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Author Topic: Low cost homebrew red LED light source for cyan tracks Ron Yost Master Film Handler Posts: 344 From: Paso Robles, CA Registered: Aug 2003 posted 01-05-2005 10:42 AM                     Ha ha, Richard. I tried that with one of my 16mm Eiki's and it did, indeed, sound very nice. I was surprised. Never tried it on a full feature as my exotic (a bit of wood and duct tape) holder fell off after about 15 minutes. I doubt, but don't know, that a cheap diode would last for long?? Ron Yost  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 01-05-2005 10:47 AM                        quote: Ron Yost I doubt, but don't know, that a cheap diode would last for long?? Best advice: keep cool! Use an efficient heat sink (or even active cooling such as a water-cooled heat sink), and no more current than needed to get enough light output.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 01-05-2005 10:49 AM                        With all these good results being obtained from the home brew red LED light source, this really is the answer to the art house dilemma -- we must play a mix of old films as well as new cyan releases. Seems to me that if I have to choose between the sibilance distortion of shrill and splattering esses that you get when you play older prints "white light optimized" on red light readers, and the slightly better channel separation you get switching to reverse scan readers, I will choose white light playback any time and to hell with a tad better channel separation. What good is great channel separation if the soundtrack sounds like someone scrapping their fingernails across a blackboard? As stated above, switching back and forth between the two different types of pickups is out of the question. But being able to simply switch out a red light exciter to a white light exciter would be a workable solution. The ultimate solution would be to get a reverse scan reader that can be excited by two different light sources, perhaps with dual LED array -- one that contains both red and white LEDs. This would be the best of both worlds -- correct illumination of cyan tracks and correct illumination for prints optimized for white light "excitation."  |  IP: Logged Clive Carmock Film Handler Posts: 24 From: Morden, Surrey, UK Registered: Dec 2004 posted 01-05-2005 03:04 PM                     Hi Richard - a laser pointer in a TK35 - now that sounds a good idea! I wonder if you can drop me an email to put me in touch with the TK owner? I am keen to get a new aperture plate for mine if I can find a source. Regards Clive  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 01-05-2005 03:43 PM                     Wittner kinotechnik should have the plates...I'll look for the print out on the laser set up.  |  IP: Logged Edward Jurich Master Film Handler Posts: 305 From: Las Vegas USA Registered: Jul 2003 posted 01-05-2005 04:13 PM                     quote: Peter Mork Question - will a short reverse shot of 12v DC kill an LED that easily? Applying 12 volts directly to a LED can burn it out without a current limit resistor in series, depending on the current rating of the LED.  |  IP: Logged Bill Enos Film God Posts: 2081 From: Richmond, Virginia, USA Registered: Apr 2000 posted 01-05-2005 06:11 PM                     Our home builts have been performing excellently since 3 December. Added benefits are no readjustments due to filaments changing position, no short dip in sound on changeover, sound seems brighter than before, may be my imagination, but others have noticed too, changed equalization, red light has more eye appeal than dull white. The decrease in power consumption will probably not be detectable on the electric bill though. Overall this has been one of the easier and least expensive improvements we've made. Initially we had planned for this to be a temporary fix, to be in place for a year or so, but it has worked so well it may turn out to be permanent.  |  IP: Logged Jeff Rodenkirch Film Handler Posts: 3 From: Tucson, AZ, USA Registered: Jan 2005 posted 01-13-2005 11:28 AM                        I built one of these up using thermal RTV to glue a small heatsink to the back - It runs at 350ma and only gets slightly warm. At full output though it's about 4-6 dB short of driving a Dolby cp-55 to required level from a Simplex sound head. Does anyone know of a mod for the cat. 240 to get a bit more gain? I am a recording studio tech so modifying gear is second nature to me. The chain I work for (Grand Cinemas) is intermediate-market so $1k+ a pop for a reverse scan reader is not feasable for all of our screens. For those interested I've got light output vs. signal for the Lumiled. I can't measure the light directly so I went by supply current to the LED, you can figure the rest out from the data sheets. Output is measured at the test points of a cat. 240 with an Audio Precision Portable One using the cat. 69T Dolby test tone film cat. LED Current Level at cat. 240 test point -------------------------------------------- 350 ma 0 dB 325 ma -1.0 dB 300 ma -1.3 dB 275 ma -1.8 dB 250 ma -2.8 dB 225 ma -3.6 dB 200 ma -4.5 dB 175 ma -5.5 dB 150 ma -6.9 dB Jeff p.s. this is my first post. Thanks you guys for being around - Film-Tech.com has made my transistion into cinema much easier!  |  IP: Logged Alejandro Lopez Film Handler Posts: 22 From: Santiago de Compostela (A Coruña) Spain Registered: Nov 2004 posted 01-13-2005 04:24 PM                     Hi: Using a laser point on a TK35 it´s a correct. TK35 projectors have a macrooptic sound reader as opposite to most projectors (microoptic). It´s not a reverse scan but it´s good. But you´ll have to isolate the laser pointer from the projector cast as most laser pointers have the positive to chassis in oposition to projectors (negative to chassis) and it could shortcut the laser or at least make it long for a shorter time. 3- 4,5 volts DC is a good voltage for them. As for the TK35, is it quiet (silent) running compared to other 35mm portables or pedestal projectors? I´ve just won an auction on Ebay for one and I´d like to know this. I have the picture with the laser pointer on the TK35 and the e-mail addresses of the guys that do modifications on TK35´s on Germany, such as laser readers, halogen lamps, 1.800 meters (6.000 feet) reel arms, etc. E-mail me if you want. Alejandro.  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 05-27-2005 03:10 PM                     Here is a red LED that All Electronics has just started selling: LED-109 It can take up to 700 ma with a heat sink, and puts out up to 1 watt. The LED is mounted on a small round piece of metal, about the size of a nickle. It is $8.00 (plus shipping).  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 05-27-2005 07:52 PM                     Hmm. It starts saying quote: 1 WATT RED ULTRA-ULTRA BRIGHT LED and then goes on to say: quote: Cree XLamp(TM) 7090WRD. Extremely high-brightness white LED, capable of operating at 1 Watt and above. White or red? --jhawk  |  IP: Logged Frank Jerkic Film Handler Posts: 77 From: Ayr Queensland Australia Registered: May 2004 posted 05-27-2005 08:03 PM                        This sounds confusing the red has changed to white? Cree XLamp™ 7090WRD. Extremely high-brightness white LED, capable of operating at 1 Watt and above. Long-life, solid-state, low-voltage and current light, ideal for architectural, landscaping, advertising and entertainment applications.  |  IP: Logged Lindsay Morris Expert Film Handler Posts: 233 From: Darlington, WA, Australia Registered: Sep 2002 posted 05-28-2005 02:25 AM                     Cree lamp is only white and not a very high output one at that. The data sheet suggests around 44 lm which in comparison to the new Luxeon Star III type LXHL-LD3C which boasts 140 lm and that is the RED one running at 350mA. As Lumileds are in Silicon Valley USA folk should be able to get their hands on these quite readily... have a bit of a browse around the website Lumileds.com. There was a very good supplier of Lumileds here in Perth West Australia but I think they have closed up shop so will have to go ask the Lumiled website who handles their stuff now over here as the LXHL-LD3C looks like it will do the red reader trick quite easily. An earlier version of their led I was playing about with almost gave me dolby level from a cyan tone loop and that led was only rated at around 30 lm. This new one seems like it can do 4 times that amount of light for the same led current.  |  IP: Logged Henry Titchen Film Handler Posts: 31 From: Singleton, NSW, Australia Registered: May 2005 posted 05-28-2005 02:44 AM                     Lindsay, Oatley Electronics have a good range of LED's (Luxeon). They are located in Sydney and do mail order. I have had very good service from them over the years. Their web site is: Oatley Electronics LED page Henry. NSW Australia.  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 05-28-2005 07:55 AM                     If you bothered to read the information, the LED is available in several colors, RED and WHITE are just two of them. The LED this thread was started with put out 55 lumens max. The RED LED that I posted information about can also put out 55 lumens. I posted this info as an easy source to get the same sort of LED that the thread was based on.  |  IP: Logged

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