Subject: Re: Best way to power array of LEDs?
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NNTP-Posting-Date: Sat, 05 Oct 2002 00:45:41 GMT
Organization: AT&T Broadband
Date: Sat, 05 Oct 2002 00:45:41 GMT
LEDs are current devices and you need to know the recommended operating
current and the forward voltage drop of them. You can get that info. from
the manufactuer's literature. To find a current limiting resistor, use this
Supply voltage minus forward voltage divided by the recommended operating
So in your case, if the forward voltage drop is 1 volt and the recommended
operating current is 20mA:
------ = 600 so a standard value resistor of 590 Ohms will work.
You can put as many LEDs in series as the voltage will allow ( with a1 volt
drop you could put 12 in a row, so your 9 in a line/row will work great).
So you need three 590 Ohm resistors - one for each row.
Hope this helps.
"DaveC" wrote in message
> Have assembled an array of LEDs for use as a 3rd brake light in my car,
> configured as 4 rows of 9 jumbo LEDs, as of yet unwired. Of course the
> supply will be 12 volts nominal (13.8 volts, maximum).
> My options, as I see them, are:
> 1) Wire individual resistors to each LED based on its operating current
> 2) Wire each row in parallel and connect one resistor based on operating
> current for 9 LEDs
> 3) Install voltage regulator to output voltage (ie, 1.3 volts?) to operate
> all LEDs in parallel.
> What is the best method to power these from an intermittent (whenever I
> the brake pedal) power source?
> Other options for powering this array?
> Note that my return address is corrupted in an attempt to reduce spam. If
> choose to e-mail me, please correct my address as described below.
> Dave Carpenter
> Sound Logic
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