Re: [CAD_CAM_EDM_DRO] Re: determining stepper motor current

Alan,
Meter??
I hope you know that you can't use an ampmeter to measure motor current.
It's chopping at ~20kHz.
The best way is to calculate based on the sense resistor value as given
before and set the VRef pot accordingly to needs.
I don't understand the 1.2 vs 3.4 diff unless your ohmeter is ??? or
the diff is that the higher reading is across a center tapped coil.
RichD


alanhunt2001 wrote:

>
> Hi Rich
> Thanks for your help - will try upping the peak current.
> Although the label says 1.2ohm, each coil actually measures 3.2ohm
> so I think this will give about 2watts? But my meter shows that I'm
> sending 0.2A (is this the average current through coils??) at 32v.
>
> so 0.2A x 3.2ohm =.64v and 0.13watt I think its a question of
> using either peak current or average current in the equation.
>
> I wish I had measured vref on the old board before removing all
> components from it and as the board contained a multitude of
> components for changing vref through software I can'nt even
> reconstruct the schematic easily!!
>
> Thanks again
> Alan