On Tue, Feb 21, 2012 at 9:09 AM, David Duffy (AVD) wrote: > I might revisit the PIR modules. =A0Finding something sturdy enough as an > off the shelf product is the ideal scenario. =A0We *could* build sensors, > but I'd rather not just yet as it's just an idea with no commitment to > bulk quantity yet. =A0If I could buy a ready to go sensor with a cable > tail for under $50 in small quantity that would suffice. =A0If the idea > gets up, then we can look at custom made sensors to get the price down. Maybe you can try to look at some photoelectric sensors -- look for "Diffuse Mode" sensors. Sensing range of 1000mm is not a problem. The mutual interference part can be a problem but your requirement may not require such a feature as the distance between the sensors are sufficiently apart. For example, you can search here, not so sure about the "US$50 in small quantity part" as I no longer follow the product closely. http://www.pepperl-fuchs.us/usa/en/classid_47.htm Disclaim: I used to work for Pepperl+Fuchs until 2006. Other vendors include Banner Engineering, SICK, Omron, SUNX, etc. --=20 Xiaofan --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .