Re: microstepper drives

[Mark Rivers <RIVERS@cars3.uchicago.edu>]

Pete writes:

> We tested for noise with a specific chopper microstepping motor driver
> by assembling a scintillation counter chain (amplifier and power
> supply) near the microstepping motor driver and observing the counter's
> amplifier output on an oscilloscope.  Depending on where we positioned
> the scint. counter, we observed modest to beaucoup noise.  This noise
> factors into the counting chain as background.  In the worst cases that
> we observed, the noise was at the same amplitude as the signal so that
> using a PHA or SCA to filter the noise would not be able to
> discriminate it out.  If we had been using a different type of
> detector, such as an ion chamber or unbiased photodiode, we would not
> have been able to filter it anyway.
> 
> We (UNICAT) have got to choose a different technology than chopper
> microsteppers.  Don't see any debate about this issue.
> Thought that this problem is likely to be of importance to the
> community of microstepper users here at APS and elsewhere.
> 
> We've observed this noise with:
>   Advanced Control Systems SPD-3M microstepping motor driver
>   Compumotor OEM650 microstepping motor driver
>   Newport MD4 microstepping motor driver

There is no doubt that chopper drivers generate noise.  The question is
whether with reasonable care one can make this noise insignificant.  Putting
drivers in different racks from amplifiers, using shielded cables and watching
cable routing might be easier than abandoning chopper drives.  The only 
non-chopper microstepper I know of is the Highland Technology one which SRI
has tested and written software for.  Using it means you can't use your OMS
drivers either.

Mark Rivers

CARS