Back then...this is what we did...

[lasermaster1977]

I've been putzing around on and off from one project and thoughts on numerous others over these many months, never getting much of anything done except lots of CAD drawings of components and ideas. Its been harder to stay focused on any one thing, sorry to say.

But, good things (hopefully) come to those who wait.

One contemplative putzoid thought of mine over these past years was derived from looking and learning from those who've implemented lumia effects either in dedicated lumia projectors or stepper driven mulit-lumia/diffraction grating wheels, and comparing these to those we built into my first RYGB scanner/lumia/diffraction grating projector. They were made of easily available components, cheap to acquire and simple to build. They weren't fancy but they worked well. Effect wheels were moved into and out of beam paths manually, by pulling on strings running through tiny Teflon pulleys...truly.

Page 6, post #42 showed how a recent recreation of what I used back then... several (6) Synchron 110VAC slow speed motors (.5, 1 and 2rpm variants) to rotate either diffraction gratings via rim drive or lumia wheels mounted directly on the motor shafts. Back in the late 70's, Edmund Scientific sold these Synchron motors for $1 apiece. They were heavy and bulky, rock steady smooth. Back then I wished there had been a variable speed solution to these Synchron motors, no doubt there were but they didn't reveal themselves to me in a viable way.

I got gobs of "stuff" that I've acquired over recent years but never the time, or more succinctly the inclination to tinker.

Then recently, I saw on-line a miniature stepper driven lead-screw I wished I'd had the wherewithal and know how to use back in the day. We originally used some cheap-o lead-screws that were driven by DC motors with plastic gear reductions but they were growlingly loud.

This pulled into focus all the related ideas I've contemplated and considered for my "new" lumia and diffraction grating effects and whether to use them with the RGB scanner output beam(s) or with a separate, dedicated RGB LED outputs.

I used relatively big NEMA 23 hybrid stepper motors and H-bridge full and micro-stepping drivers on my DIY CNC machines going back to 2010. Only recently have I discovered how small some steppers have become.

Tonight I just tested using the 28PYJ-48 unipolar stepper with the ULN2003NAPC stepper driver as a "effects wheel motor and was blown away by how well it worked and how smooth it was. I did a quick (and easy) substitution of it on the rim drive mount in the page 6, post #42 and here are two photos of the result. (coming soon with a YT video link)

28PYJ Stepper Substituted, Rear and Side Views


On the rear view I've sketched out lines that show reduction of mount size, plus the mount could be made of thinner acrylic material in not thin aluminum.

The 28PYJ is a 32 steps-per-rev stepper driving a 64:1 geared output shaft yielding ~2048 steps per rotation and runs nicely off of 5VDC, plus it is dirt cheap, super small, and easily modified to a bipolar stepper and driven with the better DRV8825 and/or DRV8833 chips.

EDIT: YouTube link added
https://www.youtube.com/shorts/lV80VTjkQIE

This video shows a programmatic "relative" rotational speed of 5 within a range of 1 to 15 -17.

EDIT: I easily found many YouTube videos on this unipolar stepper. Several show how to isolate the center-tap common lead from both coils converting it to a bipolar stepper which can then be driven with the about same power and operating temperatures while achieving far higher torque. As it is, half-stepping the unipolar mode achieves 4096 steps per motor shaft revolution.

Also note that there are a number of different manufactures of the 29BYJ-48 in both 5V and 12V variants, but also with different manufacturers having varying amounts of gearing backlash, so just FYI. If just rotating effects discs is the objective at programmable speeds with fine control, forwards or backwards rotation this is pretty cool. Its position repeatability is not too shabby either and if coupled with Homing switches this can helpful in other types of stepper applications.

My photos showed a 50mm camera lens mount diffraction grating, which was readily available to me from my old projector parts. I would use rim drive with any round effects disc where additional speed reduction is desired and mount the effects wheel directly on the stepper output shaft when its slowest shaft speed suffices.

Finally, my preference from the start when using these "effects wheels" was to be able to position them in the scanner output path, or a dedicated lumia beam, single and/or double-ganged.
That's where I'm headed with this now I have what appears to be easily obtainable with today's programmable stepper "stuff".

EDIT: 10-11-25 Today I put the 28BYJ through its speeds of 1-17 rpm (gear box output shaft rotation) and confirmed a software speed value of "1" does result in a 1 rpm shaft rotation output. I ran further tests to calculate more accurately the effects disks rpm reduction with my rim drive setup, which is an additional 7.45:1. With a stepper shaft speed of 1 rpm, my ~2.5" effects wheel does one full rotation is 447 seconds.

Among my original lumia discs and sheets from my beginnings I did find one lumia disc I had made ~45 years ago whose diameter matches that of the rim-driven 50mm diffraction. The lumia disc's edge is V-beveled just under a 90 deg. angle so it has no 0-ring. I swapped in the lumia disc. It was a perfect fit and rotated smooth as silk. Here are some photos of this:



With a stepper shaft speed of 5rpm the lumia disc rotated at 5/7.45 rmp it looked great. I took some lumia videos using this setup and did a short YouTube test/demo video here: https://youtu.be/yxhl56Ak28c

[TheHermit]

Yes, the 28BYJ even with drivers are inexpensive and have been very popular within the Arduino & Raspberry Pi maker communities, having been included in their starter kits over several years.
If it's a small stepper you're after, check out these tiny li'l beasties. I've used similar ones on another project and was amazed at how much torque they have.
BTW, your video wouldn't play on Chrome.
Roj

[lasermaster1977]

Yes, the 28BYJ even with drivers are inexpensive and have been very popular within the Arduino & Raspberry Pi maker communities, having been included in their starter kits over several years.
If it's a small stepper you're after, check out these tiny li'l beasties. I've used similar ones on another project and was amazed at how much torque they have.
BTW, your video wouldn't play on Chrome.
Roj

Yup, mine came in an ELEGOO UNO Starter Kit I got 3-4 years ago. I ignored the little stepper thinking it would be kinda jerky in its movement...until I recently saw some YTs showing it in action. For me, its big selling point was it being a geared down 32-step-per-rev stepper by 64:1 yielding 20248 steps-per-rev using full steps or 4096 using half steps...and it being easily converted to bipolar driven.

Those is some tiny steppers alright!

Thanks for alerting me to my video link not working...I fixed it just now so it should work now.