I’ve been running two stepper motors succesfully with my K8055 board using relays.
But since earlier today I’ve been experiencing some troubles when running them.
My issue appears to be semi-random, sometimes when I turn Digital Output 5 on, the card acts as if I had removed the usb cable from the card and then put it back in there. Digital output 8 will flash three times and my application will crash because it can’t send data to the card anymore.
The strangest of all seems to be that I am not experiencing this issue when I remove the power source to drive the relays and the stepper motors …
At first I tought it could be a magnetic field created by one of the wires that was messing with the USB cable signal, so I made sure no wire was parallell to it, to no avail…
Perhaps the usb cable loses it’s connection for a moment when the motor creates a vibration in my project board (the card is screwed down to the same piece of wood that the motor is bolted onto)?
It seems that the microcontroller on the K8055 board resets itself for some reason.
First you have to check the USB cable connection and all the soldering joints on the K8055 board.
Possible reason to this problem may also be some sort of electromagnetic disturbance either radiated or conducted from the relays and/or stepper motors you are driving with the K8055 board.
You may try to move the relays and stepper motors as far as possible from the K8055 card.
It may also be good idea to use twisted wires between the K8055 card and the relays (this reduces the radiation).
You may also add some small capacitors 10nF…100nF between the digital outputs and GND.
As you can see, everything is glued / bolted down to the piece of wood and all wires are cut to length. It would be a rather tedious process to redo the whole board.
I tried switching the two motors (putting the first one in the second one’s clamps and vice versa), and the one driving the disk is still resetting the microcontroller …
I have no problems with the first motor whatsoever…
I there another way to shield the card from radiation? Insulated aluminum foil or something :X
Yes, your system seems to be quite fixed.
There seems to be one black wire going under the K8055 board.
It may be the reason to the problem - or may not.
You can try moving it to go some other route.
Firstly I detached the motors leaving only the relays able to interfere with the card.
They posed no problems and the card happily made the relays tick.
I unbolted the second (disk) motor and noticed that the wires leading to it were coiled up (instead of clipped to size) I decoiled them and placed the motor as far away from the card as the wires allowed me too (about 50cm), to no avail.
I then feared that the wires surrounding the card might be interfering when current flows through them.
I then measured and calculated a bit.
The first (working) motor has a coil resistance of 4.8 ohms. Turning it at 12 volts translates into a current of 2.5 amps.
The second (interfering) motor has a coil resistance of 35 ohms. Turning that one at 12volts translates into a current of 0.35 amps
Measuring the amps when putting the motors under stress also gives these results.
Since the strenght of a magnetic field is relative to the current forced through the wire creating it, I can safely assume that the first motor should give even more trouble no?
The possibility of only certain wires creating obstructions can also be ruled out since I switched the motors (not the relays or the wires)…
Therefore I think I can rule the option of the wires interfering with the card out.
Should I move the motor even further? Or will this not help …
EDIT: I also noticed I didn’t illustrate what happens when the connection “breaks” very well. The eight test LED of the digital out array flashes as if the card is plugged back in but stays lit on the last flash.
EDIT2: Just noticed your reply, thank you for it. I detached the wire and moved it all the way arround the card, this makes no difference either.
Seems to be difficult problem.
You have noted that only the motor having coil resistance of 35 ohms is disturbing the system.
Maybe you have to try to move it even further.
