Hello everyone.
I hope the collective wisdom of this group can aid me.
I am working on a project made up of a series of base stations with an associated mobile tag for each station. The idea is for a base station to be able to respond when its associated tag come in range. Unfortunately, I'm relatively unfamiliar with wireless communications and have been unable to find a suitable solution.
My requirements are:
-------------------------------------------------------------------- The base stations must only detect tags within 1/2 to 1 foot of them (although a slightly smaller range may work also). The base stations must be able to distinguish its associated tag from any others. The tag must draw as little current as possible (I'm planning on powering it with a 3V coin cell battery). Cost is a factor - cheaper is better (obviously).
--------------------------------------------------------------------
RFID would be the ideal option, except that readers are so $%&! expensive.
I've looked into simple Infrared communication, but realize that limiting the communication range would be troublesome and unreliable.
I've toyed with the idea of RF communications, but again, it seems difficult to reliably reduce the communication range, since most manufacturers want to MAXIMIZE range!
I'm intrigued with the possibility of using magnetic fields, but don't really know what direction to go to pursue this.
Basically, I've just about reached the limit of where my knowledge and research capabilities can take me. If someone here could, at least, point me in the right direction, I would greatly appreciate it!