Blog for the RepRap project at www.reprap.org - a project to create an open-source self-copying 3D printer. To get all the early posts on this blog with all the images as a single PDF visit this page.
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Friday, December 05, 2008
Building a printable stepper for a next generation Reprap
In which your narrator gets down to cases in the quest to design and build a more or less printable stepper motor... do you want to read more?
Thanks, eD. A wow from you is something I really treasure! :-)
It gets lots better than this, though. While I was getting my head around this kind of motor I realised that UNLIKE regular stepper motors it doesn't need polarity control on the windings. As a result you can run the one I'm designing with three standard power transistors like the TIP110 that everybody is familiar with. While the TIP110 will handle 2 amps/winding, way back when I bought a sack full of BD681. Those are rated at 4 amps. :-D
I've been corresponding with Chris and he gets the same impression vis a vis not needing controller chips.
I'm pretty sure that I've got half a dozen lying around here somewhere. I toyed with the notion of making a high amperage stepper controller from discrete parts at one point and bought most of the parts. :-)
Yup, I remembered correctly. Got 6 MOSFETS. HUFA76419P3's rated for 20 amps and 60 volts. That's serious overkill, but what the hell. I've had 'em laying around for years now.
Wow, this is one of the final barriers towards pure self-manufacture... nice one Forrest, and good luck
ReplyDeleteThanks, eD. A wow from you is something I really treasure! :-)
ReplyDeleteIt gets lots better than this, though. While I was getting my head around this kind of motor I realised that UNLIKE regular stepper motors it doesn't need polarity control on the windings. As a result you can run the one I'm designing with three standard power transistors like the TIP110 that everybody is familiar with. While the TIP110 will handle 2 amps/winding, way back when I bought a sack full of BD681. Those are rated at 4 amps. :-D
I've been corresponding with Chris and he gets the same impression vis a vis not needing controller chips.
If this thing works it's goodbye L698N. :-)
Much better to use MOSFETS as they don't waste 2V and get hot.
ReplyDeleteI'm pretty sure that I've got half a dozen lying around here somewhere. I toyed with the notion of making a high amperage stepper controller from discrete parts at one point and bought most of the parts. :-)
ReplyDeleteYup, I remembered correctly. Got 6 MOSFETS. HUFA76419P3's rated for 20 amps and 60 volts. That's serious overkill, but what the hell. I've had 'em laying around for years now.
ReplyDeleteThanks for the heads up, Nop! :-)
Yes they should do the job without the need for heatsinks.
ReplyDeleteIt is a good idea to put a resistor in series with the gate, say 1K :-
It limits the current the PIC has to provide when charging the gate capacitance.
It slows down the switching slightly. You don't want really fast edges when driving a stepper as it just gives more switching noise.
It can also reduce a tendency to oscillate when the gate is driven with a low impedance.
Of course don't forget the back EMF diode.
LOL! A sketch would be useful. I am an AMATEUR, you know. :-P
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteAh! As they say, a pic is worth a thousand words. :-D
ReplyDeleteThanks!