Sunday, October 28, 2007


New Stepper Driver... video

Can ya step to this? from Zach 'Iowa' Hoeken on Vimeo.

my camera died at the end, but i was basically done.

I love it! How fast can you make it go?
hmm... well with the code i have running, at its fastest, i'm sending a pulse every ~600 microseconds. its a 200 step motor in half-step mode.

400 steps * 600 microseconds = 0.24 seconds / revolution.

60 seconds / 0.24 seconds = 250 RPM.

its smooth, and fast... but can that be right? i did put it under load on my X axis, and it lost steps on the highest speed... so 750 or 900 microseconds might be a more realistic value.

still, with 900 its still 166 RPM.

do those equations check out?
Damn! :-(

Yeah, your calculations check out. I was hoping for more rpm's than that, though. 166 rpm = 2.77 rps which means that your board will push a threaded rod system x or y axis at around 2.5-3 mm/sec using a thread pitch of around 1 mm/turn which is about what you find at reasonable diameters of threaded rod.

I guess I'm just so focussed on using threaded rods that I'm in for a lot of disappointment.

Damned good piece of work all the same though, Zach. I was wondering when somebody was going to bite the bullet and use the full 297/298 chipset for running steppers rather than just the 298. The 297 makes thing a hell of a lot easier to do.
You should be able to go faster simply by increasing the power supply voltage up to the max for the 298. That is the main reason for using a CC chopper.
sweet! yeah, i'm using a normal 12v power supply, but there is no reason you couldnt use a 24v or 36v in place of the 12v.

i'll have to give it a shot as soon as i can find an inexpensive power supply like that.
Is that 600uS per pulse per motor? as in can you get both motors at that speed or does it slow to half speed for a diagonal?
I just took a look at the RRRF store and three boards will cost more in shipping, customs and duty (I'm in Canada) than the boards themselves. So I'd like to take a shot at breadboarding one first. Can you make the schematic for this and your other boards available for download, Zach?


if you go to the documentation page for the board, there are links where you can download the files for it... included is a PDF of the schematic.


if you see my more recent posting, i managed to get non-blocking stepping going, so i should be able to drive them all at full speed, independently!!!
if you go to the documentation page for the board

Where do I find that page? I've been all over the RepRap documentation pages and all I can find are links to the v1.2 stepper controller which is (rather confusingly) older than your v1.0 controller.

I checked your own posts for links to documentation but didn't find any either.
Okay, I finally found it. I went to the board's entry in the RRRF store, clicked on the 'More info' link and finally got to the board's docs. (Shouldn't this page be directly accessible from the RepRap 'Documentation' page?)

That page talked about getting the files from SourceForge. The link on that page was broken but I found another reference to the SourceForge page elsewhere on the RepRap site and have now downloaded the files.
oops! i guess i didnt provide the link. here it is:
yeah, the sourceforge link was broken. now fixed.

i havent linked it from the main documentation area yet since its still a 'prototype board'.

i've definitely tested it quite a bit, and it works well, but it just doesn't have software written for it yet. i'm working on that now.
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