Low power motion sensor, like Philips SpotOn

Hi all,

Does anyone know what kind of sensor/mechanism could be used by the Philips SpotOn led lights ( http://www.amazon.com/Philips-SpotOn-Motion-Sensing-Portable/dp/B000X92EG6 )? These lights can run for a couple of months on 3 AAA batteries. Of course they are not on all the time, but the motion sensor is.

My goal is to have a small device (Arduino based) with this kind of motion detection that can run a long time on batteries.

Thanks for your ideas!
Jan

edit: the forum didn't like the brackets around my link, corrected

Well, firstly that link is broken.

Now, try Sparkfun or eBay.

Paul__B:
Well, firstly that link is broken.

Now, try Sparkfun or eBay.

Thanks, corrected the link!

I'm aware of these sensors (did some research before posting this Q). But I don't think it's possible to run such a sensor on battery power for a couple of months. They use too much power ...

The pyroelectric sensor itself uses very little power indeed. It is connected to a relatively high impedance (preferably CMOS) quad op-amp. Cheap sensors; presumably cheap but not parsimonious op-amps.

Suggest hacking the thing - buy a couple, deconstruct them (or at least figure out the circuit - I have on various occasions), figure out how to swap in a lower power op-amp, raise resistor values.

First, measure how much current it does use and see just what component is responsible.

How rapidly do you want a response? How much movement? The Sparkfun suggests it settles in two seconds, could perhaps turn it on every 30 seconds, or minute or so?

Alternately, replace the signal processing in the sensor with Arduino - just have a single low-power op-amp buffering the pyroelectric and feed it to an analog input, have the Arduino figure out the rest. Arduino can snooze for a couple of seconds at a time, wake and take a reading.