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I would like to use a transistor in my circuit to cut off power. My power supply gives out 12v @15 amps. I think in this case I’ll use a npn transistor. Which kind of transistor can sustain this amount of power? I will be using this circuit to power up a motor. Just for understanding the npn transistor a little more, the positive wire from the power supply is connected to the “collector” of the transistor, and the positive wire of the motor is connected to the “emitter” of the transistor, while the negative of the power supply is directly connected to the negative of the motor. Then the “base” of the transistor is connected to one of the analog pins of the arduino. I am not completely sure of this please correct me if i’m wrong. Thanks a lot Mitch

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At that amp rating (15amps) the NPN Transistor wouldn’t be a good idea

It would be better to use a relay to switch the power. Something like this

https://www.amazon.co.uk/Single-Channel-Level-Trigger-Module/dp/B00GWFDNT2/ref=sr\_1\_6?ie=UTF8&qid=1469652074&sr=8-6&keywords=single+channel+relay+mains

The above relay will switch 10amps of mains voltage AC 250V/125V given a high/low 5v DC voltage

This link gives some good information and methods for switching a 3D printer off

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Thank you so much this was really helpful, will try it out! :slight_smile:

thanks again mitch