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Author
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Topic: I'm building a box to lock projectors to 24fps
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Pete Richards
Master Film Handler
Posts: 302
From: Australia
Registered: Sep 2010
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posted March 08, 2015 06:51 PM
G'day Campers,
I've been working on locking my various projectors to 25fps for telecine purposes, but have noticed that since Pedro isn't making motor controllers any more, there is some interest in being able to sync projectors to DVD or CD soundtracks for higher quality audio playback.
The project I am creating could be modified to work at 24fps, would anyone be interested in such a unit if I made a run of them?
It would take a bit of work to set it all up, but I'd be willing to do it if there was demand.
I experimented with different methods, but as there are so many projectors out there, and people don't want to hack them up too much, I came up with the least intrusive method I could think of.
Basically the box would work on any projector that has a manual speed control knob. A sensor is fitted inside the projector to monitor the shutter speed, and the motor speed is adjusted to keep the shutter locked at a precise rate. The box drives a motorised pot, which is mechanically attached to the speed control knob on your projector. If the speed needs to adjust slightly up or down to maintain sync, the pot drives the speed control knob appropriately.
When lock is achieved, an LED is lit, you may need to run a slightly longer leader to let the projector get 'in the zone' when firing it up for the first time, and it would be adviseable to have good belts and the projector running as smoothly as possible, so that only minor adjustments are required.
Anyway, that is the gist of it, if there is any interest, let me know and I will make a prototype for someone to test. Again, it will only work if your projector has a speed control knob (or a dc motor, as you could power it from an external PWM controller that had a speed control knob), and you would need to fit an interrupt sensor inside the projector.
As for costs, I am not sure at this stage, I don't know how much the Pedro boxes were, but this should be considerably cheaper. It would consist of a PIC controller chip, PC board, a handful of components (transistors, capacitors etc.) and the motorised pot.
Cheers
-Peter
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Andrew Woodcock
Film God
Posts: 7477
From: Manchester Uk
Registered: Aug 2012
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posted March 08, 2015 06:58 PM
If full fitting instructions are given out with your products Pete, you know you can count me in.
I would love to be able to screen optical prints on my Beaulieu, and though not ideal setting up a separate audio system each time i want to screen one of these prints, it would at least offer me a true non damaging solution to this as well as giving me an option for some of the fantastic mute prints out there.
Finally, re recording poor soundtrack prints is a big part of the hobby to me, so again, anything that makes this easier and less time consuming for me on this front, is music to my ears Pete!
For me personally, I would love a replica of the the best Pedro box. It works so well on many levels given the digital frame rate display and that of the projector that you can control etc etc.
The best of the Pedro boxes were not cheap, around 700 euros in total I think if you include the internal projector modifications, but to me, this is the only type of total solution for my personal needs for matching quickly digital sources to film for both recording and playback purposes.
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"C'mon Baggy..Get with the beat"
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted March 08, 2015 10:45 PM
Does Pedro have patents on his electronic box, and if so have they expired by now, so that his invention is now in the public domain? If they have, then it would be easy, I would think, to reverse engineer one.
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The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
Eumig S938 Stereo f1.0 Ektar
Panasonic PT-AE4000U digital pj
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