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How To Use A Transistor

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Transistors are helpful components. They serve the purpose of switching a “high” (usually up to 20V, which won’t shock you) voltage on and off with a much smaller voltage of 1V (less than an AA battery) or more. If you’ve wondered how to use a transistor in a circuit, finish reading this guide to find out how!

How to Use a Transistor
Image Credit: By Aminba1376 – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=53191778

To make the circuit, you need just a couple of things, shown in the list below.


Let’s start with the schematic (circuit diagram), which I made in Tinkercad, an online CAD program. Here it is:

This image has an empty alt attribute; its file name is Screenshot-2021-12-17-8.14.59-PM-1000x520.png

When you click the button, electricity from the coin battery goes into the middle (base) pin, which changes the conductivity of the transistor, resulting in the left and right side (collector and emitter) pin connecting, powering the LED with the 4 AA battery pack.

To build the circuit, first set out the components. Push the transistor into the breadboard. Also, push in the LED or another actuator. After that, find your LED/actuator power supply and your trigger power supply. Next, hook the LED power supply into the power bars on either side of the breadboard, and lay the trigger power supply out beside the breadboard.

Next, as in the schematic, use a jumper wire to connect one leg of the LED to the row on the power bar with a minus sign next to it. Connect the other leg to the transistor pin on the far right.

After that, connect the Collector pin of the transistor (on the far left) to the power bar marked with a plus sign. Also, connect the negative wire of the trigger power supply to the power bar with a minus sign. If you can’t figure out what wire is positive and which is negative, don’t worry about that until later. Lastly, connect the positive wire of the battery to the Base (middle) pin of the transistor.

That’s all! If it doesn’t work, try flipping the LED around, so that the pins are reversed. If it still doesn’t work, try flipping around the transistor. You could also try reversing the LED’s power supply or the trigger power supply. You can easily adapt this circuit to work with other actuators, triggers, and power supplies. The transistor will work as long as the power voltage is less than 20V. To get that voltage, you would need about 15 AA batteries, so it’s not likely that would happen! The trigger voltage can be anything from 1V to 10V. Thank you for reading, and have fun!

John H (7)


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