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Abstract

An inductive coupled object identification system (FIGS. 2a and 2b) uses inductive coupling to detect and identify objects. Each object includes an object resonance circuit (LT/CT) with a unique object resonance frequency. Base electronics (50) includes an inductive-coupling base coil (L1) coupled to an oscillator circuit (60). To detect an object, the oscillator circuit continually sends START pulses to the base coil. When an object is proximate to the base coil, a START pulse is inductively coupled to the object resonance circuit, causing it to resonate at the object resonance frequency. This resonance condition is detected by the oscillator circuit, which outputs an oscillation signal FREQ at the object resonance frequency. Frequency counting logic (70) is used to determine the object resonance frequency, allowing a microcomputer (80) to identify the object. Two embodiments of the object identification system are described: a dynamic embodiment (FIGS. 1a and 1b) in which ball-shaped objects (10) are dropped into a bowl (13) through a single base coil (L1) in the rim of the bowl, and a static embodiment (FIGS. 1c and 1d) in which ring-shaped objects (20) are placed over a post (23) incorporating multiple base coils (L1-L5). For the static embodiment, the multiple base coils are multiplexed by a base coil selector circuit (FIG. 2b, 100).

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