Transistor Touch Switch

Hello everybody! Today, I'm going to show you how to make a transistor-amplified touch switch. Let's get right in to the build!

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Step 1: Part

For the switch, you will need:

  1. Piezo Buzzer (1)
  2. LED (1)
  3. 100K resistor (1)
  4. 220 ohm resistor (1)
  5. NPN Transistor (2)
  6. Jumpers (several)
  7. Breadboard
  8. 5-6v battery pack

Step 2: Circuitry

This circuit is very simple. I left a bunch of notes on the images to help with assembly to help supplement the directions. Anyway, let's build the circuit!

  1. Wire the emitter of the transistor to the base of the second.
  2. Now connect the emitter of the second transistor to the negative power bus of your breadboard.
  3. Bridge the collector of the first transistor to the positive power bus.
  4. Now connect the cathode of the LED to the collector of the second transistor with your 220 ohm resistor.
  5. Insert a jumper in to the positive power bus of your breadboard.
  6. Afterwards, connect another jumper to the base of your first transistor.
  7. Now connect the positive lead of your Piezo buzzer to the positive power bus.
  8. Connect the negative lead of the Piezo in parallel with the cathode of the LED.

That's it for the circuit. Power up your breadboard and you will have a functioning touch switch. All you have to do is bridge the gap between the two "free" jumpers with your finger and, Ouila, your buzzer will sound and the LED with light up. Thanks for reading, and, as always, Happy Making!

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    1 year ago

    I made the circuit on a breadboard first to make sure I had it working correctly. Then I put it together permanently and it works! Your pictures look like they are upside down. You might want to fix them. Thanks for the tutorial.