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re: Stepper motor transition board
Matt Stettler at LANL AOT Div (formerly AT Div), has really nice, modular,
rugged hardware designed specifically for the OMS Motor Controllers. The
set of hardware includes: a 6U transition module from the controller P2 conn
to the drivers, a 3U rackmount chassis with power and the OMS signals bussed
across the back, driver modules (one per motor) that slide into the 3U
chassis, a power supply and cables. Matt has hardware to support the following
OMS motor controllers: VMEX-4E, VME44-4E, VMEX-6, VME8. Unfortunately OMS
did not follow a consistent pin layout on the P2 from all the controllers,
so different connections are required for each OMS board. The hardware
supports encoders (if the OMS controller does), brakes, and optional reduced
holding currents.
The transistion module is a 6U form factor (I would go with one of the VME
standard sizes, 3U or 6U, for a any new transition module, rather than
introduce another size by choosing 4U), that takes the OMS controller P2
connections from the backplane to a front panel DB-37 (VMEX-6, VMEX-4E) or
DB-50 (VME44-4E, VME8). It does not go to the steppak connectors.
Noise problems are addressed in two ways: 1) the board drives differential
signals over the field wiring to differential line receivers in the motor
driver module electronics, getting rid of the problems of noise spikes
on the lines; 2) the signals are also opto-isolated on the transition module.
Using this transition module with the StepPak would be possible if some
electronics were added before the StepPak to receive the differential
signals. I have schematics and some artwork (hardcopy) for all of the
hardware. Matt has always been willing to provide any information I've
needed, and even make design changes where necessary. LANL designed and
built the VME44-4E and VME-8 hardware at our [APS] request. However,
since Matt doesn't foresee using StepPaks at LANL, he wouldn't be that
interested in doing the design work himself.
The hardware costs for a fully populated VME-8 system, including transition
module, driver chassis and driver modules, power supply and cabling runs
between $1050 and $1400 per motor axis, depending on the power requirements
and microstepping capability needed. I think the transition boards themselves
cost about $650 each (for 8 motors). Centent has recently announced a
brush-type DC motor driver that is pin-compatible with the Centent stepper
motor drivers used in the LANL hardware. I plan to buy one and provide it
to Matt for testing. Matt, Susan Barr and I have already arranged for Matt
to demo this hardware at the User's Meeting in May.
Karen