Is it possible to buy or create a very sensitive reed switch?

[vilainoiseau]

I want to create senors that turn some LED's on(or off) when a small magnet comes close (2-6 inches). I want to create these sensors for a laser tag like game only with Nerf Vortex disk guns with a small magnet embedded in the disk. The magnet would probably have to weigh no more than a penny.
Thanks.

 

[galaxy]

I think you may find that a reed switch won't be suitable, would have to be a big magnetic field and they are relatively slow to re-act.. A Hall effect device may be better, but the range is still a problem,

What about RFID tags. They can be passive, and are small and lightweight, way less than a penny (I am in Australia and we don't have penny's, but I think I get the idea).

Some of the RFID systems can have quite large detection ranges. Think security tags in stores and RFID detection of rail cars etc.

 

[vilainoiseau]

Thanks Galaxy, that sounds like it will be a good option. There are some small and cheap RFID tags on ebay. I just need to find some relatively cheap RFID sensors (around $10 USD if possible) that can be used to switch the LED's lights on or off.