IR proximity sensors and transmitters

Hey guys,

I have a quick question about a setup involving proximity sensors. I'm look for a system whereby several different units can communicate to eachother within a proximity.

If you can imagine a base unit and a zone around this base unit; if a foreign unit should come into this zone an LED on the foreign unit will light up to indicate the boundary has been crossed.

Typical IR proximity sensors detect the distance between an object, I need a sensor to detect if a transmitter is within the defined area.

Please let me know if this can be done and what I will need to buy. Thanks very much in advance, Andy

I doubt this can be done. Every so often we have people asking about two units being to detect how far apart the are and while it sounds easy it is remarkably hard. What sort of range are you looking at?

Thanks for the reply, I see, it would be pretty close, within 30cm. How about turning the floor the objects are to be placed on into a patchwork of sensors, then perhaps a direct connection could be made and communicated based on where the units were placed... Cheers, Andy

You could do it by placing long coils across the floor fed with a 150KHz (or so) signal. This would act as the line.

Then the roving units could pick this up with a coil and detect when it has crossed the line.