The best stepper driver??? was Re: Stepper questions

The power section of the G201 uses 100V rated components minimum.
Some are rated to 600VDC like the half-bridge drivers. The mfgs of
said components throw in an additional 15% above rating to CYA. Net
result is the drives don't come apart until you hit 114 to 116VDC
supply.

We derate to 80% of max component voltage. That is a prudent value.

The drives are rated at 7A max. We use 33A rated MOSFETs. Seriously
derated there. Mostly to utilize the very low conductance losses a
33A part gives (0.04 Ohm on resistance) to keep heating losses low.

Net result, a drive you can seriously expect to reliably operate at
max rated voltage and max rated current simultaneously without ever
coming close to "bust the drive" limits.

Specialty ICs, as a lot of step motor ICs are, have overly optimistic
ratings. My experience with them left off with the L297/L298 chip-
set. Though rated at 2A they were useless or worse over 1A. That
soured me on the monolithic approach to drive design.

There is nothing better than using discrete TO-220 power devices that
are grossly over-rated in voltage and current ratings to design a
reliable drive. This way you are never even near the edge.

If I was crazy, it could be touted as a "100V, 33A step motor drive".
Some do that. I'm not so it's an "80V, 7A" drive instead.

Mariss



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
<dave_mucha@...> wrote:

>
> -
> > IMO the early xylotex were not as robust in actual shop use, as

the

> > other two. There was also a noise problem in the step/dir inputs
> > which Jeff to my knowledge has fully corrected in present boards.
> > Saying they were not as robust may be an unfair assessment, since
> > their popularity meant a larger sample and response was presented

in

> > these groups where much of my NON-personal experience is gotten.
> >
>
> The A3977 chip is listed as 35 volts and 2.5 amps.
>
> as I understand, the drivers on the Gecko are rated at something one
> the order of 100 volts, but the assembled unit has a manufacters
> rating of only 80 volts. a 20% de-rating of the components.
>
> In the early days of the Xylotex, many people tried to supply near

35

> volts and with any back-emf, 36 volts was all to common.
>
> I find fault in the understanding of the parameters of the chip and
> Xylotex has since, as I understand, recomended 24 volts as the

desired

> power supply.
>
> Dave
>