Stepper Drivers

The ballscrew is on order, so it's time to worry about other parts of
the system, principally how to push around 5 amps through a stepper.

A couple of options:

1) If I limit the supply rail to below 20V it's comparatively easy to
make a full H bridge using N and P channel MOSFET's. The 20volt
limitation arrises from the maximum VGS of the P fet without
complicated floating circuitry to drive it.

2) If I were to limit the system performance to 4 amps I could use an
L6203 bridge IC.

3) I could use a pair of International Rectifier IR 2103 triple half
bridge drivers ($11 each) [well, 4 chips gets 3 axis] and 8 power N
channel mosfets per axis. The circuit looks simple, and it will
handle any reasonable supply rail.

4) I could use a cheaper full bridge driver HIP4080 ($6) at moderately
high supply rails (up to 80v) along with 8 N channel MOSFETS per axis.
According to the data sheet, I would have to build extra circuit to
prevent the bridges from shorting on power on. (Hm, tempting instead
to put a relay latched "Motor Enable" button on the box to activate
the motor supply rail - operater has to push after each power on,
won't work until logic/bias power is good).

5) I could just run the motors unipolar at about 2/3 the torque using
very simple electronics. 4 N FET's and something to boost the gate
drive voltage per channel... It's very tempting to build such a
unipolar system to start! Is there a reason I don't want to do this?

What kind of supply rails are people running anyway?

Chris

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
30 Griswold Street, Cambridge, MA 02138
http://www.mdc.net/~stratton
(617) 492-3358 home/shop