Re: step pulse timing resolution

Terry writes:

>just a side question that is related to steppers.
>When the feed is altered using F does the motor really slow down or
>is just the pause in between the steps that just get longer and the
>actual time taken to move from one step to the other remains the
>same?

Terry,

Steppers are controlled by a "pulse train" which goes from hi to low
(nominally 0 and 5 volts, actually .8v Lo and 2.4v HI for TTL). Step
drivers "step" on the transition FROM HI to Lo (or from Lo to HI,
depending on mfr.)

_ _ HI ___ ___ ________ _______ ____
| | | | | | | | | | | | | |
___| |___| |___ Lo __| |___| |___ _| |_| |_| |_

Follow the ascii art above with your finger (tracing from left to
right)Now each time you go "up", a step will be sent to the motor.
(if the driver steps on the transition from Lo to HI) Other wise,
each time you go "down", the driver will step.

So you can increase the distance between the hi's, or the low's,or
both and the stepper will step more slowly.(there will not be as many
"transitions" per unit of time)

Usually either the tops(HI's) or bottoms(low's) of the pulse train
are kept a fixed length(time)and ,as you mentioned, the time BETWEEN
(pause) is adjusted to make the step motor go faster or slower.


With servos, the servo amplifier sends more or less VOLTAGE to the
motor in response to the pulse train, which causes the motor to speed
up or slow down.

Hope this helps.

Ballendo