RE: [CAD_CAM_EDM_DRO] High Voltage servo cards

Thanks Jon, if I get this right it means that I cannot run mach, it would
have to be EMC or something like that which I think controls all the PID
from the PC rather like the old anilam controller.

I haven't really looked at this properly, so please correct me if I'm wrong
as I know you will.

I haven't heard of such a plug in for mach.



As to Rutex in the third quadrant, this hasn't been a problem for me. If you
use the limit switch inputs to the Rutex card, it does a massive
deceleration and the current can peak quite hi possibly as you say hi enough
to knock the fets out. On my machine if it triggers a software limit switch
I use mach to decelerate it, at the same rate as acceleration so should be
OK. If it hits an Estop I drop all the DC power to the motor and control
power to the card, many don't like this but it works every time, the screws
on the mill are tight enough to bring it to a quick stop, and the motor
can't generate more volts than it's RPM so is within the characteristics of
the fet diodes. When I have had problems is when the limit switches haven't
worked, and the card has bumped up against the end stop on the mill, one
time this happened very quickly, the other time it was slow, but the
integral kept upping the power to the motor since it was stalled short of
position until the fets popped, the current limits never triggered even
though they were set to 15 amps. I heard it still humming, enough to think
is it still humming, I better push the stop switch, by which time the drive
was dead.



If I can run yours with mach without a long development schedule I'm
interested, if not, then I'm going to have to think some more. I don't
really want to go learning another system, got too much other things to do
as I'm sure you understand.



Thanks again

Mark





Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Jon Elson
Sent: 02 April 2007 06:41
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: 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





[Non-text portions of this message have been removed]