Bits4Bots - Simple Touch Switch 3904 NPN

Hello :)

This project will show you how to make a simple touch switch using a 2N3904 (NPN) transistor.

A newbie special 10 minutes project!

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1. 1 LED
2. 1 2N3904 Transistor
3. Jumper Wires
4. 2 680 Ohm Resistors *or 1K or less
5. Breadboard or PCB w/solder
6. 5V Power Supply

• Place the 2N3904 transistor on the breadboard with the flat side facing you.
• Connect a resistor from the right >>>>> most pin of the 2N3904 to the (+) short leg of the LED.
• Connect the (-) long leg of the LED to ground.
• Place a jumper wire in a spare slot where you placed your resistor.
• Connect the 2nd resistor to the left <<<<< most 2N3904 pin, power (5V) the other end of the resistor.
• Place a jumper wire in a spare slot where the left most <<<< pin of the 2N3904 is connected.

Now that all the parts are connected test the circuit by simply tapping the wires together.

Did it work? YAY!!! Now try touching a wire with your left hand and touching the other wire with your right hand.

You can even have a friend join in, just hold hands and complete the circuit. The current travels through your body completing the circuit and lites the LED. Cool huh?

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Bits4Bots