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Old 04-20-2007, 09:17 PM   #1
Rze
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Low voltage Light


I need to run a small light for use as a "Light Cue". This is for a small theatre. The light needs to be lit to tell the actor when to enter. From switch to light is between 75' and 100'. The light is the size of a flashlight bulb. Is it best to use DC (9 or 12 V) or Low voltage AC? What is the issue with voltage degradation for DC or low voltage AC over that distance?
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Old 04-20-2007, 10:14 PM   #2
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Low voltage Light


I don't think the voltage drop for such a tiny light is of any concern, but since it is obviously a public building, the fire marshall will probably require any ac to run in conduit.
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Old 04-21-2007, 06:16 AM   #3
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Low voltage Light


If you use a class two or three transformer you will have no concern about the fact that this is an assembly hall.

these units http://www.kele.com/olcat/IM16/TWS-SER.PDF are very bright and draw just a couple mili amps. VD would be little concern.
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Old 04-21-2007, 10:58 AM   #4
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Low voltage Light


Quote:
Originally Posted by troubleseeker View Post
I don't think the voltage drop for such a tiny light is of any concern, but since it is obviously a public building, the fire marshall will probably require any ac to run in conduit.
Actually voltage drop is a much bigger problem with low-voltage lighting over long runs because losing a volt on a 12v system is nearly 10% voltage drop. On boats wiring usually needs to be sized for voltage drop, rather than current rating, even over short runs.

A flashlight bulb can easily draw an amp at 12V (that's only 12W), and on a 100' one-way circuit distance you'd need to use #12 cu to get below 3% voltage drop.

Last edited by NateHanson; 04-21-2007 at 11:07 AM.
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Old 04-21-2007, 11:38 AM   #5
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Low voltage Light


I have used the lights I posted in industrial applications for signaling for machines.

I agree with Nate regarding vd being more of a concern with low volt. I intentionally select this fixture because it is LED and draws less than 1/2 amp at 24 volt, while still being bright enough to be effective. I do not have cma for 18 guage wire, but just guessing 100 foot would not have a huge drop. I would put the power supply near the light, and run a switch loop to the control location. If need be, you could use a pilot relay as a work arround for VD.
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Last edited by jwhite; 04-21-2007 at 11:41 AM.
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