Stepper driver 1.2 behaves erratically

Hi All,

I've made a bunch of v1.2 boards and facing some peculiar problems. Namely, the boards first worked and then suddenly for every mm i try to turn the motor it rotates few full revolutions before stopping. I fiddled with the current settings but it is not quite back on track. Now the coils are energized even though enable pin is pulled low.

About the build, the board was professionally manufactured by the board house and i hand soldered everything. Few compromises are made due to unavailability of exact components. I put metallic capacitors where ceramics are used and instead of 10K trimpots i used 10 K ceramic preset.

Have anybody faced such problems ?

Thanks in advance.

Kannan

Seems like you have the steps per mm configured for a screw drive rather than a belt.

What do you mean by a "metallic" capacitor?

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[www.hydraraptor.blogspot.com]

Hi nophead,

Thanks for the response. Metal polyester i think, it has got yellow shiny paint over them. That particular axis is designed for lead screw and the same driver worked a while ago (;. I just removed it from the support to do some other assembly and put them back, that's all i did. This is the second board that went this way. Usually i handle the boards by the edges, so there is no chance of sudden discharge of static into the circuit. Suspecting some tracks got cut while flexing the board, i just checked all the traces as far as i could, but the problem persists.

As suggested in the reprap pages, i shorted the two places where 4.7 ohm resistors stand, could this be a problem ? I am splitting my hair at this moment trying to figure what the heck went wrong.

I tried to save some money by doing this board myself because the ready made ones cost three times more than this board. Now thinking about these troubles.......mmm. Of course i turned the axis few times by hand when the power is not applied, could this have destroyed L298, because of the back emf? the LEDs next to the motor connector glowed alternately while doing this.

Initially when connected to arduino, which by the way loaded with reprap firmware, the motors are disabled. However after the initial movement some residual voltage is present on the coils always and this draws lot of current and the heat sink becomes hot even though the enable pin is pulled low a long back.

Any suggestions are welcome.

Kannan

If it turns more steps that it should that implies noise on the step signal or the ground.

Turning the motor should not damage it because of the 8 diodes.

The chips are not very ESD sensitive, so unless you noticed a spark you probably didn't damage it that way.

If it stopped working when you turned the current pot perhaps you exceeded the maximum current rating. Certainly if it draws current when not enabled that is not a good sign.

Edited 1 time(s). Last edit at 10/07/2010 11:57AM by nophead.

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[www.hydraraptor.blogspot.com]

Both Arduino and stepper drivers are powered by ATX power supply and signals are routed through flat ribbon cables, so i don't that should be a problem. The other board is single sided and works like charm every time.

Any ways, i'll stick to the old boards for now and get back to v1.2 when time permits.

Thanks