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> <3D9D32DE.email@example.com> <firstname.lastname@example.org>
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Date: Sun, 06 Oct 2002 04:50:19 GMT
NNTP-Posting-Date: Sun, 06 Oct 2002 00:50:19 EDT
On Fri, 04 Oct 2002 08:16:31 GMT, email@example.com
(budgie) Gave us:
>On Fri, 04 Oct 2002 08:19:10 +0200, Tilmann Reh
>>> 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 operatin=
>>> current for 9 LEDs
>>> 3) Install voltage regulator to output voltage (ie, 1.3 volts?) to oper=
>>> all LEDs in parallel.
>>> What is the best method to power these from an intermittent (whenever I=
>>> the brake pedal) power source?
>>Better use many LEDs in series to avoid unnecessary power loss.
>>With 12V supply, you can use about 5 LEDs in series and a smaller
>>resistor for each chain. These chains are then connected in parallel.
>The problem with that approach is that, as you put more in series, the
>volt drop across the resistor reduces but the voltage variation due to
>system volts looms up large. As a result, the brightness varies more
>with system volts than single LED/resistor strings.
>As for power saving, that's like not using your parachute because it
>will cause wear. I'm sure he isn't planning on driving around with
>the anchors on all the time.
Power is power. If the LEDs are all lit to the same brightness
level, regardless of configuration, the same power will be moving.