Rf identification system for use in toys

Abstract

A method and apparatus which allows one toy to identify a plurality of objects is provided. The system relies on the inductive coupling of the toy with a tank circuit contained within the object to be identified and therefore does not require physical contact between the toy and the object. The sensing circuit includes a variable frequency RF oscillator and an air wound coil to radiate a magnetic flux which couples to the air surrounding the coil. The resonant frequency of a tank circuit inductively coupled to the sensing circuit serves as the signature for the object. In one approach, the frequency of the RF oscillator is varied over a range of frequencies while the current drawn by the oscillator is monitored. The current draw provides a means of identifying an object since the current will be at a minimum when the oscillator frequency substantially corresponds to the resonant frequency of the inductively coupled tank circuit. In another approach, the object identifying function of the toy is broken up into an oscillation generating step and an oscillation sensing step. During the sensing step, the toy monitors for ringing emitted by the tank circuit of an object, the ringing due to the oscillation of the tank circuit after the oscillation stimulus has been removed.