Prop 1 and PIR

[FAIR1]

   I have read some where in the forums you can limit a PIR's range with a cardboard tube or cylinder. How large a diameter and what length tube dose one need. Do diffrent lengths of tubing not only change the angles at which the PIR can react, but how far from an object it must be to react.

[gadget-evilusions]

Thru my experimentation I found using a tube will restrict the viewing angle of the sensor but not the range so much. I use a 1" length tube the same size as the outside of the lens and get good results. Here is the mounting bracket I use, http://evilusions.com/shop/product_info.php?cPath=55&products_id=1126 . I am posting the link for picture references, not sales references.

[BigRez]

I've mounted my PIRs (when external to the prop) in a device made of the following:

(1) 1 1/2" PVC Cap
(1) 1/2" x 1 1/2" PVC reducer

Drill a small hole in the back of the cap and attach a small 2" 90 degree angle bracket with two small screws.
Paint both pieces flat black (or a color to match your location.)
Mount the PIR inside the reducer with the PIR pointing out the 1/2" side. A small amount of hot glue holds it in place and seals it.
Thread your cable through the small hole in the cap and connect to the PIR.
Connect both PVC pieces together but do not glue. Use Vaseline along outside edge of reduce to help keep moisture out.

This does very well for creating a "beam".  Haven't tried obstructing the opening with anything to see if it reduces the range.

[JonnyMac]

Cutting down the field-of-view probably does affect the sensitivity somewhat, though I suspect when you get a "real" target in your new field all is well.  Last year I put a PIR ins a 4" tube (just big enough to accommodate the PIR) and was able to detect a person 10 feet away -- right were I would have placed a mat switch had I wanted to use one.

Keep in mind that these kinds of "hacks" require experimentation -- there are no formulas that we can use to give a definitive answer.  Experiment.  Experiment.  Experiment -- it's fun.  Then, of course, share your results so that the community can benefit; that's why we have these public forum.