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Subject: Re: current source for array of infrared leds
Date: Wed, 04 Dec 2002 01:22:09 -0800
Organization: MindSpring Enterprises
References: <firstname.lastname@example.org> <4PMG9.email@example.com> <firstname.lastname@example.org>
X-Server-Date: 4 Dec 2002 09:34:59 GMT
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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, its
>forward voltage (Vf) reduces as a function of junction temperature.
>Theta junction to ambient, for 5mm leds, can be large. If on any length of
>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.
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