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MaslowCNC / Electronics

This is the main control board for the Maslow CNC router. It is designed to mate with an Arduino Mega 2560
https://www.MaslowCNC.com
The Unlicense
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Add ability to drive stepper #39

Closed davidelang closed 6 years ago

davidelang commented 6 years ago

see https://github.com/MaslowCNC/Firmware/issues/355

since we are have four channels available, it would be good to add an extra header to the board that would let us use two channels together to drive a stepper (ideally using the same pinout that is common for 3d printers)

combined with a software way to drive this (even inefficiently), this would let people use off-the-shelf stepper driven Z axis kits/design with the maslow.

blurfl commented 6 years ago

This would involve a fairly major re-design of the board.

BarbourSmith commented 6 years ago

Yes, it would probably be easier to make a new board. I am going to add the tag wontfix because the suggestion is a good one, but we are not actively working towards addressing it

davidelang commented 6 years ago

On Wed, 10 Jan 2018, Scott Smith wrote:

This would involve a fairly major re-design of the board.

I don't think it would.

a stepper driver is two H bridges, one for each set of coils. The pre-built steppers add extra logic to simplify management of the two h-bridges so that you can have one pin for direction and another for step and the chip takes care of everything else.

But if we just were to wire the two H-bridge halves to one plug, the rest of the logic could be done in software.

It's not efficient, and not pretty, but I can't think of why it wouldn't work.

Remember, we are not needing microstepping here, the stepper (@200 steps/rev) is being connected to a lead screw (@8 steps/in or more), resulting in one step being ~ 0.00125". That should be more than sufficient for the Z axis. I'd expect that we could get by with a resulution 1/10 that (0.0125") without a problem.

So a simple state table in software that we step through to toggle the different combinations of power through the h-bridges should be easy to do.

Doing something to drive these at less than full power (pwm) shoudn't be that hard either.

blurfl commented 6 years ago

I'd call it a major re-design as it involves adding another connector and traces for the connector and the presently unused half of the second H-bridge. Further, the present design has spread the chips out for thermal efficiency, leaving no room for a fourth connector.

blurfl commented 6 years ago

If one wants to drive a stepper, look into driving a stepper driver board using two of the AUX pins. Logic power, ground, step and direction are enough for the Maslow side and are all available from the AUX pins.

BarbourSmith commented 6 years ago

Great suggestion @blurfl I think driving a stepper off of the AUX ports makes so much more sense and would be a much cleaner build. Ok to close this as a hardware issue and make it a software issue if we decide to go that route?

ProtoMakerOpenTech commented 6 years ago

Currently working on a maslow variant for the open source market. Going to work on keeping it as backward compatible as possible and will be building a new board for stepper control, support for a lathe axis and VFD. Anyone interested in contributing let me know. Most of my machine design experience is in the 3D printing space and came across the maslow as a possible tool for prototyping.

blurfl commented 6 years ago 
Currently working on a maslow variant for the open source market.

You might want to make a post over in the Maslow CNC Forum Hardware section, you will reach more eyes there. This particular issue is a candidate for being closed.

blurfl commented 6 years ago 
Ok to close this as a hardware issue and make it a software issue if we decide to go that route?

Closing; a topic about the stepper variant has been opened in the Forum.