Re: [CAD_CAM_EDM_DRO] 5-Phase steppers

Roy J. Tellason wrote:

> [my post snipped]
>
>Looks like you could do this real simply in hardware with a ring counter...
>
>

An FPGA would work well. Getting the initial conditions into a ring
counter (without screwing up later "counts") might prove problematic.
Using a $1 or $2 microcontroller is probably worth it instead.

>>If someone sends me a circuit diagram, I can lay out a board and write
>>some PIC or AVR code for it. (I'm an electrical engineer, but I've
>>always been more comfortable with the digital design/programming end,
>>not the power end of things :)
>>
>>
>
>Take a look here:
>
>http://caladan.nanosoft.ca/index.php
>
>under "circuit corner", one of the entries under there shows some H-bridge
>stuff. You'll need half an H-bridge for each of the five wires, parts
>depending on how much voltage and current have to be handled.
>
>

Heh heh. Thanks.
I know the general H-bridge circuit. It's the specifics I'd be looking
for :) That circuit would need a charge pump/high-side driver, unless
the control signals (X1 and X2) were able to get to the motor's
operating voltage, which is unlikely with a microcontroller or standard
logic. Also, current measurement is a PITA with a 5-phase stepper,
because you never really know which way the current will be going. You
have to have bipolar (bidirectional) current sensing on each leg of the
stepper if you want to be able to current limit.

I may take some time to write code to control a 5-phase stepper, but it
won't be for a while (I'm a little busy with S-corporation accounting
related things at the moment). It would probably be possible to use an
H-bridge chip or kludge together several other drives (like a few Geckos
or Rutexes) to get the required number of half-bridges.

- Steve