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From: "R. Lewis"
Subject: Re: current source for array of infrared leds
Date: Wed, 4 Dec 2002 22:30:54 -0000
Organization: Nextra UK
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NNTP-Posting-Date: Wed, 4 Dec 2002 22:29:21 +0000 (UTC)
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"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
Is it cold on your planet in winter?
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