BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to, in general, fitness equipment, and more particularly, to an apparatus, system, and method for determining the amount of weight lifted on an exercise weight machine.

2. Background Fitness equipment, such as weight machines having numerous weight plates arranged in a stack, permits a user to exercise and strength condition by performing various exercises using different amounts of weights on variously configured weight machines.

In recent years, these weight machines have been equipped with electronic devices to determine how much weight is lifted by a user during an exercise, either per repetition or the total of several repetitions. For example, the SCHWINN FITNESS ADVISOR (a registered TM), sold by Schwinn Cycling & Fitness, Inc., uses a load cell mounted at the base of the stack of weight plates to determine how much weight is lifted. The load cell is a transducer which provides a signal representative of the amount of weight imposed on the load cell at a given time.

Another approach utilizes an optical emitter/sensor pair positioned in a fixed location to determine the number of plates passing by the emitter/sensor pair to determine the amount of weight lifted. A third approach includes using an encoder attached to a wire connected to the selector pin of the weight machine to determine the amount of weight lifted. As the selector pin is inserted in the receiving aperture of a weight plate, a different signal is generated corresponding to the weight plate selected.

These existing devices are complex, expensive, and can be difficult to install. What is needed is an apparatus, system, and method for determining the amount of weight lifted on an exercise weight machine having a plurality of weight plates arranged in a stack, wherein the means for determining the amount of weight can be easily installed onto existing weight machines or incorporated into the design of a new weight machine.

SUMMARY OF THE INVENTION According to one broad aspect of the invention, disclosed herein is a method, circuit, and system for determining the amount of weight lifted on an exercise weight machine during an exercise by a user, wherein the weight machine has at least a first and second weight plate arranged in a stack. A first module is mounted to said first weight plate, and a second module is mounted to said a second weight plate, and the first and second modules interact with one another and detect if said first weight plate is in close proximity to said second weight plate. The first and second modules are in communications with a microcontroller which determines the amount of weight being lifted from the stack.

In one example, the first module and second modules each have at least a pair of conductors with an electrical element connected therebetween, the conductors first module adapted to contact the conductors of the second module, so that when the first and second weight plates are substantially together in the stack the electrical elements form a parallel circuit. The microcontroller determines the amount of weight lifted during an exercise based on the effective impedance of the parallel circuit.

In another example, the first module has the ability to detect the presence of the adjacent second module and transmits a unique signal to the microcontroller when the first and second weight plates are substantially separated from each other (i. e., when the second weight plate is lifted and separated from the stack) during exercise. Based on the received unique signal, the microcontroller determines the amount of weight lifted during exercise.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates a stack of weight plates of a weight machine with a representation of a set of resistive elements, each associated with a weight plate in a stack, arranged in parallel to form an effective plate impedance or resistance, Rp, in accordance with one embodiment of the present invention.

Fig. 2 illustrates a block diagram of a remote station sensor system for a weight machine in accordance with one embodiment of the present invention, wherein the sensor system has a sensor for determining the amount of weight lifted, and an ultrasonic range sensor to determine the speed and range of motion of the weight lifted.

Fig. 3 illustrates a block diagram of a plurality of remote stations coupled through a wireless network to a central kiosk for updating and

storing detailed records of a person's workout preferences, history, performance, etc.

Fig. 4 illustrates a circuit diagram employing a voltage divider network wherein the effective plate impedance Rp is used, in accordance with one embodiment of the present invention, to determine the amount of weight lifted.

Fig. 5 illustrates a graph of the output voltages generated by the resistive divider of Fig. 4 as the number of plates lifted during exercise changes.

Fig. 6 illustrates an alternative embodiment of the present invention wherein the effective plate impedance Rp is used to vary the time constant of an oscillator circuit to alter the frequency or duty cycle of the oscillator circuit.

Fig. 7 illustrates a graph of the changes in the period of the output signal of the oscillator circuit of Fig. 6 as the number of plates lifted during exercise changes, in accordance with one embodiment of the present invention.

Fig. 8A illustrates a module housing an electrical element (i. e., resistor) therein, which can be attached to adjacent plates to form an electrical circuit therebetween.

Fig. 8B illustrates an alternative embodiment wherein the conductors and electrical elements are positioned within the weight plate.

Figs. 9-10 illustrate perspective views of one embodiment of a module of the present invention, wherein a surface mount electrical element (i. e., resistor) is positioned within a slot of the module.

Fig. 11 illustrates a top view of the module of Fig. 9.

Fig. 12 illustrates a rear view of the module of Fig. 9 in accordance with one embodiment of the present invention.

Fig. 13 illustrates a bottom view of the module of Fig. 9.

Fig. 14 illustrates a section view taken along section lines 14-14 of Fig. 13 of the module in accordance with one embodiment of the present invention.

Fig. 15A illustrates a pair of adjacent modules mounted on separate weight plates, in accordance with one embodiment of the present invention.

Fig. 15B illustrates an alternative embodiment of the module of Figs. 9-15A wherein the contacts are inwardly curved along the top side of the module, and a pair of conductive plates are positioned along the bottom side of the module to couple to the contacts of the adjacent lower module.

Fig. 16 illustrates an alternative embodiment wherein the modules are U-shaped modules attached along the side or end of the weight plates in accordance with one embodiment of the present invention.

Fig. 17 illustrates a pair of non-contacting modules coupled to their respective weight plates in accordance with an alternative embodiment of the present invention.

Fig. 18 illustrates one embodiment of the non-contacting modules of Fig. 17 wherein each module has a set of capacitive plates which forms a pair of air gap capacitors when positioned proximate an adjacent plate.

Fig. 19 illustrates a representative circuit diagram of a set of four modules of Fig. 18 which are placed on four weight plates, and three

pairs of air gap capacitors which are formed between adjacent modules.

Fig. 20 illustrates an exemplary graph of the capacitance varying as a function of the gap between the plates of a capacitor.

Fig. 21 illustrates an exemplary graph of the impedance of a 1-pico-farad capacitor over various excitation frequencies.

Fig. 22A illustrates an alternative embodiment of the non-contact modules of Fig. 17 showing two modules wherein in each module a magnetic switch is coupled to active electronics to generate a unique transmitted signal indicating that a plate in a weight stack has been separated from an adjacent plate, in accordance with one embodiment of the present invention.

Fig. 22B illustrates a block diagram of a remote station sensor system for a weight machine in accordance with one embodiment of the present invention, wherein the sensor system has a plurality of wireless sensors/modules for determining the amount of weight lifted, and an ultrasonic range sensor to determine the speed and range of motion of the weight lifted.

Fig. 23 illustrates one example of a circuit for a module of Fig.

22A to transmit a unique signal in accordance with one embodiment of the present invention.

Fig. 24 illustrates an exemplary data packet format transmitted by the transmitter module shown in Fig. 23.

Fig. 25 illustrates a flow diagram of the operations performed by the transmitter, in accordance with one embodiment of the present invention.

Fig. 26 illustrates a flow diagram of the operations performed by the receiver for processing the data packet in accordance with one embodiment of the present invention.

Figs. 27-28 illustrate an exemplary layout of the non-contact active module in accordance with one embodiment of the present invention.

Fig. 29 illustrates an alternative embodiment of the non-contact active module utilizing a plurality of fiber optic light pipes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Fig. 1 shows a set of weight plates 40 arranged in a weight stack 42 on a exercise weight machine 44. The weight machine 44 has a frame 46, a set of parallel guides 48 for positioning the weight plates in the stack, a cable or set of cables 50, and a pin 52 for selecting the number of plates to be lifted.

In accordance with the present invention, a module 54 is mounted on each weight plate 40 of a weight machine, and the module 54 provides a signal which indicates that an adjacent plate has been lifted off the stack 42 of weight plates 40. Using the signal, a determination is made as to the amount of weight which has been lifted off the stack 42 during the exercise. This data can be used in determining and recording the user's exercise performance and history in a computerized fitness system.

In accordance with embodiments of the present invention, a set of modules 56 which forms an electrical circuit through physical contact between the modules is disclosed herein. Further, a set of non-contact modules which forms an electrical circuit without physical contact between the modules is also disclosed herein. The non-contact

modules include passive modules, such as modules formed using capacitance, or active modules which utilize low cost transmitters.

Referring to Fig. 1, a set of weight plates 40 of a weight machine is shown arranged in a stack 42. Each weight plate 40 in the stack can be provided with a module 54 which is mounted on the weight plate.

The module 54 interacts with the module mounted to the upper and lower adjacent weight plates. If the adjacent weight plate is lifted during exercise and separated from the corresponding weight plate, then the characteristics of the interaction between the modules 54 and mounted weight plates is altered, and accordingly the fact that the adjacent weight plate has been separated is detected. In particular, Fig. 1 illustrates a set of modules 56, each module 54 having a circuit element or electrical element 58 (i. e., a resistive element) connected across two conductive elements 60,62. Each of the conductive elements 60,62 has two electrical contacts 64,66,68,70 at opposing ends such that each module has four electrical contacts. When all the plates 40 are at rest in the weight stack 42, a circuit is formed between the modules such that the resistors 58 of the modules are connected in parallel to form an effective plate impedance or resistance, shown as Rp, defined herein to mean the equivalent impedance or resistance, for example, as seen looking into terminals 72,74.

In one example, a module 54 having an electrical element 58 therein is mounted to each weight plate 40 in the stack 42. At a fixed position at the bottom of the stack on the exercise weight machine, a module having a pair of contacts and a pair of terminals 72,74 is provided, and is positioned to be in contact the module of the bottom weight plate, so that the electrical characteristics of the circuit formed can be externally sensed.

If, for example, only the top plate is lifted, then a circuit is formed comprising the parallel combination of the electrical elements of the modules of the un-lifte lower plates. As a greater number of plates is lifted during different exercises, the corresponding effective plate impedance Rp as seen between the two terminals 72,74 changes depending upon the number of plates lifted during the exercise. When the exercise is completed, and the plates are returned to their resting position in the stack, the effective plate impedance Rp measured between the terminals 72,74 returns to the default value.

In one example, the determination of the amount of weight lifted is made by measuring effective electrical impedance of remaining modules that are not being lifted. The effective impedance is sensed and fed back to the electronics of a remote station, discussed below, where it is processed and then the appropriate weight lifted is displayed. For example, if the weight stack consists of twenty weight plates, each weighing ten pounds and each module has a 1-Mohm resistor in it, the electrical impedance Rp measured would be 50 Kohms (20 1-Mohm resistors in parallel). If the user lifted 8 weight plates or 80 pounds off the stack, the measured impedance Rp of the remaining 12 plates would be 83 Kohms (12 1-Mohm resistors in parallel).

It will be appreciated that the resistors 58 could be replaced with other circuit elements such as capacitors, inductors, diodes, transistors, etc., as the circuit element within the modules 54 which form the circuit.

If an electrical signal is applied to the circuit formed by the contacting modules 54, then the changes in the output signal of the network can be measured to determine the amount of weight lifted during an exercise, as will be discussed below. The modules 54 of the

present invention can be utilized with a sensor system for a weight machine for determining the amount of weight lifted. Fig. 2 illustrates a block diagram of a remote station sensor system 80 for a weight machine in accordance with one embodiment of the present invention.

The remote station 80 is adapted for use with a particular weight machine in the gym, such that each weight machine can be provided with an individual remote station.

As shown in Fig. 2, the remote station 80 has a microcontroller 82 has a keypad 84 for user input, a display 86 for displaying data or querying the user for input, a speaker 88 for providing audible feedback, and an RF transceiver 90 for communicating with a central kiosk, described below.

The microcontroller 82 has an analog-to-digital converter 92 for processing the signals provided by the modules 54 (or set of modules 56) of the present invention. Conventional signal conditioning 94 can be used to filter and amplify, as needed, the electrical signals generated by the modules 54 mounted on the plates 40 of the weight stack 42. The microcontroller 82 accesses a table stored in memory 96, preferably RAM, which maps the digital value of the signal received from the modules 54,56 to a weight value.

Further, an ultrasonic range sensor 98 is provided on the weight machine 44 which is typically mounted on the top of the frame 46 of the weight machine and measures the distance to the top plate of the weight stack. The microcontroller 82 can then calculate the range of motion and speed at which the weights are being moved by the user.

In one example, the ultrasonic range sensor 98 utilizes two ultrasonic transducers, a transmitter and a receiver. The transmitter sends, for example, a 40 kHz pulse train which reflects off of the top plate, and the reflection is detected by the ultrasonic receiver. The

microcontroller 82 calculates that the elapsed time in which the reflected pulse traveled from the transmitter to the receiver, and accordingly the distance (range of motion) as the weight is moved during exercise, is then calculated.

The microcontroller 82 is provided with a battery 100 and power management system 102. Once it is detected that one or more plates from the weight stack have begun to be lifted, the microcontroller 82 can begin its determination of the amount of weight being lifted (utilizing the signal from the modules 54,56), as well as the range of motion and speed of the repetitions being performed during exercise.

The remote station/stations 80 transmit the calculated data via the RF transceiver 90 to a central kiosk 110, shown in Fig. 3. In one example, the information is sent to the kiosk 110 via a wireless local area network (LAN) 111. The kiosk 110 stores personal workout profiles, and includes a built-in data backup system to ensure the integrity of all records stored thereon. In one example, the kiosk 110 includes a personal computer 112 having persistent storage 114, a modem 116 or network connection 118, so that data collecte on the central kiosk 110 can be transmitted to other computers in the network, such as over the internet.

At the kiosk 110, the data received is processed and stored, and can later be accessed by the user so that the user can view his or her progress. The kiosk 110 can employ a touch screen device or other input device for allowing the user to access different data screens presented at the kiosk. The kiosk 110 can also be provided with a printer so that a user can print the workout data.

In this manner, one embodiment of the system of the present invention can track and collect exercise information including, but not

limited to, the number of sets performed, the number of repetitions performed per set, the weight used in a particular set or exercise, the range of motion, and the speed at which repetitions were performed.

Referring to Fig. 4, and in accordance with one embodiment of the present invention, a resistive divider network 120, also known as a voltage divider network, is utilized with the effective plate impedance Rp (of Fig. 1) used in the voltage divider. A source voltage Vs, such as 3 volt dc, can be connected in series with a source resistor Rs, for example 5 Kohms, connected in series with the variable effective plate impedance Rp. The output voltage Vout can be measured by the analog-to-digital converter 92 of the microcomputer 82 across the effective plate impedance Rp. As the output voltage Vout changes, the microcontroller 82 can determine the particular plate or set of plates which have been lifted by the user during the exercise.

Fig. 5 illustrates an exemplary graph of the output voltages (shown as Vmeas) generated by the resistor divider 120 of Fig. 4 as the number of plates lifted changes. It can be seen that as different plates are lifted, the output voltage Vmeas changes discretely such that the microcontroller 82 (Fig. 2) can detect how many plates have been lifted. The graph of the output voltage Vmeas detected by the microcontroller will vary depending on the implementation, such as the values of the plate resistors and the source resistor of the voltage divider, along with the voltage of the source voltage used as the reference voltage Vs of the voltage divider).

The microcontroller 82 can be calibrated when the system is installed or initialized simply by requesting that a known amount of weight be lifted, and at that time, the microcontroller 82 can measure and store the output voltage Vout generated by the resistor

divider 120/effective plate impedance Rp of the modules. When all of the plates have been lifted and all of the data has been recorded permanently by the microcontroller 82, then the microcontroller 82 would have sufficient data, such as that shown in Fig. 5, to form a mapping of the various output voltages Vout corresponding to the number of plates lifted, in order to then determine the amount of weight lifted during a given exercise. Since the microcontroller 82 has non- volatile memory, calibration of the weight machine should be required only once during the life of the machine. Alternatively, if all of the electrical elements attached to the weight plates have the same value, then calibration can be performed by selectively lifting a portion of the weights in the stack and interpolating the effective impedance values provided when the remaining weight plates are lifted during exercise.

In another embodiment of the invention, the effective plate impedance Rp formed by the modules 54 mounted on the weight plates 40 can be used to vary the time constant of an oscillator circuit to alter the frequency (or duty cycle) of an oscillator circuit. Referring to Fig. 6, an oscillator circuit 130 producing an output frequency Fout is shown having a capacitor 132 and the effective plate impedance Rp coupled in parallel. As the effective plate impedance Rp changes due to a number of plates being lifted in the stack, the frequency or duty cycle (time duration) Fout of the oscillator circuit 130 is altered.

Fig. 7 illustrates an exemplary graph of the changes in the duty cycle of the output signal (shown as"Time") of the oscillator 130 of Fig. 6 as the number of plates lifted from the weight stack changes. As with the circuit of Fig. 4, the microcontroller 82 (Fig. 2) can be calibrated so that the microcontroller 82 accurately calculates the amount of weight lifted during an exercise based on the duty cycle of the oscillator output signal Fout.

As discussed above with reference to the embodiments utilizing physical contact between the modules 54 to complete an electrical circuit, a module is mounted on each plate of the weight machine.

Referring to Fig. 8A, the module 54 can be mounted on the sides of the weight plates 40, or on the end of the weight plates, depending upon the particular geometry of the weight machine. In one example, double-sided adhesive is used to mount the module 54 onto the plate.

For example, double-sided adhesive tape available from 3M Corp. has been found to be suitable under various operating conditions. The modules 54 can also be attached to the plates 40 by the use of adhesive, welding, soldering, fastening with screws, nails, or other fasteners.

The module 54 could also be fabricated directly into the weight plates during manufacture. Fig. 8B shows a single weight plate 140 with a set of conductors 142,144 positioned within two bores 146,148 in the weight plate, and an electrical element 150 coupled therebetween within a channel 152 formed in the weight plate. Each weight plate 140 could be manufactured in accordance with the structure shown in Fig. 8B. The ends of the conductors 142,144 electrically couple to an adjacent weight plate (not shown) when the weight plates are together in the stack.

Referring to Figs. 9-14, one embodiment of a module 160 is shown having a set of four contacts 162A, B, C, D mounted about a non-conductive housing 164. The housing 164 is generally rectangular in shape, and in one embodiment, it has a height dimension slightly smaller than the thickness of a weight plate. (See Fig. 15A.) The housing 164 has, on both its top and bottom portions 166,168, a rectangularly shaped slot or channel 170, as best seen in Figs. 9,10, 11,13 and 14. Referring to Fig. 11, along the top portion 166 of the

module, the contacts 162A, 162B are placed within the channel 170 and secured to the module using an electrically conductive pair of screws 172. A surface mount resistor 174 is soldered between the contacts 162A, 162B so that the resistance between the top pair of contacts 162A, 162B is governed by the value of the resistor 174. On the bottom side 168 of the housing 164, referring to Fig. 13, the contacts 162C, 162D are placed within the channel 170 and secured using a pair of bolts 176. Epoxy can be used to fill in the remaining area within the channel 170 on both the top side and bottom side to further ensure the integrity of the module.

Referring to Fig. 14, in one example, each of the contacts 162A, B, C, D has a substantially flat portion 178 which terminates at a flat end 180, and an opposing arcuate portion 182 which is adapted for electrically coupling with a contact of another adjacent module. In one example, the contacts 162A, B, C, D are made from a electrically conductive metallic material available from Acme Battery Co., part number 245.

The ends 180 of the contacts 162A, B, C, D along the flat portion 178 are positioned within the slot 170 of the module such that a non-conductive gap 184 is formed therebetween, as shown in Figs. 10, 13 and 14. In this manner, each module provides a parallel connection of a circuit element, such as a resistor 174, with the adjacent module when the contacts of two modules are in physical contact. As shown in Fig. 15A, the contacts 186 and 190, and 188 and 192, of adjacent modules 194,196 electrically couple one another when the plates of the weight stack are together. When the weight stack is not being lifted, all of the electrical components within the modules attached to the weight plates are connected in parallel.

Fig. 15B illustrates an alternative embodiment of the module of Figs. 9-15A wherein the contacts 200A, B are inwardly curved along the top side 202 of the module, and a pair of conductive plates 204, 206 are positioned along the bottom side 208 of the module. The conductive plates 204,206 are coupled to the conductors 200A, 200B of the module so that the electrical element (i. e., a resistor 208) is connected across the conductive plates 204,206 through conductive screws 210. The conductive plates 204,206 are sized so to facilitate a reliable electrical connection with the curved contacts 212A, B of the lower adjacent module when the weight plates are resting together in the stack.

Fig. 16 illustrates an alternative embodiment wherein the modules 210,212 are U-shaped and attached along the side or end of the weight plates 40. A flexible material 214 can be embedded with a pair of conductors 216,218 with two contacts 220A, B, C, D on each end of the conductors. The circuit element (i. e., resistor 222) is connected across the conductors 216,218 so that the circuit element is connected in parallel to the circuit element of the adjacent module when the weight plates are together in the stack. For instance, flexible PCB material can be used to form the module, with the contacts 220A, B, C, D between the modules formed by conductive areas along the PCB material.

Figs. 17-29 relate to alternative embodiments of module configurations, wherein adjacent modules do not physically contact each other, but the presence or absence of an adjacent weight plate and corresponding module is detectable by the system so that the weight being lifted can be determined. Fig. 17 shows two adjacent weight plates 230,232 having modules 234,236 mounted thereon which are not in contact with each other. An interruption of the

interaction between the modules 234,236, such as capacitance, inductance, magnetism, or optical beams or the like, is detected by the module and communicated to the microcontroller 82 (Fig. 3) which permits a determination of the weight being lifted.

Referring to Fig. 18, a module 240 which employs capacitive coupling is shown having a resistor 242 coupled across two conductors 244,246, each conductor having a capacitor plate 248A, B, C, D at both ends of the conductor. The capacitor plates 248A, B, C, D are positioned so that they will be aligned with the corresponding capacitor plates of an adjacent module, and will form an air gap capacitor between pairs of capacitor plates. Fig. 19 shows an example set of four modules 250A, B, C, D forming an RC network when the four weight plates 252A, B, C, D are together in the weight stack. The circuit can be excited using an AC signal across terminals 254,256 to measure the response of the RC network to the AC signal. As a different number of weight plates in the stack are lifted, the RC network's response to the AC signal changes, and the number of weight plates lifted can be determined. It is understood that different excitation signals can be used, such as a AC signal at a fixed frequency, a step or impulse signal, or the like. The response of the RC network to the excitation signal can be characterized as the changes in phase, amplitude, impedance, step or impulse response, etc.

Figs. 20-21 illustrate various characteristics of the air-gap capacitance formed between the capacitor plates of adjacent weight plates. It can be seen that as the gap between the capacitor plates of adjacent modules increases, the capacitance decreases. As weights are lifted from the stack, the change in capacitance of the circuit shown in Fig. 19 can be measured by the microcontroller 82 (Fig. 2) using

various techniques as described above. For example, the impedance measurement can be performed as previously described, where the effective impedance of all the plates in parallel is measured. It should be noted that this non-contact measurement approach could be implemented with inductive coupling as well.

Figs. 22-29 illustrate an alternative embodiment of the present invention wherein an active circuit (shown as 260 in Fig. 22A) is included in each module, and the modules detect the presence or absence of adjacent modules without the need for physical contact between modules. In the embodiments shown in Fig. 22-29, the modules are not physically coupled to the microcontroller 82 of the remote sensor station as previously shown in Fig. 2. Rather, each module transmits a unique signal (i. e., a wireless RF signal) to the microcontroller if an adjacent plate is not detected by the module.

Based on the signal received by the microcontroller, the weight lifted during exercise is determined.

Fig. 22B shows a block diagram of a remote station sensor system 270 for a weight machine in accordance with one embodiment of the present invention, wherein the sensor system has a plurality of wireless sensors/modules 272 for determining the amount of weight lifted, and an ultrasonic range sensor 274 to determine the speed and range of motion of the weight lifted. The microcontroller 276 receives the wireless signal from one of the modules 272 and decodes the unique signal to determine which module is sending the signal, and therefore determines which plates are being lifted.

Fig. 22A shows one embodiment of a module 272 which is capable of detecting the presence of an adjacent module 280 when the adjacent weight plate 282 is substantially adjacent to, or in close proximity to, the module 272 attached to weight plate 273. The

module 272 transmits a unique signal when the adjacent weight plate 282 is not in close proximity, indicating that the adjacent weight plate 282 has been lifted. Based on the unique signal transmitted and received by the microcontroller of the remote station (Fig. 22B), the microcontroller can then determine the amount of weight being lifted.

In the example shown in Fig. 22A, each weight plate 273,282 is provided with a module 272,280, respectively, with a magnet 284A, B, a magnetic switch 286A, B (i. e., a reed switch), and transmitting electronics 288A, B, including a transmitter section 290A, B and an antenna 292A, B. Determining whether the adjacent plate 282 is in close proximity to module 272 can be achieved by using a magnet 284 and reed switch 286. The magnet 284A, B is positioned at the bottom of each module 272,280 and the reed switch 286A, B is mounted near the top of the respective module so that when there is no gap between adjacent weight plates 273,282, the magnetic field from the magnet 284B causes the reed switch 286A to close. The battery 294A, B in the module supplies power to the electronics 288A, B, respectively. When the weight plates separate, the reed switch 286A opens, which turns-on the transmitter 290A in the lower plate module 272 which sends out a unique identification code to a receiver 300 coupled to microcontroller 276 in the remote sensor station 270 of Fig. 22B. The microcontroller 276 of the remote sensor station decodes the signal and then displays the appropriate weight lifted value on the display 302.

Sensing the adjacent plate can be performed by a variety of sensing means, in place of the magnet/reed switch 286A, B. For example, a Hall effect device, or capacitive, inductive, eddy current, optical (passive or active), RF sensors could be used. Electrical

contacts between modules, for example as described above, could also be employed.

Each module is provided with transmitting electronics which inclue, in one example, a low cost microcontroller or processor coupled to an RF section. Fig. 23 illustrates one example of a circuit 310 for the module 272 or 280 of Fig. 22A to transmit a unique signal in accordance with one embodiment of the present invention. In the example of Fig. 23, the microcontroller 312 is provided with a 3.5 v battery 314, and the microcontroller 312 operates in a very low power sleep mode (wherein the processor's internal oscillator and other internal sections are shut down) until an interrupt is received from the reed switch 316. In this example, when the magnet of the adjacent weight plate is positioned near the reed switch 316 (i. e., when the weight plates are together in the stack), the reed switch 316 is closed which provides a low signal into)/0 pin GP2 (shown as pin 5) of the processor 312. When the reed switch 316 is separated from the magnetic field of the magnet of the adjacent weight plate, the switch 316 opens and an interrupt (a high logic signal) is generated on pin GP2 which awakes the processor 312. After a delay period, described below, the processor 312 transmits a unique signal, through the transmit circuitry 318, which is received and decoded by the remote station 270 (Fig. 228) to determine the amount of weight lifted.

The processor 312 shown in Fig. 23 is, in one example, a one- time-programmable low cost microcontroller. A unique identification code, which is transmitted as part of the unique signal sent by the module, can be assigned as one value of a 16 bit code. The ID code can be serialized in production (approximately 64,000 unique 16 bit codes would exist) so that each module is assigned a unique code

which would not conflict with a code from another module in the gym or fitness facility.

The transmit circuit section 318 is shown in Fig. 23 is adapted for a 418 MHz carrier frequency. The signal is an RF signal suitable for transmission through an antenna 320.

The microcontroller 312 is programmed to send a serial bit pattern (i. e., 16 bits). In one example shown in Fig. 24, each modules transmits a unique signal 330 which includes a preamble 332, a unique plate identification 334 corresponding to the weight plate to which the module is coupled, and a check sum 336. It is understood that other data fields, formats, or encoding could be employed depending on the particular implementation. Simple error detection and correction encoding techniques could be used as well. In one example, on/off keying is used to modulate the transmitted signal 330. Different modulation techniques could also be employed.

Further, many types of communication types and systems can be employed. Any frequency of electro-magnetic energy could be used including but not limited to light, infrared, radio and magnetic coupling.

Fig. 25 illustrates a flow diagram of the operations performed by the module's transmitter. In one example, the reed switch is configured to open and start the microcontroller of the module when an adjacent weight plate is removed as described with reference to Fig. 23. At operation 340, the microcontroller initializes from a sleep state and begins a wait/delay timer for a delay period. The delay period is provided to prevent the module from sending an errant signal to the remote sensor station 270 of Fig. 22B, if for instance, the adjacent plate bounces against the module's weight plate when the weight stack is dropped by the user during exercise. In one example, the delay

period is 20 milli-seconds. After the delay period has expired, control is passed to operation 342 which sends the modules unique message 330 to the remote sensor station of Fig. 22B. Operation 344 then delays for a random amount of time, and control is returned to operation 342 for re-transmitting the same message 330 again to the remote sensor station of Fig. 22B. In this manner, the likelihood of collisions with other messages being sent by modules of other weight machines in the gym/fitness facility is reduced. This message 330 is re-transmitted until the adjacent weight plate is positioned next to the module's weight plate, and the reed switch closes which stops the module's microcontroller into a very low power sleep mode.

Fig. 26 illustrates a flow diagram of the operations performed by the microcontroller 276 of the remote sensor station 270 of Fig. 22B for processing the received data packet 330. At operation 350, the microcontroller 276 of the remote sensor station 270 of Fig. 22B retrieves the data from the received message 330, and at operation 352, matches the ID code from the message 330 with a set of ID codes stored in the microcontroller 276. Decision operation 354 determines if there is a match, and if so, operation 356 displays the amount of weight being lifted. Operation 356 also stores the value of the weight being lifted, along with other data including the range of motion and the speed at which the weight was lifted as measured by sensor 274 (Fig. 22B).

The set of ID codes stored in the microcontroller 276 can be established by a one-time calibration technique wherein during set-up, a menu on the remote sensor station 270 of Fig. 22B directs a user or system administrator to lift each weight in the stack in a particular order. As each weight is lifted under the direction of the remote sensor station, the microcontroller 276 of the remote sensor station stores the

ID of the message received as sent by the module attached to the weight plate, and stores a table in non-volatile memory mapping the unique ID to a weight plate and a weight amount. Once this calibration for each plate is completed, the microcontroller 276 of the remote sensor station can easily determine at operations 352,354,356 how much weight is being lifted during an exercise based on the received messages.

Figs. 27-28 illustrate an exemplary layout of the module 360 showing the placement of the magnet 362 along one edge 364 of the module, and the reed switch 366 along the opposing edge 368 of the module 360.

Alternatively, RFID (Radio Frequency Identification) techniques could be implemented in each module. In the RFID system, the remote sensor station 270 of Fig. 22B sends out an high-power RF signal which is received by all the modules. The RF energy from the RF signal provides power to each of the modules and activates a transmitter in any module whose reed switch is not detecting the presence of the magnet of an adjacent weight plate module. The transmitter in that module then sends a unique signal to the remote sensor station, and based on the unique signal, the remote sensor station 270 determines which weight plate has been lifted. In one example of a module, RFID techniques are employed which allow the modules to operate without batteries, which therefore reduces the need for maintenance of the modules over the life of the modules.

Fig. 29 illustrates an alternative embodiment of the non-contact active module 370A, B utilizing a plurality of fiber optic light pipes 372A, B. In this embodiment, light is passed between adjace

station 270, and decodes the transmitted signal to determine how much weight has been lifted. Alternatively, each module can transmit a unique infrared (IR) signal to an IR receiver located at the remote station, in a manner similar to that described with reference to Figs. 22- 26.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various other changes in the form and details may be made without departing from the spirit and scope of the invention.