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Help with LED's


Brad Bilger
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I have a situation that I am looking at for next years show. In the middle of my show, I have a large gaping black spot. I have a fountain in the middle. Not a little fountain. 5 sided, about 20' on a side, 2 and a half feet deep. I have found some UL rated, underwater LED lights. (72 super brite LED's, 3" in diameter.) CHEAP. As in $50 apiece. If bought in bulk, the price drops to $27 each. They ain't big, but for that price, I can put a whole bunch of them in the water.

http://www.oceanmistmaker.com/ledwholesales.html

My question for the group is... These LED's are 12 volt AC. I have been in touch with the manufacturer who recommended that they not be run on 12VDC. So, all you electronics wizards.. how you would do it? My first thought was to use a CMB16D until I found out that they were 12 VAC. If you came up against something like this, would you go with SSR's? I'm just looking for some ideas here to plan what I need to get for next year. I know that Dan is coming out with a LOR DIO board soon and would love to look at the specs on it.. I know that plugging a Wall Wart into the outputs of a 1602W and running a bunch of on/off/dim commands is a quick way to put a wall wart into meltdown mode. :P

After looking at some of the stuff that the people on this board have come up with, I know that SOMEONE out there is thinking "Oh, this is so easy"

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I am definitely not certain on this and hope others will chime in as to if this is true or safe. But I am of the understanding that you can use the left side of the board at any voltage with a transformer. I have been told it works like the DC board, you can input 12volts AC on the left side of the board (remove the jumpers first!). The right half of the board has to be 120 volts because it controls the logic, etc. IF this is true, you could hook 12 VAC to the power input on the left 8 channels of the board and still control it.

Don't do this until someone else confirms this or tells me I have it all wrong!

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Here is what I have read that other people are doing for low voltage AC. I have not tested it myself. Power the right hand side of a CTB16PC from 120VAC. This powers the card logic, and gives you channels 9-16 of 120VAC load. Use a step down transformer to feed power to the left hand side of the card with 12VAC. Use channels 1-8 for 12VAC loads. At minimum, I could see where this might need a different resistor between the opto isolator and the triac, and I have not looked at the triac specs to see if it has any issues at this lower voltage. I would also recommend not using the standard NEMA 5-15 cord ends in this application, as there would be too much risk of your 12VAC loads accidentally getting plugged into 120VAC, as well as some risk of 120V loads being plugged into 12VAC, but that generally won't be as entertaining as the other..

- Kevin

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-klb- wrote:

Here is what I have read that other people are doing for low voltage AC. I have not tested it myself. Power the right hand side of a CTB16PC from 120VAC. This powers the card logic, and gives you channels 9-16 of 120VAC load. Use a step down transformer to feed power to the left hand side of the card with 12VAC. Use channels 1-8 for 12VAC loads. At minimum, I could see where this might need a different resistor between the opto isolator and the triac, and I have not looked at the triac specs to see if it has any issues at this lower voltage. I would also recommend not using the standard NEMA 5-15 cord ends in this application, as there would be too much risk of your 12VAC loads accidentally getting plugged into 120VAC, as well as some risk of 120V loads being plugged into 12VAC, but that generally won't be as entertaining as the other..

- Kevin

I'm all for entertainment!:cool:
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Denny wrote:

-klb- wrote:
I would also recommend not using the standard NEMA 5-15 cord ends in this application, as there would be too much risk of your 12VAC loads accidentally getting plugged into 120VAC, as well as some risk of 120V loads being plugged into 12VAC, but that generally won't be as entertaining as the other..

- Kevin

I'm all for entertainment!:cool:

Hey, I'm a firefighter. you would be suprised at what I find "Entertaining"
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One more comment, thinking about possible reasons why they are saying AC only...

They may have half of the LED's configured to run forward biased, and the other half to run reverse biased. If so, and they are resistively current limited, this would probably dim OK. Were they run on DC, only half the LED's would light, and at twice the brightness, which could damage them.

They might be using capacitive current limiting. If so, they won't run on DC at all, but also they should not be dimmed, as it can cause increased brightness and LED failure, or possibly just boring failure of the capacitor... So, if you try dimming them, and they don't dim smoothly, I would strongly recommend using them on/off only.

- Kevin

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Brad Bilger wrote:

I know that plugging a Wall Wart into the outputs of a 1602W and running a bunch of on/off/dim commands is a quick way to put a wall wart into meltdown mode. :D

If you stick to 100% ON and OFF, and stay away from dim, ramp, twinkle, or shimmer, then this should work ok, although you may need a resistive load (like a 3-watt bulb) in parallel with the wall wart.
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