OK, I understand how stepper motors work, and how microstepping works.
But, I can’t figure out what the “W” is supposed to stand for in the “Excitation Mode” terminology:
Microstep Resolution Excitation Mode
Full Step 2 Phase
Half Step 1-2 Phase
Quarter Step W1-2 Phase
Eighth Step 2W1-2 Phase
Sixteenth Step 4W1-2 Phase
Winding ?
W=Wave (Drive) mode.
Ahh… that makes sense.
I looked on every data sheet I could find, and none of them defined that terminology before they used it.
Honestly: My IIRC failed me on this one, and ended up digging through my old notes. My work on steppers is only occasional, and usually involves only twisting the wires in a like kind replacement. Most of the “knowledge” is held within our AB PLCs that I rarely need to modify.
Decades ago I picked up a used equatorial mount solar tracker. It had a 120VAC electric motor driving it, and I replaced it with a surplus stepper-driven worm-gear reducer, and a breadboarded stepper controller. When I dusted it off (literally), I hooked it up to a power supply and tested it, and it worked perfectly, but it had more vibration than I was comfortable with, so I decided to re-do the stepper driver from 1/2 step to 1/16 step. I needed to figure out the gear ratio and step frequency (since I didn’t keep any notes from the first time). Turns out that the worm-gear reducer is 100:1, and the final gear reduction on the mount is 60:1, giving a final reduction of 6,000:1, or 19,200,000 microsteps/revolution.
I’ve ordered driver boards from ebay and ICs from DigiKey (1.000MHZ crystal and a Divide-by-N counter (set to divide by 1,125)). It will be interesting to see if the 1/16 step is that much smoother than the 1/2 step I’m using now.
Sounds like there may be some overkill in resolution (19,200,000 microsteps/revolution) for a solar tracker. This could lead to more vibration/chatter depending on the hysteresis of the controller.
Another thought: Is the motor capable of 1/16 step… Some are, some are not.
Just a notion: Perhaps reducing the resolution may eliminate the problem. Go from 1/2 to 1; 1 to 1 1/2, etc., instead of the other way around.
Sometimes, “looser” control parameters are key to a system’s operability.
Good luck with your project!
The nice thing about the controller I bought is that they can be set to 1, 1/2, 1/4, 1/8, or 1/16 step with jumpers, so I can test different modes on-the-fly.
I’m going to put some lead weights on the camera/lens system, which should help damp out any vibration. With a 6,000:1 gear ratio, I figure the motor should have no problem turning 10 lbs!
Out of sheer nosiness, would you PM me a link for your controller?
Thanks.
So, I got one of the controllers in the mail the other day. This one is interesting - it implements a sine-wave interpolation between each microstep, resulting in 256 interpolated microsteps per full step. I breadboarded it, and connected it to the stepper motor, and the resulting motion is a smooth as anAndroid’s bottom.
It’s based on the TMC-2100 IC.
Here’s the one I bought.
Glad it worked out so well. The minimal cost blows my mind.
I received a 3-D printer for Xmass… Sooner or later, I may travel the same road you are on.
May your tracker always achieve the optimal angle toward the Sun!
Ooohh… 3D Printer!
Have fun with that toy!
And, yes - there is a ton of info on the web about using this particular driver with 3D printers.
Bumping this in the unlikely event that anyone cares -
The TMC-2100 board I bought drives the stepper motor so smoothly in “stealthchop” mode that I can’t detect any vibration at all - even using a screwdriver on the motor stuck in my ear, it is completely silent. My divide-by-n circuit also works great. I even put a switch in for Sidereal vs Solar tracking (not that it would really make andy difference, but what the heck).
Very interesting! Thanks for the update.