🚀 go-pugleaf

On Sun, 06 Oct 2002 04:50:19 GMT, JoeBloe
<JoeBloe@thebarattheendoftheuniverse.org> wrote:

>On Fri, 04 Oct 2002 08:16:31 GMT, budgie@nowhere.cantech.net.au
>(budgie) Gave us:
>
>>On Fri, 04 Oct 2002 08:19:10 +0200, Tilmann Reh
>><tilmann.reh@autometer.de> wrote:
>>
>>>DaveC schrieb:
>>>> =
>>>
>>>> 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).
>>>> =
>>>
>>>> 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=
>>>g
>>>> current for 9 LEDs
>>>> 3) Install voltage regulator to output voltage (ie, 1.3 volts?) to oper=
>>>ate
>>>> all LEDs in parallel.
>>>> =
>>>
>>>> What is the best method to power these from an intermittent (whenever I=
>>> press
>>>> 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.

(a)	you're wrong, because that ignores loss in the resistors
(b)	I was responding to the P/P's comment about wasting power, on
which discussion is just wasting time and bandwidth.