At 07:32 AM 11/12/98 -0800, you wrote:
>   AndrŽ, the reason to modulate the IR beam is to prevent the effect of
>saturation. You can normally detect the modulation even under direct sun
>light. While you can do some fancy analog techniques to overcome the
>problem, a simple missing pulse detector will do the job. Given a saturated
>receiver, you can still amplify the signal and detect the missing pulse. I
>use to design IR limit switches for use in very harsh environments back in
>the 70's. We also added a simple light shield (ie: tube), a low-cost IR
>filter, and lenses. We used a 555 timer for the transmitter and a 741
>opamp used as a preamp, followed by a 555 timer to detect missing pulses.
>We tested the system out to several hundred feet with direct sunlight
>focused into the receiver.

As a test, I once used an IR detector circuit (Sanyo I believe) in it's
barest form - detector, 10uF cap, power, and scope probe.

I illuminated the front of the detector with a laser pointer (CW output).
Lots of light!

Next, I blinked my remote control at it.

The remote control signal passeed correctly.

Andy


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Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
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