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From: csmith@plains.NoDak.edu (Carl Smith)
Newsgroups: sci.electronics
Subject: Re: IR Reception - Modulation and Quality
Message-ID: <10162@plains.NoDak.edu>
Date: 4 May 91 04:16:23 GMT
References: <2766.27E40773@ofa123.fidonet.org> <159639@felix.UUCP> <237@tdatirv.UUCP>
Organization: North Dakota State University, Fargo, ND
Lines: 51

In article <237@tdatirv.UUCP> pa1@tdatirv.UUCP (Pat Alvarado) writes:
>In article <159639@felix.UUCP> dennisg@felix.UUCP (Dennis Griesser) writes:

>>Like half the people on the net, I have been experimenting with the IR
>>detector module made by Sharp, sold through Radio Shack.  There are occasional
>>bursts of optical noise that fool the receiver module into believing that it
>>has seen an IR signal.  I can deal with this.  The incidence is low.
>>Any ideas, gang?

>Could the detector also be picking up levels of IR from ambient light?

Yes.  I am the one who posted about a week ago about the remote control
extender that I built using the Sharp GP1U52X receiver that Radio Shack
sells.  I included a "transmit" LED that flashes when the receiver 
thinks it is picking up and retransmitting a signal.   With two 60 watt
light bulbs on in the room, about 10 feet from the receiver, the
receiver will output short pulses of noise once every 2 or 3 seconds.
This doesn't cause any problem, since the VCR in the other room doesn't
react to the retransmitted pulses of noise.   If you are interfacing it
with a computer, these noise pulses could be a problem...

It IS the lights, cause when I turn them off, the false detections quit.
They quit completely when the room is near pitch black.  Any light at all
seems to cause an occasional glitch.

>Most IR detector units cover the IR detector with a filter that is
>supposed to filter IR levels from ambient light, so the quality of the
>detector may be affected by the amount of IR from ambient light that is
>allowed to penetrate the filter. This could very well be the case where
>the detector is placed where a lot of sunlight is present.

I popped the dark plastic piece out of one of my remote controls and
placed it over the front of the GP1U52X reciever, and the "glitches"
dissapeared completely.  I noticed no decrease in reception distance.
But I have not been able to find a source of this IR filtering plastic.
But I haven't looked to hard... :)

>
>Thanks,
> 
>-- 
>  |||   Pat Alvarado                | 
>   v    Teradata Corporation        | tdat!pa1@suntzu.sun.com
> /\ /\  100 N. Sepulveda Blvd.      | uunet!edsews!hacgate!tdat!pa1
>/// \\\ El Segundo, Calif. 90245    | pa1@tdat.teradata.com


Carl D. Smith Jr.
csmith@plains.NoDak.edu
Electrical and Electronics Engineering
North Dakota State University, Fargo, ND