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From: dya@unc-c.UUCP
Newsgroups: net.analog,net.video,net.audio
Subject: Re: Do-it-yourself IR control?
Message-ID: <1424@unc-c.UUCP>
Date: Thu, 7-Jun-84 08:20:53 EDT
Article-I.D.: unc-c.1424
Posted: Thu Jun  7 08:20:53 1984
Date-Received: Sun, 10-Jun-84 01:45:28 EDT
Lines: 25

References: wateng.1071


    For the IR preamplifier, dig out a copy of Plessey's Radio and Communications
IC book.  Then buy your chips from Motorola -:).  Seriously, you should be able
to use the MC34074A operational amplifier for this.  If you can finagle a
General Insturments hand unit for their Jerrold 400 cable box (this should not
be too hard) then whatever comes out of the preamp is (Probably) ASCII, 50
baud. (No flames about ripping open my cable box, I own it.) They use something
stamped "Motorola" which has the right number of pins for a 68**0*()*/* (for
you Intel folks, that's one of a zillion 6805 variations) but of course the
GI part number.  Pop in the ACIA (etc) of your choice and you are in business.
It looks like a 6805S2 from where the data goes (from the IR preamp).

    As for getting it to ignore room lights, etc. just use a piece of glass
which has been treated to pass IR but sharply attenuate the rest. These are
common.  GI uses red plastic...Kevin's right, though, about getting the
vacuum cleaner's arcing commutator near this, though.  I think that's why
the picked the low baud rate for the transmitter.

    I once had delusions about doing this for a satellite receiver, but found
that too much tweaking is required with those cheap home units to make it worth
while.

dya