Need Help!- Motors not moving (Geckos 202.)

[stef_d]

I have been twisting my brains on this problem for a while now.
I am not getting any luck with my motors.
here is the setup:
from the parrallel port, onto some 541 TTL signal drivers. from which i pickup the step and direction signals, then onto the geckos G202, then the motors.
I have set the current sensing resistor to a safe 20K ( about 2Amps) and wired the hybrid motors in series (i have also tried parrallel).
The geckos are powered from a 70V linear supply, and the 541 drivers from a 5V supply. I wired correctly the step, dir and comon connections.

Here is the procedure:
5V is switched on, then 70V. Light on the G202 comes up. I use EMC2 to control the system. When i try to move any axis, nothing happens.
here is what i checked:

I checked all the wiring, and then i checked the wiring again.
I used a scope to check the step pulses were getting through at the G202 input. They do, so does the dir signal. At first, i though the pulses looked a little thin (too fast ?) so i slowed them right down, and got some really long, slow ones to the geckos. still no luck.
I checked the phase outputs, using the scope. I do get some 70V, nicely chopped signal through to the motors. sometimes on one phase only, sometimes on both. (i depends which G202 I am plugging into. I have 4 of them). So i guess the G202s are doing there job to keep the motors holding still. however, no change on the phase outputs when i press the jog key.
I swapped geckos, i swapped phase order..i must have tried everything i could think of.


The worse thing is that i did get the motors running during initial testing, about a month ago, just to test the G202s. the motors turned very well, without a single setup problem. I am now using the same supply, same motor, and same controlling software, but i cant solve the problem...
any idea what i should check next ?

[stef_d]

Ok, i had one more night sleep over it. It must have been a good night.
I worked out where i was going wrong.
The common connection is not common "ground" (otherwise, the G202 does not have any means of knowing the amplitude of a step pulse.. it could trigger at 2V or 3.3 or 5V).
common has to be the +5 ref from the 541. i checked the manual, and of course, it is.
tried this this morning, and i have motion !