🚀 go-pugleaf

On Sun, 06 Oct 2002 15:05:04 GMT, JoeBloe
<JoeBloe@thebarattheendoftheuniverse.org> wrote:

>On Sun, 06 Oct 2002 05:36:49 GMT, budgie@nowhere.cantech.net.au
>(budgie) Gave us:
>
>>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
>
>  The power in the LEDs is the same.  The amount "wasted" as everybody
>worries so much about is trivial, at best.


Trivial, absolutely.  But that's different from what you claimed "the
same power will be moving".

Do try to keep up.


>>(b)	I was responding to the P/P's comment about wasting power, on
>>which discussion is just wasting time and bandwidth.
>
>  With the Gazillion bits and bytes flying around the internet
>backbone, I hardly think that 5kBytes of text has put a dent in the
>grand scheme of things.