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tdawson-townsend(at)auror
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 Posted: Sun Jan 27, 2008 1:26 pm Post subject: LEDs at 24volts? |
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I have my reasons, so let's not get into that, but we're building a 24/28 volt airplane.
Question: Can I take an LED with built-in resistor for 12 volt operation (as bought at Radio Shack) and run it at 24 volts? On the bench it seems to operate fine. Even if it reduces LED life somewhat, with the insane life that LEDs have anyway, and an application as warning light that is intermittant at best, maybe it will do fine.
Thoughts?
TDT
RV-10
40025
[quote][b]
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rampil
Joined: 04 May 2007
Posts: 870
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| Posted: Sun Jan 27, 2008 2:52 pm Post subject: Re: LEDs at 24volts? |
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LED Resistor exist to limit the current flow through the LED.
You did not mention want kind of 24v supply you used to test your
12v LED with, I wonder if it had high internal resistance.
Your safest bet is to add a serial resistor, otherwise the lifetime of the
LED may be VERY short
Ira
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Ira N224XS |
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hooverra(at)verizon.net
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| Posted: Sun Jan 27, 2008 6:22 pm Post subject: LEDs at 24volts? |
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If you know or measure the current of the LED at 12 V you can divide 12
by the current and obtain the correct series resistor to maintain the
same current at 24. Assuming about 20ma for a run of the mill led you
would get 600 ohms. 12V across 600 ohms will dissipate .24W so a 1/2
watt resistor would be in order. You will probably find that if the LED
doesn't fail at 24V it's series resistor may!! You will find either 560
or 620 ohm resistors are common values and either would work.
--
Ralph C. Hoover
RV7A
hooverra at verizon dot net
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