Electronics Forum / Basics / February 2006

Hi, Farha.  There are always more than the two horns of the DILEMMA,
even if the third is just to do nothing.

However, I'd suggest you Google "PIR motion detector", and go from
there (and yes, the IR means infrared).  These are usually used with
intrusion detectors in commercial security setups.  The sensors
themselves aren't too expensive, either.  You'll probably have a lower
total project cost with one of these, too.

Good luck
Chris

Hello Farha,

My answers are from my low budget hobbyist perspective.

Is this used in the day or night or both. Indoors or Out.

Narrow field of view?   What distance?

Ultra-sonic motion detection can be a good approach.

I agree with Chris (cfoely1064) that passive infrared methods are
probably easiest setup.

In your design do you want to use laser or active infrared for the
detection of a beam break, which would require opposite sending and
receiving side modules? This could give reasonable distance and
stability using a laser pointer type diode? This could work day or
night with certain alignment difficulties. Pulsing the beam can help
against false triggering used with a missing pulse detector circuit.
(555 type circuit)

The longest range of motion detection I have experimented with is
using Optical (phototransistor), which could detect the shift in
background changes in daylight. Distances of over 100 yards are easily
achievable. This was set up with a pinhole inside of a 12" tube, which
narrows down the field of view at a good distance.

Every method above has distinct advantages and major disadvantages.

I experiment with Theremins, which are the ultimate motion sensors

Good Luck, if you have not already finished your project.

RS Theremin

   * * *
Christopher

Temecula CA.USA
http://www.oldtemecula.com