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I have followed this tutorial:

http://www.instructables.com/id/Automatically-water-your-small-indoor-plant-using-/?ALLSTEPS

Every time i try to run my circuit, My transistor gets very hot and breaks.

I have exactly the same parts as the tutorial. I have also tested the circuit with 3.3V Power supply and a diode instead of an engine, this works.

I am super thankfull for any answers.

  • What do you mean by "breaks?" Can you please add more information to your post? Thanks! – Anonymous Penguin Nov 25 '14 at 23:03
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    I would be surprised if it worked. As far as I can tell (from the poor instructions) he is connecting the base directly to the Arduino pin. This would overload the chip, although the inbuilt current limiter would protect it. I certainly wouldn't use a PN2222 to switch 300mA. – Milliways Nov 26 '14 at 5:16
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    As @Milliways suggested, you need to add a resistor between the arduino pin and the transistor. Around 1k will do. – Gerben Nov 26 '14 at 16:43
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Measure the Current through the motor, the PN2222 can pass a maximum of 600mA. I would guess that just over half an amp would be enough for the motor but you can check what you motor is trying to pull by connecting it to 12 V direct and measure the supply current. The only thing that will make the transistor hot is excess current

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