Inductive sensory apparatus

An inductive sensory system is provided. The system includes at least one object encoded with conductive material and a reader for use in detecting the presence or absence of the conductive material in the coded object. The reader includes a plurality of single coils and detection means for measuring changes in the self inductance of the coils due to the presence or absence of conductive material in the object. The sensory system further includes control means interconnected to the detection means. The control means are adapted to receive a signal from the detection means, translate the signal and generate a control signal for transmission to an external reactive member such as a light, sound or voice generator.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to an electronic sensory apparatus 
and, more particularly, to such apparatus for determining the identity and 
position of a conductive pattern or object in close proximity to the 
sensory surface of the apparatus. The invention has particular application 
in the area of toys, games and publishing, where it may be used to 
identify the presence and location of individual objects or game pieces, 
or of a pointing device, used to select a word or picture in a book. It 
may also be used to "read" data from an individual card placed upon a card 
"reading" surface. Such cards may include playing cards, educational and 
language flash cards, game cards or sports cards and may be used in 
playing a game, in triggering a particular sound or voice, or to initiate 
a certain mechanical action or a visual display. Because of the unique 
design of the present invention, several cards may be "read" 
simultaneously, without the need to "swipe" them through a card reader 
device. 
Most "presence sensor" devices use reed switches and magnets to track the 
motion of magnetic elements. These devices usually have one reed switch 
placed under a plurality of discrete positions on the sensor. When an 
object with a magnet integrated therein is placed in a particular 
position, the reed switch is activated and remains closed until the object 
is removed. In this way the position of the objects placed on the sensor 
may be determined and tracked. 
However, such devices cannot determine the identities of the objects placed 
upon the surface of the sensor. Only when specific, predefined objects are 
placed in predefined positions on the sensory surface--such as chess 
pieces placed in their opening positions on a chess board--can such 
devices determine the identities of the objects placed upon the sensor. 
Furthermore, such devices are often inaccurate if the objects are moved 
quickly, or if two objects occupy the same position on the sensory 
surface. 
The present invention uses the phenomenon of the change in inductance of a 
coil of wire that occurs when a conductive element is brought near the 
coil to detect a conductive pattern imprinted on the surface of an object 
or to determine the location of a conductive object placed above the 
surface of the sensory apparatus. The conductive pattern may be detected 
on the page of a book, on a card or sticker or from any other surface or 
object imprinted with the pattern. The apparatus would be able to "read" 
the codes imprinted upon the object, and trigger or control an action 
based upon that code. Such an implementation of the apparatus is 
particularly useful in the field of electronic learning aids. A flashcard 
or the page of a book may be imprinted with a conductive code, which, when 
read by the sensor, would trigger the playback of a word or sentence that 
corresponds to the flashcard or page. Such a sensor has many uses as a 
game device. For example, the sensor may be used in conjunction with a 
board game in which "secret codes" are invisibly imprinted on playing 
cards. The sensor can also be used with a bowling game to determine how 
many pins have been knocked down. Furthermore, the location of any object 
may be detected by the sensor, as long as a conductive material forms part 
of the object. For example, a doll's hand, a magic wand, a pen or a 
player's token may be detected by the apparatus. The code generated by the 
conductive pattern or object can serves to trigger a variety of specific 
audio, visual or mechanical effects, such as playback of a line of a story 
or the sound of a dog barking when a specific area on the apparatus is 
pointed at with a conductive device. 
2. Description of the Prior Art 
The prior art fails to specifically address either the problem or the 
solution arrived upon by applicant. Inventors have long been trying to 
come up with devices to determine the identity and position of objects, 
particularly game pieces, on a sensory surface. See for example, U.S. Pat. 
No. 4,492,581 which issued to K. Arai et al. on Jan. 8, 1985 for a 
Gameboard Teaching Apparatus. See also, U.S. Pat. No. 4,981,300 which 
issued to E. Winkler on Jan. 1, 1991 for Sensory Games; U.S. Pat. No. 
5,013,047 which issued to G. Schwab on May 7, 1991 for an Apparatus for 
Determining the Identity and Position of Game Objects; U.S. Pat. No. 
5,082,286 which issued to P. Ryan et al. on Jan. 21, 1992 for Sensory 
Games; and U.S. Pat. No. 5,129,654 which issued to B. Bogner on Jul. 14, 
1992 for an Electronic Game Apparatus. 
Furthermore, the electronic phenomenon of inductance in a coil has long 
been established. Electronic devices incorporating inductive technology 
are similarly not uncommon. See, for example, U.S. Pat. No. 4,605,844 
which issued to D. Haggan on Aug. 12, 1986 for a Computerized Transaction 
Card with Inductive Data Transfer; and U.S. Pat. No. 4,818,853 which 
issued to T. Ohta, et al., on Apr. 4, 1989 for a Data Card With Inductive 
Signal Transfer Device. 
As will be appreciated, however, none of these prior patents even address 
the problem faced by applicant let alone offer the solution proposed 
herein. 
SUMMARY OF THE INVENTION 
Against the foregoing background, it is a primary objective of the present 
invention to provide an electronic inductive sensory apparatus for 
determining the identity of a conductive pattern placed in close proximity 
to the sensory surface of the apparatus. 
It is a further object of the present invention to provide such an 
electronic sensory apparatus that senses the position or presence of a 
conductive object in close proximity to the sensory surface of the 
apparatus. 
It is yet another object of the present invention to provide such an 
electronic sensory apparatus that is able to activate a specific audio, 
visual or mechanical effect that is triggered by the specific conductive 
pattern or object. 
To the accomplishments of the foregoing objects and advantages, the present 
invention, in brief summary, comprises an inductive sensory system which 
includes at least one object encoded with conductive material and a reader 
for use in detecting the presence or absence of the conductive material in 
the coded object. The reader includes a plurality of single coils and 
detection means for measuring changes in the self inductance of the coils 
due to the presence or absence of conductive material in the object. The 
sensory system further includes control means interconnected to the 
detection means. The control means are adapted to receive a signal from 
the detection means, translate the signal and generate a control signal 
for transmission to an external reactive member such as a sound or voice 
generator. 
In a preferred embodiment, the reader includes a matrix of coils etched 
onto a thin PC board. A microcontroller multiplexes the individual coils 
or groups of coils by connecting them sequentially to an LC oscillator 
where they act as inductors in the oscillator circuit. Changes in the 
inductance of any coil result in a corresponding change in the amplitude 
and frequency of oscillation of the oscillator circuit. The oscillation 
amplitude of each coil is compared against at least one voltage threshold 
by an amplitude comparator circuit. The amplitude comparator circuit is 
sampled by the microcontroller to detect the inductance of each coil. The 
microcontroller then assigns a value to each coil that is determined by 
the inductance of the coil. By assigning a value to each individual coil 
or coil group, the microcontroller determines the code that uniquely 
identifies the object placed next to the electronic sensory apparatus. The 
apparatus may be used to detect unique multi-bit ID codes printed on 
cards, pages of books or other objects and trigger specific audio or 
visual effects or mechanical actions appropriate for the specific 
multi-bit ID codes. The apparatus may also be used to sense and determine 
the location or presence of any conductive object placed above the surface 
of the apparatus.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to the drawings and, in particular, to FIGS. 1-2 thereof, the 
electronic sensory apparatus of the present invention, referred to 
generally by reference number 1, consists of a matrix of coils 10 embedded 
in the surface of the apparatus. In the preferred embodiment, the coils 10 
are etched onto a PC board (not shown). A multiplexor 12 selects the 
individual coils 10 by connecting them sequentially to an LC oscillator 14 
where they act as inductors in the oscillator circuit. Changes in the 
inductance of any coil 10 results in corresponding changes in the 
amplitude and the frequency of oscillation of the oscillator circuit. The 
oscillation amplitude of each coil 10 is compared against at least one 
voltage threshold by a amplitude comparator 16. The amplitude comparator 
16 is sampled by a microcontroller 18 to detect the inductance of each 
coil 10. The microcontroller 18 then assigns a value to each coil 10 that 
is determined by the inductance of the coil 10. By assigning a value to 
each individual coil 10, the microcontroller 18 determines the code that 
uniquely identifies the object placed next to the electronic sensory 
apparatus 1. 
The number and size of the coils 10 depends upon a number of factors, 
including: (1) the number of bits used in the code patterns to be 
detected; (2) the number of code patterns to be simultaneously detected; 
and (3) the number of discrete locations where the presence of a 
conductive object is to be determined. In the preferred embodiment, the 
coils 10 of the apparatus 1 of the present invention are 3/4 inch in 
diameter, using approximately 10.5 turns per coil 10 with approximately 
0.015 inch line width and spacing. Using these dimensions, up to 4095 
binary codes can be represented on an area the size of a standard playing 
card, or up to 12 discrete locations can be mapped on the same area. If 
more codes or more discrete locations are desired, the diameters of the 
coils 10 may be reduced. However, this reduction requires reducing line 
widths, and results in reduced inductance, making circuit design more 
critical. 
In the preferred embodiment, the coils 10 are etched on a 0.031 inch PC 
board (not shown), with the coils 10 on the underside of the board, 
leaving the top side of the PC board flat. By placing the coils 10 on the 
underside of the PC board, the surface of the apparatus 1 may be made 
flat, allowing objects to be placed directly on the surface. For the 
apparatus 1 to be effective, it is desirable to keep short distances--no 
greater than 1/8 inch--between coils 10 and the conductive patterns or 
objects. 
The coils 10 may be arranged on the surface of the apparatus 1 in any 
pattern. However, in the preferred embodiment, the coils 10 are arranged 
linearly in rows and columns in a checkerboard pattern. In an alternative 
embodiment, the coils 10 are arranged in a series of concentric circles. 
The only requirement as to the arrangement of the coils 10 on the surface 
of the apparatus 1 is that the pattern of coils 10 must match the pattern 
of conductive elements on the object to be "read" by the sensor. 
A particular coil 10 is selected by the coil multiplexor circuit 12 
consisting of at least one 74LS156 (octal) or 74LS05(hex) open collector 
chips. In an alternate embodiment, discrete bipolar transistors may also 
be used for coil 10 selection. Grounding a coil 10 effectively connects 
the coil 10 to the LC oscillator 14 by creating a ground path through the 
coil 10, thus enabling the LC oscillator 14. The frequency and amplitude 
of oscillation in the oscillator circuit will change whenever a conductive 
material is brought within close proximity of a coil 10. The baseline 
frequency of oscillation of the oscillator circuit depends largely upon 
the size and number of turns in the coils 10. In the preferred embodiment, 
the oscillator circuit operates at approximately 2.5 Mhz. The LC 
oscillator 14 operates at a very low oscillation amplitude of only a few 
hundred millivolts in order to minimize the effect of any external RF 
radiation from the circuit. 
The amplitude comparator 16 compares the amplitude of the oscillation of 
each coil 10 against an amplitude threshold, which is predefined as the 
oscillation amplitude of the coil 10 when there is no conductive material 
nearby. In an alternative embodiment, the amplitude threshold may be 
variable, as set by the microcontroller 18, in order to optimize the 
sensitivity of the sensor to compensate for variations in coil 10 
inductance and lead lengths, and to allow for greater distance between the 
coils 10 and the conductive material or code. 
The amplitude converter 22 converts the peak to peak amplitude of the LC 
oscillator 14 output to a DC level which is compared to the amplitude 
threshold. The presence of conductive material next to a given coil 10 
reduces the oscillation amplitude, driving the voltage level at the 
negative input of the amplitude comparator 16 below the threshold set at 
the positive input, resulting in an increased comparator 16 output. If 
conductive material is not present above the coil 10, the comparator's 16 
output will be low. 
In an alternate embodiment, the change in inductance of the coils 10 may be 
effectuated by comparing the oscillation frequency of the coils 10 against 
a threshold frequency or frequencies. 
In the preferred embodiment, the multiplexing and sampling of the coils is 
controlled by the means of a combination microcontroller and voice chip 
18. In alternate embodiments, the same control may be achieved by a 
microcontroller chip with or without a separate voice chip (not shown) or 
by a discrete logic controller or ASIC chip (not shown). The 
microcontroller chip 18 sequences through the various coils 10 by applying 
a coil select address to the coil multiplexor circuit 12, waits a fixed 
time interval (a few milliseconds) for the voltage detection circuitry to 
settle, and reads the coil 10 "state" from the amplitude comparator 16. 
Knowing the state of all the coils 10 reveals the ID code printed on the 
object or the location of a conductive object within the area covered by 
the coils 10. This information can be used to trigger specific events, 
such as the playback of the appropriate words or sounds in the voice 
memory that correspond to the picture pointed to or printed on the object 
covered by the sensor 1, the activation of visual or sound effects or the 
initiation of mechanical actions, such as activation of an electronic lock 
or security system. 
In the preferred embodiment, each coil 10 is assigned a value of zero (0) 
if there is no change in the inductance of the coil 10, and a value of one 
(1) if there is any significant change in the inductance of the coil 10. 
Thus a binary code is generated by sampling the matrix of coils 10. This 
code may then be used to trigger specific audio effects, visual effects or 
mechanical actions by the microcontroller and a voice chip. Alternatively, 
the code may be used to determine the position or positions of at least 
one conductive object placed above the surface of the apparatus 1. 
In an alternate embodiment, several different values may be assigned to 
each coil 10 or groups of coils 10 depending upon the number of turns of 
the coil(s) covered by conductive material which affects the oscillation 
amplitude of the coil 10. A different value may be assigned to each coil 
10 depending upon whether the oscillation amplitude reaches certain 
predefined threshold levels. In such an embodiment, the sensitivity of the 
amplitude converter 22 is very critical. 
In the preferred embodiment, the electronic sensory apparatus 1 of the 
present invention is battery 24 operated. A voltage regulator 26 may be 
used to maintain a constant voltage to the LC oscillator 14 and coil 
multiplexor circuitry 12. The voltage regulator 26 acts to prevent a 
change in the supply voltage from seriously affecting the amplitude of 
oscillation in the oscillator circuits created with the individual coils 
10. In the preferred embodiment, a Zener regulator may be used to maintain 
a constant voltage. In an alternate embodiment, the Zener regulator may be 
replaced by a 78L05 voltage regulator, which provides better regulation at 
greater cost. 
Having thus described the invention with particular reference to the 
preferred forms thereof, it will be obvious that various changes and 
modifications can be made therein without departing from the spirit and 
scope of the present invention as defined by the appended claims.