Subject: Re: Best way to power array of LEDs?
Summary: What do you think of these ping times eh?
References: <0001HW.B9C26E7400A7161B165FEAC0@news.covad.net> <firstname.lastname@example.org>
X-Newsreader: Forte Agent 1.91/32.564
Date: Sun, 06 Oct 2002 05:08:40 GMT
NNTP-Posting-Date: Sun, 06 Oct 2002 01:08:40 EDT
On Fri, 4 Oct 2002 09:14:21 +0100, Keith Wootten
>In message <email@example.com>, "Wouter van Ooijen
>>>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 power
>>>supply will be 12 volts nominal (13.8 volts, maximum).
>>>What is the best method to power these from an intermittent (whenever I press
>>>the brake pedal) power source?
>>The crucial point is that when you put a resistor and N LEDs in
>>series, the LEDs will take roughly a constant voltage so all voltage
>>variation from your battery will be over the resistor, thus causing
>You can mitigate this to a useful extent by using a small filament bulb
>instead of a resistor. The positive temperature coefficient of the bulb
>will help to keep the current variation reasonable as the supply voltage
>changes. The bulb should be selected to run at more or less normal
>brightness at maximum supply voltage while passing maximum LED current.
Well now. There's a nice, warm, cozy circuit box for ya.