We've talked (on and off) over the last year about interactive displays for Christmas and Halloween. I'm still keen to find reliable ways to detect people and trigger animations, etc. I think we need to sense people in the 500mm to 1500mm range. Proportional (range) sensing would be good too, as you could change / increase the effect as people get closer. Breaking a beam of IR light is easy, but requires alignment and you can't always access both sides of the detection area. I have found a couple of sensors that may be suitable. One is a narrow view PIR sensor that is in quite a small package, but purely on/off sensing. The other is a proportional reflective IR sensor that looks for an IR beam bounced back from an object. Both are on order from O/S and I'll test them once they arrive. I have tried an ultrasonic range sensor (robotics type) that works quite well, but the transducer is quite open to dust and water ingress so wouldn't last long outside. Does anyone have any other ideas? Maybe someone here works with industrial machinery and knows of a low cost solution?