Motors don't have smooth movement

I have a prusa with theese motors and a sanguinololu 1.3a. I have the belt disconnected for testing.

The motors stop moving smoothly (see video) at seemingly random times, however the slower the motors run, the more likely it is to happen (usually within ~2 seconds or ~3 rotations).

I have tried:

• different motors
• Sprinter and Teacup firware
• removing everything but 1 pololu and 1 motor
• different power supply
• load on the power supply
• switching around pololu order
• setting the pololu pots at 0.4v
• setting the pololu pots a little more/less that 0.4v
• different amounts of microstepping
• heatsinks on pololus
• adjusting step skip in firmware
• Double checking sanguinololu solder joints

Edited 1 time(s). Last edit at 11/25/2012 02:09PM by peqo.

Hey peqo,

I think I may have a solution for you. Did you build the pololu driver boards yourself?

If so (and I guess even if you bought them from someone else) you may find that the problem is in the soldering.

The fact that it's worse when it's slower is key because stepper motors use more amperage to hold the motor position than to spin it.

I had a similar problem that was intermittent and I think it was related to the heat sink warming up enough to give off just a little amount of heat. That caused what had been a cold solder joint to separate and cause the voltage to have to arc to the pin from the board (I assumed).

Once I reflowed the solder at the pins the operation has been smooth for several months.

I'd suggest taking a magnifying glass to your driver boards and checking that and all of your connections to make sure everything is lining up and making good contact.

Edited 1 time(s). Last edit at 12/01/2012 07:13AM by a_shorething.

Do the chips get too hot to touch? The most likely explanation is current is too high and the chips go into thermal shutdown. Check that the sense resistors on the Pololu are 0.05R, i.e. labelled 005, Not 0R links as some clones have.

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nophead Wrote:
-------------------------------------------------------
> Do the chips get too hot to touch? The most likely
> explanation is current is too high and the chips
> go into thermal shutdown. Check that the sense
> resistors on the Pololu are 0.05R, i.e. labelled
> 005, Not 0R links as some clones have.

They aren't too hot. However, the only labeled resistors are either "POC" or "3OC".

a_shorething Wrote:
-------------------------------------------------------
> Hey peqo,
>
> I think I may have a solution for you. Did you
> build the pololu driver boards yourself?
>
> If so (and I guess even if you bought them from
> someone else) you may find that the problem is in
> the soldering.
>
> The fact that it's worse when it's slower is key
> because stepper motors use more amperage to hold
> the motor position than to spin it.
>
> I had a similar problem that was intermittent and
> I think it was related to the heat sink warming up
> enough to give off just a little amount of heat.
> That caused what had been a cold solder joint to
> separate and cause the voltage to have to arc to
> the pin from the board (I assumed).
>
> Once I reflowed the solder at the pins the
> operation has been smooth for several months.
>
> I'd suggest taking a magnifying glass to your
> driver boards and checking that and all of your
> connections to make sure everything is lining up
> and making good contact.

I think this might have fixed it, still have to run some more tests though. However, now the motors move quietly, after they stop there is maybe 1 second of silence and then they make a noise like a car engine revving up. It's quite loud too. Tried 0.4v on trim pots, tried more/less too.