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CardinalNSB(at)aol.com
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 Posted: Wed Oct 08, 2008 4:35 pm Post subject: panel dimmers? |
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Why not go with all LED technology and control the lights with a simple reostat?
What am I missing? Skip
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psamuelian(at)charter.net
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| Posted: Thu Oct 09, 2008 4:50 pm Post subject: panel dimmers? |
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Skip:
LEDs certainly reduce the amount of current necessary compared to incandescent, and a rheostat would perform better in that situation.
However, the rheostat is still changing aircraft power into heat. If you're OK with that, then a rheostat is still the least expensive solution.
There will still be a few calculations that will be necessary so you obtain the correct rheostat and fixed resistance for your particular installation.
What we are aiming for is continuous useful lumen output throughout the entire rotational range of the rheostat without blowing out all the LEDs.
You will have to know in advance how many LEDs you will be lighting and the total current draw.
You can calculate the minimum resistance (highest brightness) from those figures. (Resistance = Aircraft Voltage / Total LED Current). Call this value "Rfixed."
Then you need to find out the maximum resistance that gives the lowest useful lumen output from the LEDs (not off). Call this value "Rmax."
Rheostat resistance = Rmax - Rfixed.
Now we figure wattage:
Rheostat wattage = (Total Current squared x Rheostat resistance) x 2
Rfixed wattage = (Total Current squared x Rfixed resistance) x 2
The "...x 2" is a fudge factor so the resistor is not running at its maximum power capacity.
Place the fixed resistor in series with the rheostat.
Note that this solution does not allow for a bunch more (or less) LEDs as the calculations and resistance would then change substantially. This can happen if you decide to add or delete lighting for some future modification.
Solid state dimmers all use voltage regulation to control lumen output. They regulate the voltage in different ways, but all we're concerned with is if the dimmer/regulator can control the amount of current we need at our design voltage and if its operation is not going to emit RF that will interfere with other equipment. Of course, it would also be nice if it were easy to install, like 1 mounting bushing and 3 wires.
Phil
Why not go with all LED technology and control the lights with a simple
reostat?
What am I missing? Skip
[quote][b]
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