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From: zabetia@tiger.UUCP
Newsgroups: sci.electronics
Subject: Re: Infra-Red Receiver?
Message-ID: <180@tiger.Princeton.EDU>
Date: Fri, 3-Apr-87 19:42:33 EST
Article-I.D.: tiger.180
Posted: Fri Apr  3 19:42:33 1987
Date-Received: Sun, 5-Apr-87 10:00:55 EST
References: <1922@ihlpl.ATT.COM> <100500005@datacube>
Reply-To: zabetia@tiger.UUCP (Mahboud Zabetian)
Organization: Princeton U., EE
Lines: 31

In article <100500005@datacube> dje@datacube.UUCP writes:
>
>I generally mistrust  LED markings;  a disease  I picked  up from too
>many Poly-Packs (remember them?)  purchases.   To  check polarity and
>operation at the same time, I use a 330 Ohm resistor in series hooked
>to a 5V supply (20 Ma).  Proper polarity is indicated by the LED on.
>
>				Dave Erickson



Not if it's an Infrared LED.  Unless your eyes were made differently.

Try this:  +5v ------\/\/\/\------>|--------- 0v
		  220ohms    Normal LED

The above circuit is set up.  The LED lights up.  Now take an LED that you are
unsure of and put it in parallel with the first one.  If the first on goes out
or is dimmed, then chances are that the IR LED is emitting.  Otherwise turn the
test LED and try again.


Mahboud Zabetian		allegra! --\	zabetia@tiger.princeton.edu
232 Pyne Hall			mhuxi! -----\		(609) 452-2285
Princeton University		seismo! -----\		(609) 734-0246
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-- 
Mahboud Zabetian		allegra! --\	zabetia@tiger.princeton.edu
232 Pyne Hall			mhuxi! -----\		(609) 452-2285
Princeton University		seismo! -----\		(609) 734-0246
Princeton, NJ 08544		attunix! ------ princeton!zabetia