Erratic Stepper

curious1

Hello Folks,
I am running 2 steppers with the BS2.
Pulse and direction to each using 4 pins on the stamp.
1·common power supply, only 1 motor runs at a time.
All runs well, the problem occurs when I turn the power off to the stamp and leave the power supply on to the drivers.
One motor holds position steady as a rock, the other one, after a few seconds, buzzes and chatters wildly, then calms down for a few seconds, then goes again. I have to kill the power to everything before it passes its limits and crashes.
The drivers are different brands but basically the same. They have internal pull-up/dn resistors.
Any clues ???
Thanks

Mike Green

First of all, you are likely to get more useful help if you supply more information. Schematics and details about the pieces used are most important.

It's likely that there's something not right about the internal pull-up/down resistors in that the Stamp is off, yet one motor seems to be affected by noise and the other is not.

Phil Pilgrim (PhiPi)

I'm guessing you need pullups or pulldowns on the Stamp lines that feed the motor controllers. When you power off the Stamp, these lines are left floating and are very susceptible to noise. This noise translates into random commands to the drivers, yielding the erratic behavior you're seeing.

-Phil