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Author Topic: PWM motor control
Mr.What
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Posts: 154
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Post PWM motor control
on: January 7, 2012, 15:51
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I am looking into doing a PWM motor speed control from an Arduino output. I had something like this in mind.
Image
I might be drawing .5 to 1 A, (12v).

  • How might I identify an appropriate power switching NPN transistor, if I salvage one.
  • I think that an N-channel MOSFET would be the "modern" equivalent of an NPN power BJT. Is this correct? If so... how might I identify one of these for salvage.

For either case, I want to be able to toggle off/on state with a voltage of less than 3v, or small current from the base/gate to the "ground" side of the transistor. (Low side switching?) The voltage at the high side of the transistor is greater than my logic level, so I can't use PNP, or P-channel? MOSFET.
adric
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Posts: 162
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Post Re: PWM motor control
on: January 8, 2012, 15:23
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based on previous projects ive done like that, id probably suggest the TIP120 power switching transistor. nice thing about them is they can be heat synced and they can handle a pretty heavy load. (more than your doing here)

This instructable has an example as good or better than i could supply. http://www.instructables.com/id/Use-Arduino-with-TIP120-transistor-to-control-moto/

finding them in something used is not too hard either. ups's/power supplies. all often use them.

-Quelab, Come make something!

Mr.What
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Posts: 154
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Post Re: PWM motor control
on: February 1, 2012, 16:31
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The power resistor heats up. Unfortunately, the heat sink is on the collector, so it is not at ground voltage. I need to find a good way to keep it cool. Since I'm controlling a fan, it would be nice to put it somewhere around the fan airflow. Any suggestions on how to make a small fan assembly (and connector) that puts the transistor near the fan for heat dissipation?
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