Here's a link to small PIRs that are useful for building into walls, returns or details to make them unobtrusive:

http://uk.farnell.com/panasonic-ew/amn34112j/sensor-motion-10m-110-93-white/dp/1373718

Note that the output is basically TTL and the output is present when there is movement.  To avoid many multiple triggers use a Dwell on a WebBrick and use the driven output in Gateway configuraions.

Andy,

does this mean I simply need to connect the 'output' direct to a DI & independently supply it 5V?

Cheers,

Ian.

 Ian

Yes connect the output directly to a DI.  The 5V output on the WebBrick will power at least 2 of these along with temperature sensors. These a very low energy devices so remember to use the twisted pairs of CAT5(e) correctly; 5V/Ground and Output/Ground.

Configure the DI to use the rising edge, dwell a DO for 2-n seconds and set UDPSend to None (otherwise you'll have a chatty WebBrick).

Each PIR should have its own DI, or use a diode and resistor network to combine.

 Andy

Note: WebBricks only use 50mA at 12V so they are low energy devices.  Low energy low voltage systems need to use twisted pair cables properly to avoid pickup from mains devices. WBs have 20mS de-bounce timers and will filter some degree of hum.  Proper installation will make them bullet-proof from RFI and induced spikes.  I really should write up a separate note.

 Even easier to mount, and cheaper, but not available in black:

Here's a picture of one mounted in a wooden blank plate with a circular hole: http://public.fotki.com/zsalya/webbrick/p6030001.html