Maximum distance between stepper motor and driver

Question

I have a motor setup with the driver DM556T close to a stepper motor (model 34IP65-120)(<2m cable length) on 24V@10A power supply. Due to certain circumstances, I have to separate the driver for a distance (~30m). Is that feasable to drive stepper motor from such a distance? The microcontroller that send control pulse is still close to the driver, just that the driver has to be distanced away from the motor. If not mistaken, driver uses PWM to control motor current, so I am not sure if PWM still reliable on such a distance. Or if anyone has such experience before? Will it skip steps or having unexpected behavior? Should I increase the stepping size to lower the switching frequency?

Answer 1

I wouldn't be so worried about the current budget of the wireing, but it also has to be considered. Use wires that are thick enough. Usually 4A/mm2 is a good estimate, so in your case i would go with 2.5mm2 wires. that will work.

I would worry more about signal integrity, like you pointed out. Driver does not send PWM to the motor, it is a similar signal but not exactly the same. Depending on wheter you are using micro- or half- or full-stepping the signal to the motor will be different. see below:

Full article is available here.

What's important here is that basically you are using differential driving in all cases, meaning A- is always negative vaule of A+, if measured toward 0V (which is not connected to the motor). That is, if A+ is 70%, A- will be -70% and viceversa. This is important for you, since it means you can treat this differentially. I would suggest twisting cables for A+ and A- and B+ and B-. This will create a twisted pair that will be resilient to outside disturbance, since any disturbance is induced into both A+ and A-, which results in the same voltage between A+ and A-.

However, it is still quite tricky and there could still be issues. A couple of things i see:

• long wires will increase inductance of the load. I don't know the specific driver well enough to know how it will act.
• You will be driving 10A over a wire that's 30m long which will create quite a big field around the wire, both magnetic nature ("sine wave" of microstepping) and rf nature (fast changes of steps have to include frequency components that are quite high in order to make the quick change). This can cause significant EMI issues with other devices around you. If you need to certify this device to any EMC standard this will almost centrally be an issue. If you don't and IF devices around your setup are robust enough there will be no issues.

At any rate i see this as potential issue, and that's why drivers are usually placed as close to the motor as possible.