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Author Topic: Low cost homebrew red LED light source for cyan tracks Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 10-11-2004 02:04 AM                        For what it's worth, Bill was kind enough to send me a few dozen feet of cyan-track film. We tried it tonight on a Western Electric (700A - universal base) soundhead with white-light exciter. I had to turn up the sound from 6.5 to 8ish to get "normal" level, but I was encouraged that we actually got intelligible sound from the cyan track. I'm sure that the s/n wasn't so hot, however. The home-made Jaxlight will be tested later in the week....  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 10-17-2004 03:52 PM                     Hello!, I definitely must try this with lumiled led's. I can get them her but i must send special order to get it, does it some other led's can be used??? What is difference in normal film when you using normal exciter light and red light from lumiled led's? Another problem is that i don't have any cyan film... does anybody could send me a few meters (feet??) I also think this is great stuff because here where i live , red reader coast a lot and we can afoard it likely.... Jeff - Great stuff, please can you tell me exact type of led's that you using, thanks!  |  IP: Logged Bill Enos Film God Posts: 2081 From: Richmond, Virginia, USA Registered: Apr 2000 posted 10-18-2004 12:04 AM                     We tested 2 days ago using a preamp. We spliced in a preamp and ran cyan and silver tracks extensively with the red led and got good results. If you're not rolling in cash or have equipment that nobody makes replacement readers for this seems to be the answer.  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 10-19-2004 02:14 PM                     Did you tested it with stereo readers??? What type of led did you used ?? Are there any difference in sound quality between red led and exciter lamp when you playing normal film?? Also did you notice any changes in channel difference if you try that with stereo reader?? Thanks for help, i also preparing for led reader because they tell me that from Christmas all films gonna be cyan.  |  IP: Logged Bill Enos Film God Posts: 2081 From: Richmond, Virginia, USA Registered: Apr 2000 posted 10-20-2004 12:34 AM                     We tested with stereo pick-ups using the Luxeon Star red led operating at 285 ma. On silver tracks we couldn't tell any difference between exciter and led. Channel separation etc. was normal  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 10-20-2004 03:41 PM                     Glead to hear that sound is ok! Can you just tell me what is type of led that you use?? P.S. Does somebody can send me a cople feet of cyan film, so i can try this with my measuring equipment?  |  IP: Logged Peter Mork Expert Film Handler Posts: 181 From: Newton, MA, USA Registered: Jun 2002 posted 10-20-2004 06:20 PM                     I have built my own copy of Jeff's gizmo with a couple of changes. Haven't tested it extensively but it does light. I'll post a photo soon. There are many different Lumiled Luxeon Stars available. The one I used was LXHL-MD1D (which I got from Future Electronics at a measly $6.25 per). It is rated at 44 lumens - less than Jeff's 55, which I couldn't find, but should do nicely. [ 10-21-2004, 01:35 AM: Message edited by: Peter Mork ]  |  IP: Logged Bill Enos Film God Posts: 2081 From: Richmond, Virginia, USA Registered: Apr 2000 posted 10-21-2004 12:47 AM                     I used the same one as Peter, it will probably go into operation Monday.  |  IP: Logged Peter Mork Expert Film Handler Posts: 181 From: Newton, MA, USA Registered: Jun 2002 posted 10-22-2004 01:36 AM                     Here is my version of the light: I decided I wanted it to be self-contained and removable, so I wired the resistor directly to the LED, positioning it behind the disc. Then I smooshed some epoxy putty around the wires and tweaked the position of the LED until it gave the best output with a test film. Once hardened, it can be removed from the holder like any other lamp. (I left out the capacitor - stuck it in the feed line instead.)  |  IP: Logged Jeff Stricker Master Film Handler Posts: 481 From: Calumet, Mi USA Registered: Nov 1999 posted 10-22-2004 06:55 AM                     Looks great, Peter. I like the idea of having the resisor right at the LED. You can turn that one around and have a tungsten exciter if you desire.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 10-22-2004 11:07 AM                        Necessity is the mother of invention! Let us know if you are getting enough light, and how the output holds up with time. How hot does the LED feel during operation? Any issues of noise or microphonics?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 10-22-2004 06:54 PM                     285 mills is quite a bit of current for an LED so be sure to heat sink it VERY well or they will fade out fast!! Dolbys LED typically runs at much lower current in the later generation of readers with faster optics. Mark  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 10-22-2004 08:50 PM                     Ah but did you all notice that his RCA exciter holder now not only has a red LED but a tungsten exciter lamp for silvered tracks. Did you measure and notice any difference in focus between red and white light? Steve  |  IP: Logged Peter Mork Expert Film Handler Posts: 181 From: Newton, MA, USA Registered: Jun 2002 posted 10-23-2004 12:22 AM                     In the mono head I'm running it in, there's a small drop in output level with the LED, which I boosted at the amp. Sonically it's about the same to my ears as the incandescent. Ran it all day and it was perfect. The LED barely gets warm at all - the resistor does get too hot to grab onto, but seems far enough apart from the LED to not affect it. I'm happy. I have no cyan film to check it with, so how well that works I can't comment on.  |  IP: Logged Jeff Stricker Master Film Handler Posts: 481 From: Calumet, Mi USA Registered: Nov 1999 posted 10-23-2004 07:08 AM                     The Luxeon star (from the specs that the supplier gave me)can be operated at 200 mA without a heat sink and up to 300 mA with additional heat sinking. Life was quoted at 100,000 hours if operated within those guidelines. I comes on a metal substrate about the size of a quarter which provides quite a bit of heat disapation. BTW, I did notice that the focus setting needed to be "tweeked" when going from tungsten to red LED. I'm not suprised since I doubt the slit lens has any special coating to correct for chromatic aberation (I think that's the term for different wavelengths focusing slightly differently??).  |  IP: Logged

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