Re: [CAD_CAM_EDM_DRO] High Voltage servo cards

Mark Vaughan wrote:

> I knew you had some Jon, and Yes we have discussed this many times.
>
> I didn't know these were yours, I thought you kept them for your own use
> because they were expensive.
>

I had a non-commercial project in 1998 or so and built a
velocity servo amp with a Pulse Width modulator and FET output
stage. These are in my Bridgeport mill. I sold a couple dozen
bare boards and instructions to others that wanted to build them
and learn the ins and outs of servo amplifiers. Compared to
Copley Controls' 400-series, I decided they were not
competitive, so I never marketed them as complete units.

After designing my Universal Stepper Controller, it ocurreed to
me that a PWM generator was not really that different from a
hardware step generator, so I hacked up one of the old servo
amps and changed the UPC's FPGA configuration to do PWM, and was
very happy with the results. It was a MUCH simpler servo amp,
and a pretty simple controller.

> I was hoping you would come in with a suggestion, seems you've already
> experienced every problem the rest of us have which means you've had good
> chance correct them.
>

Yes, I made the same mistake in 3rd quadrant operation that
Rutex has apparently made (when the drive is braking the motor
and the current reaches the current limit, it shorted the motor,
which caused current to RISE instead of fall!) OOPS! So, I had
to redesign the board to open-circuit the motor under that
condition. Much better servo response, as well as no blown
transistors.

> I also get a good honest answer from you all the time.
>
>
>
> Your PWM board, I take it that takes normal Step Direction signals in from
> parallel port, so I could run it from My G100.
>

No, there are NO STEPS anywhere in the system. The PWM amp
takes a 50 KHz digital signal with varying pulse width. The UPC
generates this signal on command from the PC. It also sends the
encoder position to the PC at 1000 times a second or more.

> What max frequency step rate can you take in, though if its like your
> encoder rate at 300KHz it will be OK.
>
> My motors are SEMMT30U4-57's,
>
> 57V/1000PM, 140V but I have a 160V supply which SEM say is still OK,
>
> 40lB/in TENV stall torque, at 8.3 amps without forced cooling.
>
> Peak stall talk 192lb/in at 47 amps, Armature 1.1 Ohm less brushes, 8.1mH
>
> Do you see any problems here.
>
>

My servo amps are rated for 20 A peak, and about 15 A
continuous. I have tested them up to 120 V DC, earlier I had
some problems at 160 V, but I really need to test again for
that voltage.

>
> Lastly you have a price for the motion PCB at $250, what price are the servo
> cards, and I suppose shipping to the UK.

The normal amps are US $125, but I might have to supply a
special version for use above 120 V. Probably that one would
be $140.

Jon