Quote:
Originally Posted by jman4747
That assumes we use the same rule that only specific controllers are allowed.
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How else would you implement the field safety features such that the stepper can not be moved while not enabled?
Quote:
Originally Posted by jman4747
A 12v to 24v step up converter isn't necessarily all that hard to find. I Don't however know about the required current capacity for a typical size stepper you could likely see on an FRC robot.
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Yes you can certainly boost voltage like FIRST did with the cRIO.
Something like
this would do it.
Course at 24V@3A you are just scratching the surface of the power requirements for a single stepper.
As an inductive load your switching DC-DC converter will need to be slightly overrated.
A A4988 for example can handle 1A coils with minimal heatsinking, 2A if you fully heatsink and force air cool. So if your RAMPS 1.4 PCB is configured like a Prusa I3 then you have: X, Y, Z split to 2 stepper drivers, extruder single stepper. Assuming the coils are all in parallel it's easy to pull 1.4A or more to each stepper while moving full steps if the current limit set on the A4988 allows it. It is quite possible the maximum torque will limit below 200oz-in at the lowest RPM, more over even below 100oz-in with some stepping motors. This assumes of course that the voltage of the stepper is such that the robot battery voltage is sufficient to move it the full stepping and micro-stepping modes. So the voltage of the stepping motor should be below 12V to come off a FIRST style battery. (This is safe because this A4988 driver is a current limited chopper driver: set the current limit wrong smoke the stepper motor AKA safe unless you do it wrong.)
To put this in perspective: a <12V NEMA23 stepper with this A4988 on a 12V battery is going to be about the force of a general case hobby servo.
A RepRap generally needs a fraction of this force to move the mechanics if built properly.