What kind of sensor do I need...

[rkhpedersen]

to detect human beings? I need a sensor to trigger a web cam. The web cam already have motion detection but the problem is that:

1) A human of 2 meters distance appears much lager than the same person 6 meters away. It is therefore impossible to adjust the sensitivity.

2) it's not very sensitive. If a person is sitting by the table reading a newspaper the sensor does not pick up on arm movements etc.

What I would like is for example to detect the persons IR radiation (heat?). Is that possible so the sensor remains triggered while one or more people are in the room?

Thanks for your help.

René Pedersen
The Big Mind

 

[shokjok]

Have you considered a thermal imaging camera? It will detect temperature changes by highlighting warmer areas in the scanned field. From there, you need a waveform monitor to detect the changes to the video signal, similar to PIP.

 

[vne147]

A PIR (passive infared) sensor might work for your purposes. Something like this:

SparkFun Electronics - PIR Motion Sensor

 

[ericwertz]

other source(s) for PIRs

I noticed that the ones at SparkFun are currently out of stock. You may also try here:



or here:

PIR Sensors

or here:

Development and Prototype boards and tools for PIC AVR and MSP430


PIR sensors/modules sometimes claim to be tuned for IR wavelengths for human body temperatures, but I have no idea how well they work in practice with regards to false positives.

Whether any of them meet your sensitivity requirements won't be known until you try them in the conditions that you care about. For only US$10, this isn't so bad.

By the way, you can always narrow their field of view by putting a cone or a tube in front of them.

Also by the way, many PIR modules are poorly designed in that many have no (or terribly small) mounting holes on the PCB. Something to consider.

-e

 

[ericwertz]

or hacking

Forgot to mention that you could also try products that use PIR sensors, like motion-detecting light switches and the like from your local home-improvement store. If they work for you and are the right price, you could probably just remove the sensor to use in your project.

I have a few of the ones from Parallax (see URL above) and they're very, very easy to use. There are documentation links on their website.

-e