Step pulse polarity settings w/ common firmware?
Posted by JamesNewton
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Step pulse polarity settings w/ common firmware? May 17, 2013 06:18PM |
Short question: Is there a way to change the polarity of the step pulse from normally off, pulse on briefly, to normally on, pulse off briefly?
Background: We are getting ready to add an new stepper driver to the open source Linistepper brand that will be lower cost, higher power. This is potentially useful to 3d printer people who want to make big 3d printers with NEMA 23 motors and MORE POWER!
When you get t bigger motors, with big drivers you need to control motor heating. If you leave them at full power while they are NOT moving, they fry. So typical high end drivers have a current reduction mode that automatically reduces the current when it hasn't seen a step pulse in a while and quickly raises the power when the pulses start up again.
Simple versions of this current reduction on hold circuit will fail if the polarity of the step pulses is not as expected. It's generally very easy to change polarity in CNC software (MACH3, EMC2, etc...) but I'm not finding a way to do it in Merlin, Sprinter, Teacup, etc... We would like to see if we can reduce the cost by going with a simple version or do we have to include a more complex circuit that can work with both polarities.
I'm hoping that the community here can tell me if I'm missing something, or if this is another reason why everyone is locked into those closed source, little, pololu drivers.
By the way, our big open source THB6064AH driver already does work with the 3D printers and will drive 200 watts (4 amps / 50 volts) into a NEMA 23 or 34 motor. But it costs $35 in kit form. This new driver kit promises to be much less expensive, and almost as powerful.
[www.linistepper.com] Open source stepper motor drivers.
Background: We are getting ready to add an new stepper driver to the open source Linistepper brand that will be lower cost, higher power. This is potentially useful to 3d printer people who want to make big 3d printers with NEMA 23 motors and MORE POWER!
When you get t bigger motors, with big drivers you need to control motor heating. If you leave them at full power while they are NOT moving, they fry. So typical high end drivers have a current reduction mode that automatically reduces the current when it hasn't seen a step pulse in a while and quickly raises the power when the pulses start up again.
Simple versions of this current reduction on hold circuit will fail if the polarity of the step pulses is not as expected. It's generally very easy to change polarity in CNC software (MACH3, EMC2, etc...) but I'm not finding a way to do it in Merlin, Sprinter, Teacup, etc... We would like to see if we can reduce the cost by going with a simple version or do we have to include a more complex circuit that can work with both polarities.
I'm hoping that the community here can tell me if I'm missing something, or if this is another reason why everyone is locked into those closed source, little, pololu drivers.
By the way, our big open source THB6064AH driver already does work with the 3D printers and will drive 200 watts (4 amps / 50 volts) into a NEMA 23 or 34 motor. But it costs $35 in kit form. This new driver kit promises to be much less expensive, and almost as powerful.
[www.linistepper.com] Open source stepper motor drivers.
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