Need Help: Stepper Motor Hiccup

K.. I know thats really frustrating.. I had similar experiences..

Please let me know a few more things:

1. Its it just the controller you have or the drive is also alongwith the controller?

2. What is the frequency of pulses you are generating?

3. Whats the weight of your robot (aprox figure)?

4. Whats the torque rating of the stepper motors?

For the time being...

Try reducing the frequency of the pulses.. do a hit and trial... It takes time.. be patient..

Also I think youir driver is not able to sink enough current to run the motor (the torque issue!!)..

And if you can direct me to the stepper motor and controller page, it would be easy for me..

All the best..

thanks for the prompt reply Krahul. the problem was with the software of the motor controller. apparently the torque and voltage can be adjusted with a few lines of code. :-o So it runs fine now....no hardware manipulation needed! here are the links motor: http://www.robotshop.com/rbsoy14-soyo-unipolar-stepper-motor-1.html controller: http://www.trossenrobotics.com/phidgetstepper-unipolar-usb-4-motor-stepper-controller.aspx?feed=Froogle

If you have not used stepper motors before then it may be worth considering the following:

Obtain the speed torque graphs for the motor - its voltage rating etc. A 12V rated motor will not run fast under load as the back emf will limit the resulting voltage to pump the current into the windings. The supplier of the motor and the drive can help much more.

Unipolar drive is not the best for torque/speed requirements - if the motor runs out of assembly and not in assembly it is possible it is lack of torque or power that is the issue.

You can run it in bipolar mode by selecting the correct windings but make sure your 12V supply is capable of providing the (current) power necessary. There is also a current drive mode that controls the torque better by supplying more current but as the voltage is fixed make sure the motors are rated at 6V or 3V to obtain more headroom so current can be pumped in to produce the necessary torque at the speed required.

To check if the power supplied is sufficient try running the motor at slower rate i.e. low power demand mode. I am assuming the motor is capable of the torque speed requirements. This you can check with the graphs you will get with the motor and see if your pull in speed/torque and pull out speed/torque matches your design.

You have your fix, but here is a great tip:-

NEVER EVER dismantle a stepper motor, in a worst case condition it will never run properly again.....

There are many reasons but the main one is replacing the rotor without it touching the stator, an impossible job by hand.....

You can get lucky and it works, but I have also read that even then the torque may still be dramatically reduced in use.....

Not forgetting that (in your case at least) you have new motors with a guarantee that forbids dismantling them......

sorry for the late reply/correction, but i'm drunk and just thought of looking through my old posts. We DID NOT dismantle the motor, we disassembled--removed it--from the robot to test it independently. sorry for the confusion...I (and hope no one else) would never dismantle a stepper motor!!! The Robot did well in the IEEE region 5 competition coming in 4th place out of about 30!! woo hoo!!

"when we try to run the robot....it just doesn't!! It simply stays there and vibrates"

Does the robot consume a lot of alcohol? I ask this because this is exactly what happens to Uncle Hank especially around the holidays'.