Re: Axis Stall Problems

In my last post, I mistyped L298 instead of L297 every time in the
last paragraph. It should have read:

The top trace is the voltage across the .5 ohm sense resistor. The
bottom is the voltage at the sense input of the L297 (pin 14 in this
case). The L297 pin 14 signal is filtered by a 10K series resistor
from the sense resistor and a 680pf cap to ground. The scope is set
at 10 microseconds per division and .5 volts per division. The L297
oscillator is about 18KHz (in fact with the 56 microsecond period,
it's 17,857 Hz). The stepper is a Powermax II M21NRXA, 8 wire,
running the coils in series. The specs for this configuration are
phase resistance .92 ohm, inductance 2.8 millihenry. I took these
with my digital camera, so it's hard to see the slope of the top
trace exactly, but there is a little rise after the ringing stops.
The reference voltage into the L297 is .240 volts, and it trips at
just about that. This circuit has a "holding current" reference
voltage that kicks in after a small delay without a step pulse, and
the traces show the "holding current" configuration (with about .48
amps current into the still motor).

Irby