Subject: Re: Best way to power array of LEDs?
Date: Sat, 2 Nov 2002 07:51:20 -0800
Organization: Posted via Supernews, http://www.supernews.com
References: <0001HW.B9C26E7400A7161B165FEAC0@news.covad.net> <7tGLdeAS6fn9EwBv@jmwa.demon.co.uk>
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I know I will get shot down here...... but here is a very inexpensive,
SIMPLE and RELIABLE scheme:
Depending on the specifications of the LEDs and how hard you want to drive
them, you can adjust the value of the series dropping resistor. For
example.....In series with each LED, a 680 ohm half watt resistor will limit
the current to each LED to roughly 19 ma.... actually the total current
swing of about 17 ma to 21 ma (a swing of only + or - 10% total) over
the nominal automotive voltage operating range, driving, idling, and the
motor not running. At a total of 36 LEDs, that is a TOTAL current draw of
only 0.75 Amps..... LESS than a side marker or dome lamp..... so WHO CARES
about "wasted power" in the dropping resistors.
So, how complicated is this?....... 36 LEDs and 36 resistors..... not much
to go wrong here.
At that rate, you could hook up 100 LEDs and pull about 2 Amps..... roughly
the same amount as a brake or tail-light...... and the heat and wasted power
from the resistors will still be negligible..... and would not affect your
gas mileage..... or I suppose a single drop of gasoline in several
tank-fulls should take care of the extra power used.
Electronics Supply & Repair
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"R. Lewis" wrote in message
> Amid all the jollity has anyone come up with an economical yet reliable
> of making a 36 led array with anywhere near a standard (constant)