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Author Topic: Low cost homebrew red LED light source for cyan tracks Jeff Stricker Master Film Handler Posts: 481 From: Calumet, Mi USA Registered: Nov 1999 posted 08-05-2004 06:42 AM                     David, I have not done either test yet. I plan to get another LED in a few weeks for the stereo sound head. Alas, I don't have any cyan track film yet.  |  IP: Logged Peter Mork Expert Film Handler Posts: 181 From: Newton, MA, USA Registered: Jun 2002 posted 08-30-2004 07:13 PM                     Jeffrey, I like this idea and would like to build one. I know how to sling a soldering iron but am not much of an electronics guy and can't really see from your photograph how to rig the resistors. Could you help me out here - maybe post a diagram? Thanks.  |  IP: Logged Jeff Stricker Master Film Handler Posts: 481 From: Calumet, Mi USA Registered: Nov 1999 posted 08-31-2004 07:01 AM                     Peter, Not sure how to post a diagram. But place the resistor in one of the wires that goes from the power supply to the LED. The other lead of the LED goes directly back to the power supply. If you wire the LED backwards, it will not light (since it is a diode and only conducts current one way). In that case, just turn the LED around and it will light. Jeff  |  IP: Logged Frank Jerkic Film Handler Posts: 77 From: Ayr Queensland Australia Registered: May 2004 posted 10-06-2004 05:28 AM                        Hey G'Day Jeff, You said that you planed to get another LED in a few weeks for the stereo sound head, have you got around to trying that out yet and what were the results as I would like to try it out on one of my century's Whats the correct name/description for the Red leds you use thanxs Frank  |  IP: Logged Jeff Stricker Master Film Handler Posts: 481 From: Calumet, Mi USA Registered: Nov 1999 posted 10-06-2004 07:00 AM                     G'day to you Frank. Well, I've been procrastinating some. My stereo soundhead is still running with a tungsten exciter lamp. (I see no reason why it won't wont work because I got a pretty evenly illuminated slit with the LED) I need to get off my backside and get a LED for it. Of course, if I ever get some cyan soundtrack film the need will arise very quickly. The manufacturer of the LED was Lumiled Luxeon Star. I can't remember the distributor I got it from now. I will see the fellow in November and get his name and particulars. Jeff  |  IP: Logged Paul Trimboli Master Film Handler Posts: 274 From: Perth Western Australia Registered: Dec 2002 posted 10-06-2004 08:21 AM                     Frank they are LUMILEDS and avaliable from most electronics shops in Australia now. I got some which I plan to fit to my soundhead. I know a friend of mine tried them on his stereo century soundhead with CYAN film track and it worked, although there was less level which he found was becuase the LEDs he got were the model down from the ones Jeff has used, I am not sure if he has tested it with the brighter ones yet.  |  IP: Logged Jeff Stricker Master Film Handler Posts: 481 From: Calumet, Mi USA Registered: Nov 1999 posted 10-06-2004 08:42 AM                     Paul, sure glad you had good results with your Century soundhead. My main purpose in conducting these experiments was to provide a low cost red LED cyan reader for people with home theater set ups and a limited budget (like myself! ).  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 10-06-2004 08:56 AM                        There is an ISO standard being developed for the spectral response of red readers: quote: ISO/DIS 20859 Cinematography - Spectral response of photographic audio reproducers for analog dye sound tracks on 35 mm film 2 Spectral response 2.1 The peak or maximum response of the combined audio reproducer light source, filter, and receptor shall be 660 nm + 20 nm / – 30 nm. 2.2 The integrated response of the unit to all wavelengths greater than 800 nm shall be less than 5% of the total integrated response measured from 400 nm to 800 nm. Contact Carl Girod at the SMPTE if you have any comment or suggestions for this draft ISO standard.  |  IP: Logged Edward Jurich Master Film Handler Posts: 305 From: Las Vegas USA Registered: Jul 2003 posted 10-06-2004 09:10 AM                     If you just replace the exciter lamp with a red light, isn't that the same as using a JAX light? I've worked with JAX light and I've installed red readers, the red reader sounds a lot better. Using an old cell with a red light does not produce as clean a high end as a red reader. Also, I've found in larger auditoriums that had to have the tubby lower mid-range EQ'd out with the old exciter/cell, still needed the EQ with the JAX light but not with a red reader. I replaced the JAX light with a red reader at the one installation and it sounded much better with the red reader.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 10-06-2004 11:36 AM                        Well, I am a tinkerer by heart and love the fact that Jeff has come up with a $10 solution that achieves his original goal quite beautifully, that of being able to play cyan tracks without having to shell out big bucks. The fact that it may not have the advantages of the improvement one can achieve with reverse scan matters not because that wasn't what he was aiming for. He just wanted a viable way to be able to play cyan and get the sound equal to what he has now with a convention white exciter and forward scan. When Dolby first came on the scene with the CP50, I was able to get my hands on a stereo cell and it wasn't long before I was whipping up my own stereo playback mimicking the CP50 with used stuff from the recording studio that is part of the performing art center here. I was lucky enough to get two Roger Mayer super-quiet preamps with parametric eq built right in, a used Dolby A studio noise reduction unit designed for tape recording, a consumer Dolby B n/r unit, a Sansui 4 channel decoding unit, a Revox 6 channel mixer, three studio 1/3rd octave eqs, a consumer 1 octave eq (for the surround which the even CP50 didn't have), and tad-da! Optical Stereo sound without having to spend what was a fortune (for us) for a new CP50. It was all used equipment and it sounded damn good for what it was. So now this tinkerer hears all this stuff bout bumps in uneven illumination of the 12 LEDs in Dolby's array and the disadvantages of a single point illumination of Jeff's incredible super bright red LED and me thinks, gee, I saw a variety of these novelty "light sculptures" that used very thin, very bright fiber optic strands to create the effect of hundreds of pin-points of light. They all come to a bundle that is placed next to a bright light source from which they fan out to make the light design. Point is, they are really THIN, probably no more than a millimeter or two in diameter. Me thinks this would be a perfect solution to the problem of uneven illumination between the LEDs in the 12x2 LED array. You could pack, I don't know, say 48 by 8 or even more of these fiber optic filaments into an array to evenly illuminate the entire soundtrack with virtually no unevenness or "bumps" and they would do better than a single point source of light with regard to noisy playback. Adding a bunch of fiberoptic strands to Jeff's Lumin LED Star unit would make the thing cost, what....$10, $20 more than his original $10 solution? I am surprised Dolby is sticking with trying to physically pack bulky LEDs together when fiber optics seems like it could be a really elegant solution to uneven illumination, or am I missing something? Oh, and PS, remember I said somewhere in this thread that we really needed an exciter which is capable of changing light sources from red to white with the flip of a switch so that we could easily accommodate both type of prints -- those optimized for white excitation and those optimized for red excitation, re: cross modulation? Well, fiber optics would do just that....you would just physically slide the fiber bundle on the light source end from a red LED to an ordinary white, high intensity 12v quartz lamp. I see Jeff is already on Google searching "fiber optic filaments"  |  IP: Logged Bill Enos Film God Posts: 2081 From: Richmond, Virginia, USA Registered: Apr 2000 posted 10-09-2004 04:00 PM                     We have built one of these things, it seems to work ok but will need a preamp before we'll know for sure--that will be tried next week. All the high dollar reverse scans as well as the Jaxlites need preamps as well. If it works, we will use it for about 6 months until a couple problems are resolved.  |  IP: Logged Jeff Stricker Master Film Handler Posts: 481 From: Calumet, Mi USA Registered: Nov 1999 posted 10-09-2004 05:46 PM                     Ah Frank, very interesting idea! That's got to motivate some of the experimenters for sure. Oh, Ed asked if using red bulb would work. That's the equivalent of a red filter in front of an incandescent lamp. The answer is it won't work. You are not increasing the amount of red light coming from the lamp by using a filter, you are just filtering off the other colors and letting the red pass. The end result using a cyan track won't sound any different than just the unfiltered bulb.  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 10-09-2004 07:02 PM                     I had the idea of removing one of the segment "light pipes" from an LED seven segment display, and using this to "spread out" the light, but have not had the time to try it.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 10-10-2004 10:00 AM                     Actually Kinoton has a low cost option that is a slide projector lamp nd a red dichroic filter available  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 10-10-2004 02:49 PM                       Regarding Kinoton, I may be wrong but I'm told the filters fade rather quickly leaving you in a pickle. Supposedly, Kinoton withdrew te product but I have not had a chance to track this report down.  |  IP: Logged

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