Smallest possible motion sensor

Hey, are there any micro/mini PIR sensor out there? The smallest I can find are about the size of a quarter with the big white lense over it. I'm trying to find something smaller and more discrete to embed in a wall in my house. It doesn't need to be PIR, but I just need a little bit of advice to what is out there.

I have one of these: http://www.ebay.com/itm/131225924799 They work. 10mm diameter.

Is this a quarter to you ? http://en.wikipedia.org/wiki/Quarter_%28United_States_coin%29 That is 24.26 mm diameter.

A simple camera would do the trick. Most only need a hole about a tenth of an inch diameter to work. Then a bit of image processing could be used to detect movement.

In fact it's exactly how the sensor in an optical mouse works and with a bit of hacking, all of this functionality is built into it. You'd need to change the lens but it would work.

Thanks. Yea, 20+ ish mm is about right... or a US quarter.

10 mm is a good improvement. Is that as small as they go?

I just need to sense motion in 1 meter by .33 meter area by about a meter in depth.. essentially a narrow hallway or stairway.

KenF: A simple camera would do the trick. Most only need a hole about a tenth of an inch diameter to work. Then a bit of image processing could be used to detect movement.

In fact it's exactly how the sensor in an optical mouse works and with a bit of hacking, all of this functionality is built into it. You'd need to change the lens but it would work.

Do you have any examples of a project that does this for reference? I will have to have multiple sensors, so cost and complexity is a consideration.

Peter_n:
Is this a quarter to you ? http://en.wikipedia.org/wiki/Quarter_(United_States_coin)
That is 24.26 mm diameter.

These (attached) are all quarters to me :stuck_out_tongue:

JimboZA:

Peter_n: Is this a quarter to you ? http://en.wikipedia.org/wiki/Quarter_%28United_States_coin%29 That is 24.26 mm diameter.

These (attached) are all quarters to me :P

/ queue sad trombone sound

:)

You mean the world isn't measured in U.S. quarters?

ekothree:
You mean the world isn’t measured in U.S. quarters?

Well on 9gag it’s bananas.

Here we go, found this.

US quarter, banana for scale. Or is that banana, US quarter for scale.

And a diamond…

quarter and banana.jpg

Ah so that's how big a quarter is! About 2.5 times the diameter of a diamond. BTW that banana is quite small isn't it?