Setting stepper voltage - double pots?

My i3 kit came with RAMPS v1.4 and stepper motor drivers that have two pots. I've tried searching for setup instructions - or any details - but have drawn a blank. This is quite possibly because I don't now what they are called!

Can anyone help, please? What are they called and where can I find setup instructions, please?

Richard

It would be much easier to identify parts if we knew how they're looking.

your google fu is weak my friend...




(they have removed the image, the rotters)

From [forums.reprap.org]

Edited 2 time(s). Last edit at 05/27/2015 11:00PM by Dust.

What kit is it?

Thank you, Dust, that's it!

I don't know how I missed it with Google. but I did!

Richard

I will take a stab at this. Since I can't see the chip number, it looks like the second pot is used to vary the PWM clock frequency. I deal with this to kill off resonances in motors so they don't sing on VFD's in quiet environments. It may have its purpose here to do that here. The pix says "...to improve accuracy..." but I will step out on this ledge that our movement systems are far more accuracy impeding and this won't amount to a hill of beans.

Addendum: There is a tradeoff here and it's an important one. If the oscillator frequency is turned up to silence a noisy motor, the driver will heat up more because there will be more transitions from on-to-off-to-on in a given unit of time. It is these transitions that heat up the device and the stepper motor, not being on as one would think, as this area is very inefficient and wasteful because of the heat generated. Also, higher oscillator frequencies may lead to less torque availability. And no, there is no cut and dry answer here. One will have to experiment and accept a compromise as every situation is unique.

Edited 1 time(s). Last edit at 05/27/2015 07:21AM by itchytweed.