J
John Popelish
- Jan 1, 1970
- 0
john said:[...]
Thanks John. Good words.
I've enough now to try out on my stepper driver model.
Another note.
I think the switch in my design was driven by something that
was effectively a D or J-K flip flop (though there were two
of them inside an integrated dual H bridge chip), clocked at
the peak of the sawtooth clock waveform, with the D or J and
reset driven by the current comparator. So each clock
period, if the comparator showed current below reference,
the clock edge would start a power pulse, and when the
comparator showed the current above the reference, the reset
would terminate the pulse, and that decision was irrevocable
till the next clock edge began another pulse. The clock
circuit consisted of an external RC, in parallel to ground
with a fast charge and an RC time constant discharge. I
added a bit of that waveform to the current reference input
to make the sawtooth version of the current reference.
I wasn't micro stepping the driver, but operating in half
step mode. I also varied the average reference level
between two different values, depending on whether one or
two windings were being powered to produce a uniform break
away torque, regardless. This took a lot of rotational
torsional vibration out of the rotation.