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Thread: Transistor/Fan Circuit

  1. #1

    Transistor/Fan Circuit

    Hello. I am trying to build a circuit that controls a 12V fan from the teensy 3.2 using a PN2222A transistor. My goal is to eventually control fan speed using pwm. For now the teensy is simply outputting 3.3V. I have run the circuit in multisim with a 12V lamp and the system worked. I have also got the system to work using an Arduino's pwm output to the base of the transistor. Whenever I use the teensy, however, it fails for some reason and the fan does not run. I have attached below the schematic (which is from multisim and contains a 12V lamp instead of a fan), a photo of my breadboard, and a photo of my code. I know the fan works because when it runs when I directly attach it to 12V. The transistor datasheet can be found here. If anyone has any suggestions please let me know.

    Schematic
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    Breadboard
    Click image for larger version. 

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    Note that while it's not pictured the main power supply is supplying the power rail of the breadboard with 12 VDC.

    Code
    Click image for larger version. 

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  2. #2
    Senior Member PaulStoffregen's Avatar
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    Looks like this should work.

    Maybe there's a mistake or misunderstanding in wiring. I can't see it well enough.

    Can you show a large version of the image, ideally with the camera zoomed in to the circuitry?

  3. #3
    Senior Member
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    As Paul says, the photo is not clear enough to be sure of the connections. But the short red wire seems to connect the emitter of the 2N2222A to +12V instead of to ground.

    Pete

  4. #4
    Hi guys. Thanks for the responses. Turns out the transistor I was using was faulty. Once I changed it out with a fresh one the system started working. Thanks!

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