People presence detector?

[djpark]

I am looking for some ideas how to detect the presence of people standing or passing in front of a exhibition boot so that a preassigned application can be started.

The "auto flush" system in the public washroom may be one similar example. I am hoping to make one to send the possibility or provablity of the presence to the PC using serial port or USB.

I would appreciate any suggestion on the hardware selection or design.

TIA,

-- dj

[Mark]

The kind in the restrooms are IR. What you are looking for is an occupancy sensor. Basically they usually are either IR or ultrasonic. There exists dual mode sensors that have both but I believe Wattstopper has a patent on that. If your goal is just to do a one up thing for a booth, then just go buy an off the shelf sensor and connect it up to a pic. Most output a 24V signal. A few of the older devices had an open collector output.

[rnielsen]

You could use a simple motion sensor that is common to automatic door openers or security systems. But, then again, you could use a sniffer to detect B.O. (body odor).

Ronald

[MikeValencia]

Probably a motion sensor (usually microwave) wouldn't be a good idea since it would only detect movement. A person merely passing by without any intention to view the exhibit would set off false alarms and you'd start the presentation to an empty audience.

So an ultrasonic or infrared sensor would be the best bet. Since i work in the automatic door industry, i've seen "presence" sensors (like the ones you see above a sliding door threshold) use infrared more often than ultrasonic. Both have its own weakness - e.g. ultrasonic sensors can't detect porous objects, whereas infrared sensors have a harder time detecting darker objects, and especially objects which bear the same color as the background. Note that a "reference" snapshot is taken of the background (usually in the form of an analog voltage). Any difference (with some hysteresis) in later snapshots would indicate a presence.

If it's just for demo purposes, you're better off just buying a kit from Jameco or Digikey or Mouser. I have seen a few of these kits in Jameco catalogs. But i havent seen any in digikey or mouser, but probably because i just overlook them in the B&W catalogs.