A human touch can do magic!
So this Simple Human Touch Sensor Circuit with Transistor shows how a tiny finger touch can switch ON a light; therefore, no switch, no button just a skin current makes it work.
Also, it is a cool and educational mini project for learners.
Circuit Working:
Parts List:
| Components | Values | Quantity |
|---|---|---|
| Resistor | 470Ω 1/4 watt | 1 |
| Semiconductors | Transistor BC547 NPN | 1 |
| LED red or any color | 1 | |
| Battery 9V | 1 | |
| Touch Probe Metal wire or plate | 2 |
When we touch both metal points our finger provides small current then this small current goes to the base of the transistor BC547 and then the transistor becomes ON.
Now current flows from battery through LED and resistor and then LED glows.
When we remove or finger the base current stops and then transistor becomes OFF and also 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
- First, gather all the components as shown in circuit diagram.
- Next, emitter pin goes to negative of 9V battery.
- Then collector pin connects to one end of resistor R1 and other end of resistor connects to LED cathode.
- After that, LED anode goes to 9V battery positive.
- Also, base of transistor connects to the one side of touch plate and other side of touch plate connects to battery positive.
Conclusion:
To conclude, this project is for Simple Human Touch Sensor Circuit with Transistor, it works with body current and it also shows basic transistor switching action.
Furthermore, this project is good for students and beginners in electronics.