Subject: Re: current source for array of infrared leds
Date: Wed, 04 Dec 2002 21:39:03 -0800
Organization: MindSpring Enterprises
References: <firstname.lastname@example.org> <4PMG9.email@example.com> <firstname.lastname@example.org>
X-Server-Date: 5 Dec 2002 05:56:37 GMT
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On Wed, 4 Dec 2002 22:30:54 -0000, "R. Lewis"
>"ånønÿmøu§" wrote in message
>> On Mon, 2 Dec 2002 22:13:50 -0000, "R. Lewis"
>> >"ånønÿmøu§" wrote in message
>> >> Maybe you can help me out by answering this question about an LED.
>> >> Will an LEDs' - Vf (forward voltage drop) continue to drop when its
>> >> allowed too much current to flow through it? If so, just how small a
>> >> voltage could you expect it to drop to?
>> >> Would you expect to see: 10%, 20% or more?
>> >Generally an leds resistance (dV/dI) reduces with increasing current,
>> >forward voltage (Vf) reduces as a function of junction temperature.
>> >Theta junction to ambient, for 5mm leds, can be large. If on any length
>> >lead (stand off) it can be huge.
>> They sound like they are too unstable for parallel operation. I have
>> never made a flashlight (or a torch) out of them before. Just displays
>> were each led had its own separate resistor that set the current
>> through it. I haven't put a led into a project going on 2 years now,
>> but you never know when you will.
>Not too many people make torches with infra red leds - even fewer make
I think I can see your point....
>Is it cold on your planet in winter?
Actually, not that bad this Winter.
(But, hardly no rain...)