Re: need help, brushless drive

> The downside to those drives is that they are appear
> to take an analog control signal. So you have to get
> that from somewhere, either D/A converters or the
> Rutex Step/Direction to analog converter.
>

Not a downside there, since I just got Abdul's new PCI motion control
card with EMC support and 8 channels of DAC. I *wanted* a drive with
analog control input!

> If it was me, I would seriously consider trying to get
> the drives to work through experimentation. It's
> somewhat unlikely you would smoke anything before it
> faulted. You may have a problem in the halls
> configuration. There are 2 configurations of halls
> (60 and 120 degrees, I think). The drive will fault
> if it doesn't like your motor's configuration. The
> trick is to figure out which combination of halls goes
> with which motor winding.

Good point, but the halls should be easy enough to figure out by
trial and error.

> The other issue is that it appears that you need to
> supply an unknown voltage for the opto reference and
> the shutdown input. I would guess ground for
> reference and shutdown at 5,12, or 24 volts in that
> order.

This is mainly what I wanted the manual for, to see what the drive
expects for the shutdown interlock. Well, that and the halls and
stuff. At least I have the pinouts, which is more than I can say for
some drives I have, lol.

>
> Finally, since nobody ever made a brushless motor with
> a tach and stayed in business long enough for their
> motors to be common on Ebay, you probably want to drop
> the tach gain to zero. Hopefully the drive will
> stabilize and not have too much torque ripple even
> without a tach. As an aside, some AMC drives use an
> encoder to simulate a tach.
>
> Regards,
> Eric

Yeah, I don't get it myself. I have bought about hmmm, six different
large brushless servo motors on ebay from various manufacturers, and
none of them have tachs. They all have encoders, admittedly nice
high count encoders, but still...

This leads me to the next little circuit I am going to build and make
available to folks on here, a small frequency to voltage circuit to
simulate a tach from an encoder count. There are some one chip
solutions to this, so should be a simple circuit board. I could use
about 10 of them just for the motors and drives I have, so I know it
will be a popular thing. It would be great if it can be made for $5
or so.

Thanks for the reply.

Rick