Let's Make Robots!

Motion Detector

As my ignorance is almost complete, I'm looking for some advice on a suitable sensor to use with a PicAxe for a motion detector. I want to be able to detect a moving person at a distance of up to 2 to 3 meters, over a wide angle. Any ideas welcome - especially zany/arty ones.

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maybe this is a dumb question, but what about a PIR sensor? Do you need to simply detect that something is moving, or track the movement?
You want the program to watch pin3 (which is normally high) to see if it goes low. When the motion sensor detects motion, it will always pull this pin low, so now, you just need to decide what you want to do when this happens. If you are doing walk test, then you will want to tell pin4 to go high and that will light the LED. Now tell it how long to light the LED, and then make that pin low again to turn it off. Now you can force the program to ignore the pin 3 for a certain amount of time and then let it light the LED again. If you were in camera mode, then rather than light the LED, you would make the pin 1 go high for a short time, then set it back to low, this will turn the camera security on, now wait for a second or so (whatever shutter time is needed for your camera) and then make pin0 go high and it will take a picture. Now make pin1 pin go high for a short time, then set it back to low again and the cam will turn off. Now you can force the program to wait for a certain delay again before you let the input from the motion sensor on pin3 have an affect on the program.
or maybe a spider's web spun from fishing line across the furniture
Spiders web: good try but too obvious in daylight.
...Then just pile up a bunch of beer cans for the person to trip over.
Too dificult to reset, and people would just nick 'em ... or tidy them up.
tidying up, tisk!

PIR - http://letsmakerobots.com/node/858 Sorry, not very arty or zany...

For that, how about a moat? Aim an IR sensor at the water, when it ripples someone's too close.

Even better, random flame spurts! Use the "microphone as sensor" thing to pick up the screams.

Both good ideas. I'm aiming for surprise, but perhaps not shock and awe.