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[on:]

Hey!

I ripped appart an old printer and took out a stepper motor which I am trying to control (Datasheet: http://www.eminebea.com/en/product/rotary/data/pm55l048.pdf)
I am controlling it with an L293D control chip and it's working-ish.

I have a little program running which spins it forward, then back, then forward, then back etc. The first few loops of this are fine and it spins as expected, but after that I start to get a juddery-ness when the motor is in reverse. Coincidentally, this juddery-ness occus at the point the L293D gets almost too hot to touch (yes, I should have a heat sink, silly me).

This is odd because it only occurs when the motor is in reverse so I'm not really sure what explanation it could be. I have come up with a few ideas but I'm not sure how to prove any of them:

1- The L293D is overheating and therefore in someway makes the motor juddery (but why only in one direction?)
2- The motor is broken in some way (but it works fine at first)

I hope someone can shine a light on this

Thanks for reading

[Edit P.s I'm actually running it at 12v not 24v at the mo]

[Reply #1 on:]

The datasheet shows two different versions, I think, can you measure the windings' resistance to see if its 5.5 ohms or 30 ohms?

Also what voltage are you using?

[Reply #2 on:]

If it happens after the LM293 gets hot, then it would be safe to assume that you have a problem caused by heat. 

When the device gets hot the characteristics of the internal transistors change and they don't switch on and off cleanly. Or they might even try to stay on.

You are drawing too much current.

[Reply #3 on:]

Sounds like  what I'm running into, using a TI ULN2001P (pin for pin, it's identical to the ULN2003, but it seems to be lower voltages. (5V)..)

I pulled the 2001's from a old printer main board.. can't remember if the steppers were 7V, 5V, or 3V..

[Reply #4 on:]

If it happens after the LM293 gets hot, then it would be safe to assume that you have a problem caused by heat. 

When the device gets hot the characteristics of the internal transistors change and they don't switch on and off cleanly. Or they might even try to stay on.

You are drawing too much current.

Ok, that's what I suspected. Might this: https://www.sparkfun.com/products/315 be better?

The datasheet shows two different versions, I think, can you measure the windings' resistance to see if its 5.5 ohms or 30 ohms?

Also what voltage are you using?

The resistance in the windings seems to be 24.5 ohms so I assume it is the 30 ohm version although I'm not sure if that makes a difference?
I'm using 12 volts as 12V seems to do the job

[Reply #5 on:]

Anyone?...