# What size potentiometer?



## Fewski (Jun 27, 2012)

I'm not sure how the sizes for potentiometers are calculated.. so need some help here.

I'm building a controller to run a 500 Watt 36 Volt motor 18.3 Amps. I have no idea what size potentiometer I need to do this. Any help on calculations?

Thanks


----------



## major (Apr 4, 2008)

Fewski said:


> I'm not sure how the sizes for potentiometers are calculated.. so need some help here.
> 
> I'm building a controller to run a 500 Watt 36 Volt motor 18.3 Amps. I have no idea what size potentiometer I need to do this. Any help on calculations?
> 
> Thanks


The pot is used as a control input signal from the throttle pedal or twist grip. It normally runs 0 to 5 volts or maybe 10V max. Typically it is a 5 or 10 kΩ pot.


----------



## Fewski (Jun 27, 2012)

Thanks for the reply. What about the amount of Ohm's? I've seen them from 50k to over 1m.


----------



## frodus (Apr 12, 2008)

major said:


> Typically it is a 5 or 10 kΩ pot.


He already told you.

If you're building this and are asking how many OHM's, I'm a bit worried. You can choose how many ohms you want to use. How the controller uses the signal into the microcontroller that is signalling the FET's is up to you and your design.

Normally people have 5V attached to one end of the pot, signal ground to the other end, and the wiper goes to the A-D converter (with some filtering for noise). That way the A-D converter sees a voltage between 0 and 5V. How many ohms you use is completely up to you, but normally we see 5-10kohm potentiometers.


----------

