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Unread 28-07-2015, 01:25
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Re: Stepper Motors

Quote:
Originally Posted by JamesTerm View Post
So I'm curious how good of a fit these stepper motors would be in terms of wiring.
Well if we used standard 1.8 or 0.9 degree NEMA23 steppers like a RepRap with 1.2-1.4A per phase at around 3.5 to 4.2Ohms.
We could use the same Allegro Semiconductor A4988 drivers as the RepRap RAMPS 1.4.
That would get a STEP+DIR interface to the stepper motor for a 5V TTL signal level and take the motor power from either the battery directly or some DC/DC conversion.

An Arduino can obviously control this with a RAMPS 1.4 board on a RepRap 3D printer with several steppers per MEGA2560 so there' s no reason someone couldn't hack up either an Atmel based stepper controller or just use the digital I/O.

The carrier board based A4988 drivers can often be found for the $4-$8 range each.
If you look around you can find a cheap Arduino in the $5 range.
Even if you forked over for the whole RAMPS 1.4 board with the Arduino you can get that whole package for around $75 from SainSmart.
You may also want to get some small aluminum heatsinks for the A4988 they can overheat near stall.

So one could create some custom RAMPS 1.4+Arduino MEGA2560 firmware and have a bunch of these steppers running from a RoboRio with that as a coprocessor drawing power from the robot PDP breakers. Seems like $75 + $10-$20 a stepper motor. Cost wise it's easily comparable to cost of a Talon and a CIM or a bunch of hobby servos. Course this has the issue of how to integrate the field safety shutoffs, however I can see quite a few ways to make that work.

Speaking purely as a matter of possible - not as a matter of FRC legal.

Last edited by techhelpbb : 28-07-2015 at 01:40.
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