initialisation of 7344 cards

[Pascal M]

I am using NI 7344 cards and 7604 power drives and Motion Software. I am trying to force the number of steps of a stepper motor so that if I switch the power drive off and put back the value I had just before I switched off in the required number of steps and run the VI, the motors do not move? Is that a number to set somewhere when I reinitialize the cards?
Thanks

[Amaury]

I'm not sure that I get exactly what you are trying to do...but let me point a thing or two out that might help.

1. The position is traked entierly by the motion controller (7344) so powering the drive on and off should have no effect on the position reading as long as the motor does not move while the drive is off.

2. In relative position mode: if I am at 2000 and more 2000 I will end up at 4000.
In absolute position mode: if I am at 2000 and I go to 2000 I will not move (sounds like what you are trying to do)

To switch between absolute and relative position mode use the set operation mode command.

I hope this clears some things up. Let me know if you have more questions.

Regards,
Amaury
NI Applications Engineer

[Pascal M]

Dear Arnaury,

Thanks for the info.
I found that if you are at an absolute position of say 30000 steps, then switch off power drive AND PXI crate containing the 7344 cards (this can happen if a power cut occurs), when you read the position again, it reads 0 and not 30000 (I do not have encoders). So if you send 30000 steps again (and I do not want the motor to move) it will of course move because it thinks it is at 0.
Anyway, I have actually found a way of doing what I wanted by using the "Reset Position.flx" and reset the number of steps to a non zero value (like 30000).

[Amaury]

This is correct. If the controller and not the drive loses power you will lose any record of the position you were at. If you happen to know it then you can do exactly what you do, which is load the known position. However if you do not know it you must run the motor to a known location identified by a limit or home switch.

I think you've got the idea.

Best of Luck!
Amaury