Frame-by-frame with a stepper motor

[Stan Jelavic]

Another one of my little projects. Used a Chinon projector, replaced the motor with a stepper and used one of my MSP430 controllers to precisely turn the projector cam one rotation at a time. For each rotation, the controller provides a trigger to the camera. What is the advantage of the setup you may ask. The short answer -- no trigger cct is required. The trigger cct can be a pain to setup and get it to run reliably. Additionally I will try to run the real time capture with the same setup. The first attempt at doing that failed due to the low stepper torque. A new more powerful motor might do the trick. Will keep you posted on the progress of that endeavor.
https://photos.app.goo.gl/CnTxv4bXJBfoPvaW8
https://github.com/vintagefilmograph...frame_by_frame

[David Brown]

Hey Stan, always interesting to see your projects!

Is the video showing a newer stepper motor? I would've suggested cleaning and lubricating. The old grease congeals and taxes the motor. Yours looks clean enough. I nearly took an old S8 I bought to the carwash, but instead just spent a lot of time cleaning and lubricating. It runs great now.

The video shows us that this is already running and I can hear the camera snapping. You hinted a while ago that Chinon would be a good candidate, though I can't remember why. Stepper motors "seem" to be smaller than other motors I remember inside projectors. So that should be easy to swapp out?

Anyway, I can't wait to see a capture.

[Stan Jelavic]

Good points David. I did dismantle the unit and cleaned it and lubricated it as much as possible. It runs reasonably well. I do have another larger stepper to see if it is faster than this one. This one in the video runs around 1 FPS. The larger stepper may be faster but obviously the camera exposure time gets added on top of the stepper time there will be a limit how fast this will go. I have not tried any capture because my canon reverse lens cannot get close enough to the gate and I do not feel like dismantling my Wolverine/Hawkeye setup to use the BUC02 camera. So this is just a feasibility test if the stepper can be precise enough for the frame by frame capture.

[Nantawat Kittiwarakul]

Very interesting!

Got an potentially interesting idea - how about using toothed belt & pulley with, say, 1:1 ratio? Using toothed belt means the drive ratio will always be constant. Therefore the trigger signal can be "programmed" into any angular position to get the optimal timing.

Then run the mechanism at constant speed (and as fast as the camera can handle). So the mechanism & the film itself would be in smooth, continuous motion with the exception only at the film gate where it would have to be intermittent.

Only if I'm not totally electronically idiot like this I'd have it done myself by now.

[Stan Jelavic]

That is definitely possible. One pulley can to attached to the cam and the other one to the motor. Then one rotation of the stepper pulley would correspond to one rotation of the cam pulley. With my tuning method I program the stepper so that one activation of the stepper results in one turn of the cam. The initial position is always retained for optimal timing for camera trigger which is generated by the controller itself. The issue with my method is that there is still some drift over time but I can go for a few thousand frames before the readjustment is made. At one FPS this translates into around 45 minutes of scan before a readjustment is done which is probably ok for some people.

[John W. Couvillon]

Using a projector as the transport mechanism is very workable. The stepper drives the main projector shaft which drives the projector "grabber" that moves the film one frame at a time. The wire you see on one of the gears holds the mechanics such that the take up reel is rotated with each grab. notice the use of a timing belt in lieu of a pully and belt. One revolution of the stepper moves one frame consistently. I am using a USB camera placed where the projector bulb was located, with the an LED lamp where the lens was. as setup, the camera sees the shinny side of the film. I'm not sure that are reversed hortizontally. This film has not been viewed since the 80's. How can I tell if the film is rolled up backwards on the reel?

[Stan Jelavic]

Cool setup John. I have a similar setup with the Chinon transport.

Regarding your question regarding the backwards film. If the film is indeed rolled up backwards then it will run backwards in time. If that is teh case just rewind it backwards again. Or maybe it was never rewound back. In that case just rewind it onto the feed reel.