Hi,
I need help. I have been in electronics design for almost 20 years but this is getting me down.
I had to design a stepper controller for a linear actuator from Haydon. It has a worm screw and a nut and it is used to lift a panel to exact positions. I have a controller/driver chip like PBL3717 and I drive it from a Micdoprocessor . The controller chip uses a chopper drive with the 5V motor running off 40V @ I max=560mA Motor is 200 step/rev bipolar.
I am stepping in fullstep mode with 2 coild nergized at all times. The 4 step phases are: A1A2 B1B2
0 1 0 1 0 1 1 0 1 0 1 0 1 0 0 1I am stepping batches of 400 steps at a time and I repeat this over and over.
I use a accelerate and decelerate routine as follows:
Step 0-23 = accelerate 0 to 635 stpes/sec Step 24 - 374 = run at 635 steps/sec Step 374 - 399 = decelerate to - and then stop.
Problem: Motor starts runs and stops correctly but as I repeat the batches of 400, suddenly, RANDOM (!) motor starts and runs at a higher (audible buzz) speed in the opposite direction. This is NOT caused by the drive sequence or anything in the pulses. In fact, there is no electrical difference at all in the driving. The motor just does his. The next batch will be ok again. Sometimes it works fine for 30 an dmore batches and suddely it does it again.
Has anyone come across a problem like this and how is it best solved?
I tell you, stepper motors are not simple when resonance, acceleration and exact position all come into it simultaneously!
Regards Bernt