Re: [CAD_CAM_EDM_DRO] CNC hydraulic test

> Hello Friends, For years I dreamed of converting the hydraulic
> control of my copy lathe into CNC. Right now I have 2
> electronically driven proportional valves sitting on my table
> together with the driver boards. The client permits me to make a
> test for my project before I shall install them in his machine. The
> input is -10V...0V...+10VDC but I have no computer with interface
> cards. Has somebody an idea how I could make me a simple test
> set-up to find out if these proportional valves would do an
> acceptable job in an CNC application?

Assuming a proper test means closing a servo loop (via some sort of
encoder feedback) through a PC, then you need some way to generate an
output voltage.

Two obvious choices come to mind:

1) get a byte input, 12 bit output A/D chip like the PM or AD 7548,
etc Hang this off the parallel port. You'll need one op amp to
generate an output voltage (the DAC's are current-mode) and probably
another to level shift to get the output range right. Hack up EMC to
control that and get feedback from the Kulaga DRO board, or write a
simple stand alone servo loop test program. (I could send you modules
for the linux 2.0.x version of EMC as I wrote something similar to use
these chips on an old ISA card I found in the trash at work)

2) build a PWM 'analog' output either via direct software timing or
controlling a counter chip. Integrate the output, amplify and level
shift with some op-amps, and control your servo.

Chris

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
http://www.mdc.net/~stratton
NEW PHONE NUMBER: (617) 628-1062 home, 253-2606 MIT