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From: email@example.com (Rob Paisley)
Subject: Re: why does IR circuit oscillate?
Date: 27 Sep 2002 21:43:43 -0700
NNTP-Posting-Date: 28 Sep 2002 04:43:44 GMT
It seems very unusual to be driving the RESET terminal of the timer in
order to control the output as is the case in the schematic.
As it is, the timer is guaranteed to oscillate if the RESET terminal
is held high. (It's a version of the unworkable 50% duty cycle
I have posted two possible reworks of the originally posted circuit.
Without actual knowledge of the GP1U52X it is hard to say if they
will work correctly. The receiver must have a digital output.
The.Central.Scrutinizer.firstname.lastname@example.org wrote in message news:...
> In article , Carl Smith wrote:
> >On 26 Sep 2002 13:43:36 -0600,
> >The.Central.Scrutinizer.email@example.com wrote:
> >>The open circuit output of the IR receiver has a little noise, about a
> >>microsecond pulse ever ms or so, but when I connect it to the transistor
> >>buffer, it oscillates nonstop. The power to the IR receiver is clean, I don't
> >>see any noise on it at all. 'scope was connected with the IR receiver's ground
> >>as it's reference.
> >Maybe 10 years ago, or more, I built a wired IR repeater with a
> >IR sensor from Radio Shack that turned the 40KHz IR signal to the
> >straight logic output. The logic output triggered a 555 timer
> >driving an IR LED. Basically the same concept. It worked
> >great, but I don't have the schematic anymore or remember the
> >details of exactly how I did it.
> >The GP1U52X part number sounds very familiar, it may be the same
> >one I used. I do remember that the receiver I used liked to
> >output lots of random logic "noise" until I grounded the case of
> >the sensor to its own ground pin. That cleaned it right up.
> I'm using that 10 year old circuit, more or less. The IR receiver had a
> grounded mu-shield. part # is now 256-137b although I hear the second
> generation part is getting discontinued.
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