative of 9V battery.
• Collector pin connects to one end of resistor R1.
• Other end of resistor connects to LED cathode.
• LED anode goes to 9V battery positive.
• Base of transistor connects to the one side of touch plate.
• Other side of touch plate connects to battery positive.

Conclusion:

This project is for Simple Human Touch Sensor Circuit with Transistor.

It works with body current.

It shows basic transistor switching action.

Good for students and beginners in electronics.

References:

saw an interesting touch-effect using resistor and transistor!