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How does one choose the right 100k potentiometer? Answered

I am building a pickup winder... a simple machine that winds hair-thin copper wire around magnetic poles.

I need to build a 12V DC geared electric motor speed controller.

I bought the following...

  • 12V DC 1000RPM geared electric motor
  • LCD punch digital counter with a magnetic proximity switch
  • 12V Double-Pole Double-Throw (DPDT) ON/OFF/ON toggle switch
  • DC12V 2A Power Supply Adapter: AC100-240V to DC12V

I know that a DC motor controller can be purchased for around $5-10, but since I am brand n00b to electronics, I want to take the opportunity to learn as much as I can by building everything (or as much as makes sense) myself. I found this Instrucable on building a DC motor speed controller. It seems simple enough, however, when I go to the Digi-Key website and look for 100k Ohm pots... there are a lot to choose from.
I do not care about form factor. I have no size restraints or aesthetics. I just need a knob... that I can turn... that will allow me to set it to zero, switch the machine on and have the motor not turn at all... then slowly begin to spin as I turn the knob up to 10, and it is spinning at its top speed (1,000 rpm).

This is the motor, this is the power supply, this is the counter, and this is the switch that I bought for this project.

According to the instructable referenced above, I need: an IRF3205 mosfet, a 100k ohm potentiometer, and a heatsink. I do not yet have the vocabulary to even properly Google "How to tell which 100k ohm potentiometer works with a 12V DC motor..." Can someone please point me in the right direction?



10 months ago

You want these:

Basically, a 100K linear pot (denoted by the B marking). This adjusts the increase in resistance linearly, as opposed to logarithmically (which has an A marking, and it better for volume knobs).

Have you considered using an old record player to spin the pickup? That way, you know precisely how many rotations the record player is making a minute, and you can time / measure rotations very precisely. I've seen a lot of guitar pickup winders built this way.


10 months ago

It does not matter, only the value in Ohm matters.
You are not dealing with the power here, the potentiometer only provides a value for the electronics at a very low current level.
So pick whatever potentiometer has the right prices, sizes and looks as long as the resistance in Ohm is what you need. ;)