Run a stepper from 2 DM542 drive

**Snowtech** · 13-12-2021

But, depending on the weight, disabeling the Z-axis may cause it to lose position.

**BeagleBrainz** · 13-12-2021

Yes a very good point.

**A_Camera** · 13-12-2021

If losing position after switching is a problem then you need to zero after each switch. Regardless how you do it you can't expect that the position is the same after switching.

However several people mentioned switching only STEP and DIR. That will not work well. You MUST also switch the GND as a minimum, but if you use the EN for any of the drivers then you must include that also.

**BeagleBrainz** · 21-12-2021

They're have been a couple of methods put forward.

Unfortunately with no actual information on the controller boards only a generic answer can be given. The actual way to implement a specific method is up to the person/persons that have the hardware sitting in front of them. That's usually the situation with these issues. A question is asked without a lot of information regarding the hardware involved so only a generic answer can be given.

Maybe the best answer would be to ask the person/persons that designed your setup, or try and think of a way of not having to change the stepper driver or inputs.

The best option would for the main control software\hardware to operate\adjust the Z axis and be able to read the output from the system that adjusts your focal length. Of course this would depend on the main control software\hardware.

**Kitwn** · 21-12-2021

I assume you are manually selecting between the two devices rather than using both systems at once. Then I would suggest using a single driver with step and dir inputs switched as previously suggested but use standard logic gates to do the selecting between sources, possibly with optical or other isolators on the inputs to keep the grounds of the two boards separate if required. Power the logic and provide it's ground from the same board that powers the driver.

This way you could avoid any contact bounce on a mechanical switch and remove the need to common the logic grounds of your two boards. The enable line (if used) could also be buffered/switched/maintained during the changeover by your logic if required.

**dazp1976** · 22-12-2021

Diagram looks like some kind of 4 pole contactor type where the coil activates all the contacts at once.
Positioned all 4 NO for UC300 use and NC for arduino.

I'd suggest the most used one of the 2 controls be on the NO side then power the switch to the coil to flip it NC for the other.

Step/Dir could be a problem if the logic I/O flips with contactor switch over could it not?.

**A_Camera** · 23-12-2021

Originally Posted by dazp1976

Diagram looks like some kind of 4 pole contactor type where the coil activates all the contacts at once.
Positioned all 4 NO for UC300 use and NC for arduino.

I'd suggest the most used one of the 2 controls be on the NO side then power the switch to the coil to flip it NC for the other.

Step/Dir could be a problem if the logic I/O flips with contactor switch over could it not?.

I don't know what would be the point of changing to your suggestion. The way I do it works fine. The switch is manual, has actually nothing to do with Arduino. Step/dir/en is controlled by Arduino or UCCNC, depending on the position of the switch. Why would Step/Dir be a problem...? As I said, it works and I use it.

**Neale** · 23-12-2021

But surely the original question concerned one stepper and two drivers? And that's the question that's been answered - best way is one driver, one motor, and switch the inputs to the driver. However, the precise way of doing this - couple of logic chips, relays, switches, etc - depends so much on what you have already. Need to isolate common grounds, whether opto-isolation is needed, a bunch of things like that, are trivial to sort out - but only with a full understanding of where you are coming from, and I appreciate that this is difficult for someone with no knowledge of electronics so no insight into what info is needed.

But please don't change the question!

**gabi68** · 23-12-2021

Hi,

I din't change the question. I simply follow the advices given. Now I understand is easy to use one driver and switch the inputs. Sorry for confusion since I am very new to this and obviously electronic circuitry are not my forte (IT software background here).