Unique sensor pairs?

Hello,

I need to build a fake metal detector type device for a museum installation. I am reasonably comfortable with Arduino and have used it for a handful of similar projects.

My task is to hide several sensors in the floor and build a receiver into a fake metal detector build by the props departement. Arduino should then bleep faster and faster as it gets closer to each sensor.

Can anyone suggest the correct type of sensor to use? Obviously ultrasound or infrared can't be used because they will just report the proximity of anything and everything.

What sensor devices can I use that will only report the proximity of this fake metal detector?

Thanks

Well for really small distances like about 7", RFID would work. The nice thing about RFID, is you don't have to power the RFID tag.

I imagine you could use low power 433Mhz radios that each transmit a different id, and then have the Arduino figure out where you are, based on what signals you see.

Thanks I'll do some more research into RFID. 7" may be a bit too small though. I guess I could plant a central tage that are surrounded by several increasing circles of tags, each circle with a different id and reporting a different distance.

Great!

TomSlater:
What sensor devices can I use that will only report the proximity of this fake metal detector?

I suppose you could install a magnet and use some sort of magnet field sensor to detect it. Alternatively - I know it's a wild thought - why not bury something metal under the floor and just use a real metal detector?

PeterH:

TomSlater:
What sensor devices can I use that will only report the proximity of this fake metal detector?

I suppose you could install a magnet and use some sort of magnet field sensor to detect it. Alternatively - I know it's a wild thought - why not bury something metal under the floor and just use a real metal detector?

No need to bury anything. I bet there are plenty of pipes, cables and nails he can 'detect'.

I suppose you could install a magnet and use some sort of magnet field sensor to detect it. Alternatively - I know it's a wild thought - why not bury something metal under the floor and just use a real metal detector?
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This is because the metal detector is actually a mock up of a device that the British Army use to detect IEDs in Afghanistan. It's being built by our props department and will be part of an interactive installation at the Army Museum. We can't have it going off every time it comes it detects metal, it needs to simulate the experience of a bomb disposal squad.