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Richard Tuohy

Digital light vanes help!

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Hi all

I have a few model c printers with the original mechanical vanes. I don't have a way of making tapes for their readers though so I use notches and the trim dials for changes.

However I just acquired a set of digital vanes with controller. I am thinking it might be possible to control these from a pc. The programming side of that is no problem. But I need to work out the protocol for the 25 pin plug that connects the vanes. Does anyone have a diagram for the digital controller or digital vanes that shows the pin wiring? Yes I could most likely work out what pins are being sent what with a multi meter or cro unless the data is too fleeting. Any help would be appreciated!



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You might want to talk to Tom at Film&Video Solutions in Maryland, he has built a new software suite and controller setup for his printers which would probably run your new valve setup.

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Hi Richard,

I’ve been working on a similar problem recently (trying to control a Bell & Howell Model C printer) but have been coming at it from a different direction. I wasn’t able to find enough information about the controller itself (pictured below) so I focused on finding a way to make program tapes. What type of tape readers / control modules do you have?


I’ve managed to make (and successfully load and run) RGB and FCC program tapes on the printer. Here’s a brief rundown of how things work.

Equipment wise the setup consists of:

  • A Santec GNT-4606 paper tape reader / punch found on eBay.
  • A USB to RS-232 adapter for connecting the punch to a Mac.
  • A freeware application called CoolTerm to send the compiled FCC and RGB data to the punch.

The process of compiling scene RBG and FCC values to be punched on tape is somewhat laborious at the moment. It requires a step of manual translation from decimal to Bell & Howell’s “pseudo binary”. I’m working on a web app to take the manual labor out of the process and make it simpler to teach other people, but it's slow going.

If you’re interested I can go into greater detail and share the info I use to convert RGB and frame cue values into data the reader can understand.

I’ll also echo Robert’s suggestion to contact Tom at Film&Video Solutions. Finding a scan of the B&H tape specs on their site was key to figuring out how to get the machine I’ve been working with going.




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I know next to nothing about this sort of stuff, but it occurs to me that current microcontroller technology ought to Mae it relatively straightforward to go directly from computer software, via USB, to control the light valves. Doable?



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It ought to be straightforward, or at least I thought it would be when I started down this road. There's not much information out there about how the various control systems interact with the printers though. In my case the easier problem to overcome was the lack of a tape punch.


From what I can tell about the micro controller setup Video&Film solutions built, they've replaced the need for paper tapes but the control module still tells the machine what to do. Replacing the control module altogether would be ideal, but would require more information about the printer/controller theory of operation, and some real software development skills.


If anyone manages to do that I'd love to hear more about it. I know of at least a couple other model C printers out there that could use upgrades.

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Greetings Robert, Beau and Phil,

thanks for the tip regarding Tom at Film and Video. I will endeavor to make contact.

Beau, the controller you depict is indeed the one I have. So it seems you have found a way to controll as tape writer via its Rs232 port and a pc. Groovy. Sadly I don't have a writer at all. But it would be helpful to learn something from you about coding strips of tape. Perhaps I can punch the tape directly with a small whole punch and manually write the cues that way.

One thing I was contemplating was opening up the head of the tape reader and accessing the hole reading switches directly. But the tape reader head in the digital version doesn't seem to involve pins and switches. Is that correct or are they just retracted I wonder. Perhaps it uses leds and sensors. If it were simply pins and microswitches then it would be easy enough to control them via a series of relays from a usb controller.

I tested a few of the pins of the 25 pin plug at the back of the controller and there seems to be a mix of voltages there - some as high as 24v and some around 7 (I assume a TTL voltage). The probe ended up shorting a few things out and I blew a fuse so I think I will try to avoid that approach for the time being.

So anyway Beau, if you were able to tell me about the tapes, that would be interesting.

all the best,


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I considered manually punching tapes as well. When looking for tools I came across this paper-tape repair kit that looked promising, but I wasn’t able to find one (or anything similar) for sale. Looking back on it now I think the process of punching tapes manually would be too tedious. You’d also have to find tape with pre-punched transport holes.

You’re right: the digital controller uses LEDs and sensors to read the tape instead of pins like the electromechanical one does. It has more memory too so it reads the tape all at once instead of progressing through it one scene at a time.

I have a PDF of misc. Model C schematics that I’ll DM you a link to because it may contain some useful info for your original micro controller idea. Page 8 shows signal flows from between the reader, light vanes, and fader assembly.

I highly recommend keeping an eye on eBay for a GNT, Facit, or DSI punch / reader. The one I found was ~$150 USD plus shipping. WNC Supply in Arizona sells supplies and readers, but theirs are quite expensive.

I’ll DM you a link to download the resources I’ve been putting together for people who’d like to use the Model C here in Vancouver. Here’s a rundown of the files I’m talking about for anyone else who might be interested:


This file illustrates the anatomy of RBG, FCC and composite tapes. It includes blank templates for practicing how to fill in and read data from tapes. Note: I haven’t been able to get the controller above to read composite tapes successfully.


This is a blank form for filling out scene frame cue and printer light values when timing a print.

Bell & Howell punch tape conversion.xlsx

This spreadsheet shows the translations for RGB and FCC values from decimal to hexadecimal for punching. An example: to punch one space (just a transport hole) you send the hex value “00” to the punch. A printer light value of 25 = the hex value A4. So a string for a scene that is “normal” tape 25-25-25 = 00A4A4A4. Hopefully this will male more sense once you look at everything.


A compilation of strings that will punch out alphanumeric characters. Handy if you want to put your name on a tape, label it as “RGB” or “FCC” to reduce confusion in the future, etc.

Example report and data compiled

This is an example timing report and compiled data for a short "cinex test strip" that will print 3 feet and 30 frames in 10 frame increments at different light values for gauging exposure. I don't have a colour analyzer so this is the next best thing. I still need to make versions for colour printing. I can mail you the tapes for this to mess around with loading and running the program if you DM me your address.

Punch Tape vs. Bell & Howell tape comparison.xlsx

If you really want to geek out and understand how Bell & Howells "pseudo binary" is different, and what's up with the tapes being oriented differently than ordinary data tapes.

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HI Beau,

thanks for the info! I know that model C in Vancouver of which you speak. At the Cineworks Anex (the printer is of interest to the people at the Iris collective there). I spend a number of hours setting that printer up a year or so ago. They had a 35mm model C as well. I suggested at the time that they take the manual light vanes out of the 35 and put them in the 16 instead of the digital as with the manual vanes and controller you can easily rig up RF or notch cuing where you just turn the trim dials.

Please do send me those resources you mentioned.

many thanks!


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That’s the one. I was introduced to it during a workshop back in November and have been mildly obsessed with it ever since.

I sent you a Dropbox link to those files in a direct message. Let me know if you have any trouble retrieving them.

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