Quote Originally Posted by Clive S View Post
I only have a 500Va toroidal running 68v DC with no problems
Ditto - although the transformer did go pop one day! But that seems to have been some random internal short as before that time it never even got warm. Those current figures are, to be honest, a bit vague. They don't really correspond with anything very much and in practice the load the drivers and motors put on the power supply is much less than your sums suggest. Hence my comments about motor temperature - for most practical purposes it's as good a guide as any! If you can hold the motor in your hand without it being too hot, then it's no more than 60C and that's fine for a stepper. It's what they do!

Your current/voltage sums are correct - power = volts x amps - but in this case, because the loads are pulses, of varying levels, and don't happen at the same time on all motors, then the average is lower than the sums suggest. In addition, using a linear PSU is a great idea as it is able to cope with short duration peak pulse overloads with ease, as long as the average load stays within spec. Translation - you can safely get away with it! Switch-mode supplies are cheaper, smaller, and lighter but do not like even very short duration overloads and go rapidly into sulk mode.

In your wiring diagram, connect A to C, -A to -C (can't replicate the exact terms in your diagram but I'm sure you can see what I mean), and then A/C to A+ on the driver, -A/-C to A- on the driver. Ditto for B&D. I think you know that you only then need four wires back to the driver.

I did have a strip of draught excluder brush with long bristles for my dust shoe but it was a pain to make - getting the groove right was tricky with the balance between too tight/too loose and bending the strip to fit was just a bit fiddly. My cheap and cheerful solution works at least as well and costs nowt into the bargain! That's an engineering solution...