Re: LED temperature dependence

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#2398

From: George R. Gonzalez
Date: Wed, 24 Apr 2002 17:02

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> John Popelish <jpopelish@rica.net> wrote in message
news:<3CC62328.1B2300D2@rica.net>...
> > Adam Seychell wrote:
> > >
> > > I am trying build a photometer that will measure absorption of light
> > > from an high intensity red LED through a substance. Knowing that LEDs
> > > and photodiodes are quite temperature sensitive devices (in terms of
> > > luminescence vs temperature for fixed current) I designed a
> > > compensating photodiode circuit so the LED puts out constant
> > > brightness.

How did you determine you are getting constant brightness?
If you used the same type of photodiode as your leveling detector,
then you have a tautology.

How are you compensating for your detector's temperature sensitivity?

How about keeping the LED at a constant higher temperature with a little
heater resistor?

How about using a 4x brighter LED source-- use one of those new 30Kmcd
LED's,
or just cluster a few LED's.

Regards,

George

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From: "George R. Gonzalez" <grg1@flash.net>
Newsgroups: sci.electronics.design,aus.electronics
Subject: Re: LED temperature dependence
Date: Wed, 24 Apr 2002 12:02:27 -0500
Organization: University of Minnesota, Twin Cities Campus
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