A transistor, a resistor and an LED.
See the video below to see how I connected it. Or skip the video if you prefer to read how to connect it.
Connect the resistor and LED in series from the positive supply to the collector of the transistor. Choose a resistor that sets the current of your LED to around 20 mA.
Connect the emitter of the transistor to the negative terminal of the supply.
Now, create two wires with exposed ends – so you can see the metal.
One goes to the positive supply. The other goes to the base of the transistor.
This is all it takes.
Now, try to touch these two wires with your finger – and the LED lights up!
The reason is that your finger acts as a resistor and will give enough current to the base of the transistor to turn it on.
This is one of the circuits you will build in «Getting Started With Electronics». Along with other fun and simple circuits, to get you started in electronics. Get it here:
Keep on Soldering!
Oyvind
Copyright Build Electronic Circuits
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