Stepper questions:

I"ve just joined, and was looking for some specific information.

As an introduction, though, I've been working on several CAM type
projects: adding CNC to a unimat lathe, (eventually) adding CNC to a
Grizzly mini-mill, adding DROs to the same mill (got X and Z done,
will have Y done by the end of the day), and an XYZR table.

I found a bunch of L298 Dual full bridge drivers, and am looking into
the L297's.

Since I had planned to drive most of the steppers with saturating
darlingtons, this gives me another option.

I have the Fuji steppers (frame 23, I think, single stack, torque
about 150 in-oz) Fuji GPF-3945-2F. These are the ones with IBM part
numbers sold by Herbach and Rademan for about 15 dollars or so each.
On the XYZR table, I have two of them, and they work just fine.

However, I can now 1) run them bipolar at twice the voltage and the
same current (9.0 volts at 1.4 amps/phase). Other than possibly more
power dissipation than the motor is rated for, will I really get more
torque? If so, how much? If I then run them half stepping mode (easy
to do), that's (on the average moving) 1.5 times more dissipation to 2
(if not moving).... Anybody have an idea about this?

For the controllers, I may drive the 298 chips from an ATMEL
microprocessor, one per axis, controlled through the serial port. The
chip is smart enough to do a stepper controller, and pay attention to
limit switches.

Once I find the connectors for the DROs, I will be building a readout
for the mill, which will also have a serial output to go back to a
controller of some sort. I may end up rolling most of my own
software, but that all depends.

All the microprocessor work depends on getting the emulator finished,
though, the assembler is working.

Some details are on my website, reachable by www.netcom.com/~madyn and
go to metal, or if you wish a direct link to the metalworking site
(does not have the xyzr table), please go to
www.netcom.com/~madynmetal

Comments are welcome. I'm just sorta starting out in this. I tried
to go through the archives, but it's as bad as the 7x10 minilathe
group.....

Harvey