Sine wave for 5 phase 10 wire stepper (non-stared)

Hi

I'm building a new controller for a leath using EMC.

Most of the electronics in the leath were lightning struck, so were junk, the heavier stuff was OK. Using two parallel ports, I have every thing mostly working under control of EMC except the stepper motors...

They are apparently a high end (for their day) 5 phase motor with 10 leads in a non-stared configuration. The drive amps are OK, so will reuse them, but they need a +/- 8 volt 5 phase sine wave to drive them. The manufacture (South Bend) had used a micro processor to control 5 digital-to-analog convertors. This way they could make a sine wave that could be run at a wide range of frequencies and even frozen or reversed. Slick.

I dicided to follow their lead and do much the same thing, just with a bit newer processor.
Has anyone already done something like this? If so, do you have a design or any design tips that could save me some hassle?

I'm a bit undecided if it would be better to use step/dir. or speed/dir. control. It seems to me that speed and direction would be better as it would involve less communication between the PC and the signal generator via a parallel port.

I would have thought the deciding factor would be what EMC prefers to control them with. Creating a 5-channel sine wave from a step/dir signal using a current microprocessor with internal or external DACs is relatively easy and there's sample code around for ATMEL and PIC processors that would give you a head start (albeit 2 phase, but the concepts are similar).

As I understood it your choices are step/dir for stepper drivers or speed/direction plus encoder so that EMC plays the part of a servo controller. I suspect the latter is infinitely harder to get working effectively and efficiently but no doubt someone will be along in a minute to contradict me...

Yes I had to generate multiple analogue control voltages with a micro.

I used atmel ATmega16 with linear technologies D/A converter chips sitting on I2C buss.

All A/D chips sit on same clock and serial data line the micro uses one of the ports to select which A/D is to be updated.

You can write a look up table to do the appropriate D/A output , a modulo 5 counter to select the correct channel and voila Bob's Your uncle.

The beauty of this scheme is that the D/A converters retain last analogue value
This gives You a fairly quick update rate for a five phase output.

from memory update rate was about 14 clock cycles per channel.

I used this to control gains and AGC loops in an RF signal processor but same same