Film-Tech Forum ARCHIVE: Sr sound Leds details.

This is topic Sr sound Leds details. in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Peter John Anthony. C (Member # 2500) on 04-14-2005, 01:17 PM:

Dear experts,

Can you please let me know what is the differents between the normal Led & a Sr Led which we use in the Sr reader.

Can we use brighter Led in the place of Sr Led?

What is the material used in making this Sr Led's?

Why are they so costally?

Is there any comparitive Led we can use..

Please advice.

Thanks
Peter

Posted by Richard Fowler (Member # 893) on 04-14-2005, 01:58 PM:

Happy New Year....The LED-V chip is the same for analog and digital; you are probably running the LED at different current which you see as different brightness. The more chips you buy the less they cost. [Smile]

Posted by Martin Daian (Member # 1779) on 04-14-2005, 02:10 PM:

Hello Peter, the led's are a design of Dolby, are very special led , are 24 leds array in the same encapsulated epoxy led are 10 times more brighter that a standard led, like 100.000 milicandelas vs 10.000 of the standard led, i have some little quantity for sale if you need.

Posted by Mark Gulbrandsen (Member # 72) on 04-14-2005, 07:07 PM:

If you are having LED life span problems be sure to switch the led off when the projector is idle. OSme use the automation to do this and other just place the power supply across the projector motor circuit. How its done depends on your sound system circumstances. Doing so may give you close to double your present LED life span.

Martin is correct that there are 24 LED segmsnts in it. To be exact there are two rows of 12 led segments. The ground is common to both but each row has its own positive connection. Hence the three pins on it. Good heatsinking is also required for long life span... as you can imagine these little dudes generate alot of heat for theor size.

I replaced all the LED's today in a 6 screen multiplex as all of them had at least several segments that were out. This will cause low analog level and improper decoding by the matrix. This plex was 7 years old and the LED's were on constantly... till today....they are now switched.

Mark

Posted by Michael Schaffer (Member # 1204) on 04-14-2005, 09:05 PM:

Did you tie them to the motor?

Posted by Sam D. Chavez (Member # 1841) on 04-14-2005, 09:30 PM:

The LED can be operated by a relay whose coil is tied across the projector motor.

If the LED is to be turned on and off while the soundtrack is "active" it will cause a thump.

You need to slow the inrush current to the LED on the BACP reader with perhaps a 5000 uF cap in series with a 10 Ohm resistor, both across the LED.

Posted by Mark Gulbrandsen (Member # 72) on 04-14-2005, 09:40 PM:

I think what Sam is referring to is switching the LED's on and off in the DC line, with his readers the resistor and cap would be needed on an always open audio system to eliminate the thump from the LED suddenly biasing the cell. The Kelmar, C.E., or BACP power supply can also be tied right across the motor switched circuit. This is ok and will still meet most code requirements because all these are protected supplies. Its usually very easy to do this in consoles and fairly easy in existing booths with all seperates.
In the Christie projector this is as easy as moving just one wire over.

Mark

Posted by Tom Wienholt (Member # 1510) on 04-14-2005, 09:43 PM:

Will the cap and resistor cause any loss of power to the led?

Posted by Sam D. Chavez (Member # 1841) on 04-14-2005, 11:21 PM:

No current will flow thru the Cap once it is charged up which takes something less than a second.

Of course you could have a very leaky cap I suppose.

Posted by Peter John Anthony. C (Member # 2500) on 04-15-2005, 12:08 AM:

Hi!
My actual problem was, we are using exciter lamps where sometimes we have sound problems. We came to know the same print that we are using is fine with the theatre using Sr Led’s.

I just want to know if we are going for Sr sound reader, what all alteration is required.
How much will be the total cost? Can I use only the Sr Led to the existing exciter preamp & power supply? Can any one give me the details and specifications how this sr Led made. If I give the details to the local Led manufacturer will they help me out…..

Thanks for all your help

Posted by Sam D. Chavez (Member # 1841) on 04-15-2005, 01:47 AM:

I am lost here. What exactly is a Sr LED?

Also, what is an LED V chip?

Posted by Michael Schaffer (Member # 1204) on 04-15-2005, 02:57 AM:

When installing new red LED readers, I have always used the BACP reader. No, really, I have, I am not just saying this because Sam is online here too. Whenever I have had time to do it, I simply wired the convenience output the reader is plugged in with the motor so that the output becomes hot whenever the motor runs. I know the BACP power supply is supposed to be able to be on all the time because of the relatively low LED current. Still, I just think it is very neat for the PS to come on only when the motor is running...Unfortunately, I have not always had the time to do it this way.

Posted by Peter John Anthony. C (Member # 2500) on 04-15-2005, 03:55 AM:

Sam Sr LED is the same one which reads spectral recording sound track.

Both Red LED & Sr LED are the same.

Sorry for confusing you all.

In simple in some of my projector i have exciter lamps used to read sound tracks.

I am facing problems with exciter lamps, so i want to upgrade with Red LED's reader.

What all alteration is required to install the same.

My projector are Photophone and westrex projector.

Please advice me in details.

Thanks,
Peter

Posted by Richard Fowler (Member # 893) on 04-15-2005, 10:05 AM:

Sorry Sam. It is a carry over from the early days from my former stock program to to note the Dolby or USL RLD led chip as LED-V versus IR units.....just a Habit [Smile]

Now we must find the source of the Indian Sr chip [Big Grin]

Photophone soundheads are identical to the RCA soundhead used in the USA. Westrex is similar to Century except the LED mounting foot is different and on some sound lens castings you may have to cut some of the lens tube mount to allow the analog reader to get to the recommended distance from the LED source. The sound drum on most Westrex will need to be turned down on the interior face of the drum to allow clearance for the LED mount. These readers, made by Kelmar, are available in India.

Posted by Mark Gulbrandsen (Member # 72) on 04-17-2005, 10:10 AM:

quote: Michael Schaffer
When installing new red LED readers, I have always used the BACP reader. No, really, I have, I am not just saying this because Sam is online here too. Whenever I have had time to do it, I simply wired the convenience output the reader is plugged in with the motor so that the output becomes hot whenever the motor runs.

This is usually how I do a conversion in the field of an existing projctor. This can also be done for AC powered penthouses. Nothing wrong at all with doing it this way. I have seen some but not much fading in BACP readers that stay on all the time. Its really neglagable compared to everyone elses reader though. Note that with many AC outlets there is a link that can be broken off to allow you to make half the receptacle switched and the other half hot. Just be sure that the AC feeding both those halves are from the same phase or 220V will be present at that outlet [Eek!]

!!! ALso label them so the booth mongers know which is which.

Mark