Using an electronic switch to select a stepper motor
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I'm considering my options for how to wire up my next printer. I've previously used 3 leadscrews driven by a timing belt and a single stepper, but the cost for this setup is very close to three screws driven directly by three steppers.
My levelling technique for the belt involved detaching the belt, and turning each screw by hand.
For the steppers, I intend to wire in a switch so I can turn off the idle current to one motor at a time.
What I was wondering was if there was a way to do this via some kind switch controlled by a regular Duet2 wifi board?
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but why would you not want to drive each motor by a stepper.
you gain so much more. the levelling can be automated.
https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors
just wire up an additional stepper
https://duet3d.dozuki.com/Guide/Connecting+External+Drivers/22 -
@Veti for a number of reasons. First off you need an expansion board, which adds costs. Second; I don't really subscribe to auto-levelling. It's simply too unreliable with glass and PVA, which is the cheapest and simplest adhesion method I've come across. Third; manual levelling only needs to be done once in a blue moon with a solid enough printer, and minor adjustments with the method I've described above are very easy.
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@MortarArt said in Using an electronic switch to select a stepper motor:
It's simply too unreliable with glass and PVA
this will work
https://www.thingiverse.com/thing:3303618
its cheap and reliable and has a high accuracy. -
@MortarArt said in Using an electronic switch to select a stepper motor:
manual levelling only needs to be done once
This is not true if You use separate motor for each Z - also connected to one stepper driver.
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Why won't it be repeatable?
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@Veti said in Using an electronic switch to select a stepper motor:
@MortarArt said in Using an electronic switch to select a stepper motor:
It's simply too unreliable with glass and PVA
this will work
https://www.thingiverse.com/thing:3303618
its cheap and reliable and has a high accuracy.This is off topic. I don't want ABL. My question was simple.
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@MortarArt said in Using an electronic switch to select a stepper motor:
Why won't it be repeatable?
Because when the motor is de-energized it will snap to the nearest full step which may be in different directions for each motor.
I wouldn't want to disconnect the stepper motors while energized and M18 is per axis, not per motors.
https://duet3d.dozuki.com/Wiki/Gcode?revisionid=HEAD#Section_M18_Disable_all_stepper_motors
@MortarArt said in Using an electronic switch to select a stepper motor:
I don't really subscribe to auto-levelling.
Well that may be, but it does exist for this very reason.
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@MortarArt said in Using an electronic switch to select a stepper motor:
First off you need an expansion board, which adds costs.
you can find step sticks that accept 3.3v so you don't need the official expansion boards, but as detailed already you will need dedicated drivers for each motor to not loose the possition (and if you have the dedicated drivers there is no point in sharing the control signals, and not a requirement to use abl)
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@MortarArt, do you plan to connect three steppers in series to a single duet driver output?
In this case, you one to shut the current of one stepper of the three you just need to short it two coils, letting the current bypassing it.
There are issues with connecting/disconnecting coils under power but I think that shorting/unshorting one of the tree in series is safe and doesn't create voltage spikes(?). Others with more experience may comment.
Just make sure not to short all three steppers and the same time since it will short the Duet's output and may damager it.
You also want to run everything in 24V and limit the speed of your Z.
