"The other John Smith" wrote in message
link.net...

"Joe" wrote in message
hlink.net...

Thank you for the info. Today I connected the transmitter data pin to
my
square wave generator with a 1Khz square wave (at 3V peak) and I could
see
it on the receiver output pins, both the linear and digital pins on the
receiver output pretty much the same signal. The only thing I was
confused
about is that, when I first switch the receiver on, the digital output
is
quiet (it goes to 5volts at first and then drops to and stays at zero
volts). Once I transmit the square wave to it and turn the transmitter
off,
the digital output is very noisy (low frequency, I think) and never
settles
back to zero. The linear line comes up to about 2 volts on power up,
shows
a
pretty good square wave when the transmitter is on and then goes back to
the
2 volt level when the transmitter is turned off and stays much quieter.

I can probly filter out the noise on the digital line, or capacitively
couple the linear line to get rid of the dc, but I still need to study
this
more. The range was amazing! I measured about 60 feet (~20meters) and
the
signal was still strong. This was with the receiver in a building and
the
transmitter outside. I can still get more range out of it I am sure, so
I
will be testing that also.


Hi, Joe -

I think the linear output is from the detector in the receiver while the
digital output is following an amplifier with AGC (automatic gain
control).
If so, then you may find that the linear output will decrease in amplitude
with distance but the digital output will stay constant until the range is
so great that the signal drops into the noise. Using the decoder on the
digital output eliminates the noise you see when the transmitter is off.

Sounds like a fun project.

John

Hi John,

Yes, it is fun. Looks like I will be learning about PLLs too. By the decoder
do you mean the holtek? I was not going to use the encoder and decoder,
since this is not a really critical application. I was planning on
generating a square wave with a 555 at the transmitter data pin and then
when the receiver detects it, take a picture. Yes, I think you are right
about the linear pin, because I noticed the magnitude of the received signal
seemed to drop a little with distance, but the digital pin stayed strong the
whole distance when I moved the transmitter from it. The linear pin seems to
be much quieter tho.

I still haven't worked on this yet today, so off I go to work on it some
more and maybe I can get a working circuit soon.

Regards,
Joe
KB1KVI