Fmc Led Backlighting Help !

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10-19-2008, 04:31 AM
jonnydaz53

Fmc Led Backlighting Help !

hi all need a some advice regarding backlighting for my opencockpits fmc.

Im using the output card from opencockpits which gives 50 volts per output and 500 ma. And i need to run around 20 x 3mm or 5mm leds for backlighting . Can anyone tell me what leds i should buy (as in votages) and resistors plus how i should wire them serial or parallel and how many outputs to use .

Im a novice with this.

thanks

jonny d
10-19-2008, 04:28 PM
jonnydaz53

any idea,s anyone?
10-19-2008, 04:48 PM
mpl330

Hi,

Maybe this could help?
http://led.linear1.org/led.wiz

Cheers
Mike
10-19-2008, 04:56 PM
salautom

Hello Jonny,

maybe jou can have a look at:
http://www.hebeiltd.com.cn/?p=zz.led...tor.calculator

but why are you using the output card for backlighting?
why not using 12V from a PC powersupply?

I use bright green leds for my cdu backlighting (see my site, pictures)
the leds I use have a voltage drop of 3.8V so I connect 2 leds in series with a resistor of 220 ohm, you can connect several of these combinations parallel to your powersource.

resistor calculation:
powersource 12V - (2 x 3.8V drop) = 4.4V
divide that by the led amp (usualy 20mA), this gives you 220 ohm as a resistor.
10-19-2008, 05:34 PM
jonnydaz53

thanks for the reply the reason i was going to use the output card is because i thought if i connect all the backlighting this way i can control the dimming of the light through the software ie sioc.

what do you think?
10-19-2008, 05:43 PM
Kennair

Quote:

Originally Posted by jonnydaz53

hi all need a some advice regarding backlighting for my opencockpits fmc.

Im using the output card from opencockpits which gives 50 volts per output and 500 ma. And i need to run around 20 x 3mm or 5mm leds for backlighting . Can anyone tell me what leds i should buy (as in votages) and resistors plus how i should wire them serial or parallel and how many outputs to use .

Im a novice with this.

thanks

jonny d

Jonny, I've just bought a pack of 100 super bright 5mm LED's from HERE. Very cheap and plenty of them. And as already mentioned, no need to waste your output card just use a 12v power pack with resistors For a good example of the building process and resistor calculations have a look HERE.

EDIT. I just read your previous reply. Yes the ability to adjust brightness via SIOC is a good one and in fact used by Opencockpits with their backlit EFIS unit. Just be mindful that given the number of LED's you need to backlight a panel, you'll quickly reach the limit of outputs on the card. If you're using it just for the FMC then you're fine.

Ken.