Foot Pedal Adaptation

[BobW]

Wrong way round, it's directly proportional, so will go massively high when it goes OC

Yes, of course, you're right. I've been getting everything backwards lately.
Still, the pedal could be inserted where the 7.5k resistor goes, along with suitable adjustment to the other components. I'm assuming the OP wants the speed to increase as the pedal is depressed.

 

[Nigel Goodwin]

Yes, of course, you're right. I've been getting everything backwards lately.
Still, the pedal could be inserted where the 7.5k resistor goes, along with suitable adjustment to the other components. I'm assuming the OP wants the speed to increase as the pedal is depressed.

It's be very confusing if it didn't

But because it's not a pot, and indeed not just a variable resistor, it's not really suitable for what he's trying to do.

I suggest he buys a proper one:

Foot Pedal Potentiometer - Sewing Machine Speed Controller

We've had a foot pedal switch in the store for a while but some people have contacted us asking if there was a way to retrofit it to perform variable speed control, like a potentiometer. ...

www.adafruit.com

Or how about getting the throttle pot from a modern car?.

 

[LukeKnepp]

Okay, so I looked at that foot pedal, and just wondering, do I put whatever size pot in there that I want?

It looks like it comes with a 20k installed...

 

[Nigel Goodwin]

Okay, so I looked at that foot pedal, and just wondering, do I put whatever size pot in there that I want?

It looks like it comes with a 20k installed...

It depends if you can change it or not - otherwise adapt the top resistor to compensate.

As I said previously, you need a resistor in series with the pot, which sets the maximum output voltage, and increasing the pot value decreases the output voltage. You could also add a resistor in parallel with the pot, to decrease it's maximum resistance.

What voltage range are you looking for?.

 

[LukeKnepp]

What voltage range are you looking for?.

I am looking for 27 volts down to as near zero as possible...