IL96040A - Data transmission system - Google Patents

Description

DATA TRANSMISSION SYSTEM ILID PTY.LTD.

The present invention relates to a data transmission system and more particularly to a data transmission system suitable for use, for example, in transmitting pricing data to electronic shelf labels in retail stores, such as supermarket's, and for displaying the data. Of course it will be appreciated that the invention may be used in any situation wherein data is transmitted to many different locations remote from a central base station and has particular utility where the data is frequently changing. For example the invention could be used in building paging systems or in warehousing, for inventory control.

A number of electrical or electronic systems have been proposed in the past for providing warehouse and supermarket shelf labels. Such systems of course considerably reduce or eliminate the labour coats associated with maintaining and up-dating shelf labels and because of their expediency, reduce financial loss due to price change lags. Thus the known electrical or electronic systems provide considerable advantage but unfortunately they also introduce some technical problems. For example, any system which requires direct wiring is expensive to install and considerably reduces the flexibility of moving and re-arrangi g shelves which is a common practice in supermarkets.

Another system which has been proposed uses radio broadcasts to send radio frequency (r.f,) signals to up-date information of electronic shelf labels (modules). This sytem overcomes the problem of connecting wires but requires a battery to power each module and an antenna at each module to transmit and receive the r.f. signal. lpsspe.015/ilid Both these requirements ere likely to introduce obstacles which may stand in the way of widespread acceptance of the system in supermarket environments. Firstly the battery will require replacement from time to time which, in a typical store having say 6000 modules, would be a time-consuming and costl exercise. Furthermore, whatever type of miniature antenna is used it is likely that areas of poor transmission/reception will be encountered and this would detract from the overall performance and acceptability of the system. The requirement for the Installation of transmitter antenna throughout the store also means that this system does not totally eliminate store wiring. A system using r.f. transmission requires also, approval ,of the authorities controlling r.f. transmission and this creates a further inconvenience and possible delay at the outset.

Accordingly, it is an object of this invention to provide an improved data transmission system which obviates one ore more of the aforementioned problems of the known systems or suoh a system which at least provides a useful alternative.

The invention therefore provides a simplex data transmission system including a plurality of discrete modules each containing an LCD, display and being capable of receiving and displaying information, a control unit remote from said modules for generating data relevant to said information, a modulator connected to said control unit for modulating said data with signals to be transmitted, and electric lighting in the environment of said modules, characterized in that, said modulator Is connected in t fi filfifitrifi supply to. fifiin* filfintrin lighting an as tn modulate said supply with a low frequency data information signal containing address information and data whereby the transmitted light contains said data information signal, and each module incorporates a battery for providing operating power to the module and a photo detector whereby said data information signal is obtained by said modules from the electric lighting of the environment, and said address Information is transmitted at regular* intervals tu each module and each module incorporates a timer for timing the interval between receipt of the transmitted address of a particular module, said Another form of the invention provides a method of transmitting data to discrete modules from a remote central control unit, which modules are in an environment illuminated by electric lighting and wherein a modulator is connected to said control .. unit for modulating a main signal with said data, characterized in that, said main signal is the electric power supply to said lighting and said modules include a battery to provide operating power to the module and a photo-detector and said method comprises modulating said power supply with a low frequency encoded data signal containing address information of specific modules, detecting light from said electric lighting by said phto detector of each module and decoding said data signal at each module to determine by means of said address information which module/s accept said data.

In order that the invention may be more readily understood a particular embodiment will now be described with reference to the accompanying drawings wherein: Figure 1 is a basic circuit block diagram of an electronic supermarket shelf label pricing system according to the invention; Figure 2 is a schematic front elevation of a shelf label device according to the invention; Figure 3 is a circuit block diagram of the shelf label device of Figure 2; Figure 4 shows various graphs of the modulation waveform; Figure 5 is a circuit block diagram of the control logic within each shelf label; Figure 6 is a circuit block diagram showing in more detail the power modulator 10 used in the system of Figure 1; Figure 7 is a circuit block diagram showing in more detail the signal shaping/demodulator circuit 21 shown i Figure 5; Figure 8 is a vector diagram showing the phase modulation of the power source; and Figure 9 is a pictorial representation (not to scale) of a LCD display of a shelf label of the system showing the information it would display.

Referring now to the drawings and in particular Figure 1, there is shown a modulator 10 which receives power on connection 11 from the mains supply. A control unit 12, which consists of a microprocessor and associated logic converts data from a host such as a modem, instore computer or point of sale controller into a format suitable to drive the modulator 10. This data would normally, be received by the RS232 port of control unit 12. The output of modulator 10 is connected to artificial lighting in a building which; in this case is fluorescent lamps 13.

When the fluorescent lamps 13 are activated by the modulated, supply light emitted therefrom is incident upon shelf label devices 14 of which only 4 are shown in Figure 1. The control unit 12 receives information relevant to the price of various goods of/ the Ipsspe.015/ilid store and this information is provided to the modulator 10 which provides a modulated signal incorporating such pricing information. Thus the light emitted from the fluorescent lamps 13 is modulated with a signal containing various information including the address of the shelf label or labels to which the particular price applies and information as to the price. In a cycle of operation all shelf labels in a. store are addressed and current or up-dated information relevant to the article price is transmitted. Clearly there may be several labels which apply to the same item./ In this instance a table which would be maintained either within the host computer or control unit 12 would indicate which labels (by label address) have been allocated to a particular item.

Referring no to Figure 2, a shelf label device 14 is shown in more detail. It can be seen that a shelf label device includes a photo transistor 15, a solar cell 16 and a liquid crystal display 17, Light from the fluorescent lamps 13 is incident upon the photo transisto 15.

Referring now to Figure 3, a circuit block diagram of the shelf label device 14 is shown. The solar cell 16 is connected to a backup battery 18 and to a control logic circuit 19. The photo transistor 15 is connected to control logic circuit 19 and the output of the control logic circuit is connected to the LCD display 17. It will be noted that light from the fluorescent lamps is also incident upon the solar cell 16 to provide operating power to th shelf label device.

It will be evident from the description hereinabove that the power going to the building's lighting - system is modulated with lo I sspe.0l5/ilid 90 4 12 - 7 - 96040/2 frequency data information .Throughout this specification the term "low frequency" is intended to mean a frequency of the same order of magnitude as the frequency of the power signal of the artificial lighting system which is ususally less than 100 H2. This causes the lighting to transmit: information to the photo detectors of the shelf label devices. This information is then decoded and used to drive the LCD display 17 of each shelf label device 14.

Figure 4 shows graphs of various waveforms as they would be observed around the modulator 10 and within the shelf label 14. Waveform 29 is the 240 volt input power 11 to the modulator 10. Waveform 30 is the data for the shelf labels 14 which has been synchronized with the incoming mains power 29. Waveform 31 which has had the modulation of waveform 30 applied in the form of a phase shift is now added to mains power 29 to produce waveform 32 which is fed to the lighting 13. Waveform 33 is the signal detected by the photo detector 15 and used to produce waveform 34 which is a signal in recognition of a short cycle caused by a phase shift. Conversely waveform 35 is a signal in recognition of a long cycle caused by a phase shift. Waveform 36 is the decoded data produced by a set/reset flip flop the inputs of which are 35 and 34, respectively. This decoded data is fed to ,an Application Specific Integrated Circuit 20, (ASIC) (see Figure 5).

Figure 5 shows details of the control unit 19 within a label device 14. The unit 19 consists of the ASIC 20 with an oscillator 25 to control its speed of operation. The signal 33 from the photodector 15 is passed through shaping/demodulation circuitry 21 to remove glitches and digital input into the serial input of the ASIC 20. _ g _ 96040/2 information that the label must hold- It also contains LCD display drivers (not shown) which are used to drive the LCD directly (not in a multiplexed format) so as to achieve maximum contrast. The power tor the control circuitry is derived by feeding the voltage from a rechargable battery 18 through a current limiting resistor 26.

Figure 6 provides a more detailed circuit diagram of the modulator 10. The various waveforms shown in Figure 4 appear on connections in Figure 6 which are labelled with the corresponding reference* The modulator uses the phase shift voltage 31 to produce small amounts of change in the cycle length of the mains power being applied to the lighting 13. As the current through the f luoroscent tubes i s approximately ninety degrees out of phase with the voltage, the peak 1 ightpulse(signal 33) occurs at the zero voltage crossover. By moving the light power peak the data is easily detected but the data transmission, or the effect it has on the lighting, is barely visible to the human eye. In this way the data transmission is barely visible to the human eye. The modulator 10 has its own internal power supplies(not shown) to produce the + 5 volts required by the digital circuitry and 1/- 15 volts required by analog circuitry(bus 45). As well the power supply produces a +/- 140 volt bus 44 to supply power to power amplifier 43. The mains power pulses an connection 38 (normally 50 or 60 Hertz) are used to synchronize the phase shift changes of 90 degrees produced by phase shifter 41 with the incoming data 30 to drive an electronic switch 42 which in turn drives switch mode power amplifier 43. The power amplifier adds this modulation to the mains producing waveform 32 suitable for driving the lighting 13.

The actual degree of modulation is represented in Figure 8 where the mains voltage 29 h as a modulation voltage 31 applied in a positive and negative direction. Thus the peak phase — 2 a retan (vm vi) If the mains voltage is 240 volts (VI-240 ) when a phase shift voltage of 60 volts (vm=<50) is applied then the peak to peak ase modulation would = 28 degrees.

Referring to Figure 7 the decoder circuitry 21 of the label 14 detects this phase s ft. by having a ripple detector ci c it 22 which basically consists of a digital counter- This counter counts a number of counts for each half cycle of the mains and by using a long/short cycle detector 23 produces a "long Cycle" pulse for every long cycle and a "short cycle" pulse for every short cycle. These pulses are used to drive the set and reset inputs of RS flip flop 27 to decode the transmitted data.

The data is hroadcast to all lighting in the area as each label has its own identity code to allow it to detect which data is valid for its own particular purpose. As all the labels 1 are delivered without a predetermined address the labels are normally installed to the shelf stripping and then have a specific address downloaded into them by a portable handheld computer which has a special adaptor which allows the handheld computer to modulate a specific label's photo detector without affecting any other label. Once a label has received its address it is possible to set a flag within the label so that it will not accept data or instructions from the handheld computer until this flag is reset through the lighting system.

As the data flowing to the labels is simplex in that they cannot 96040/2

Claims (6)

1. A simplex data transmission system including a plurality of discrete modules each containing an LCD display and being capable of receiving and displaying information, a control unit remote from said modules for generating data relevant to said information, a modulator connected to said control unit for modulating said data with signals to oe transmitted, and electric lighting in the environment of said modules, characterized in that, said modulator is connected in Ihfi filRfitrln .supply in .said filfir.trin lighting an as tn mndi.ilate said supply with a low frequency data information signal containing address information and data whereby the transmitted light contains said data information signal, and each module incorporates a battery for providing operating power to the module and a photo detector whereby said data information signal is obtained by said modules from the electric lighting of the environment, and said address Information is transmitted at egula intervals to each module and each module incorporates a timer for timing the interval between receipt of the transmitted address of a particular module, said timer is adjustable to a predetermined time setting and in the event that said address is not received within said predetermined time said module is adapted to visually signal a possible error in the module by flashing its LCD display.

2. A data transmission system as defined in claim 1 , characterised in that, said system is a product price labelling system and said modules comprise shelf labels.

3. A data transmission system as defined in claim 2, wherein each said module contains an Integrated circuit for holding information required to be held by the module, and LCD display drivers for driving directly the LCD display of the module.

4. A data transmission system as defined in claim 3, wherein said information comprises item price information and other information relevant to the storage and sale of the item.

5. A method of transmitting data to discrete modules from a remote central control unit, which modules are in an environment illuminated by electric lighting and wherein a modulator is connected to said control unit for modulating a main signal with said data, characterized In that, said main signal is the electric - 11 - 96040/3 power supply to said lighting and said modules include a battery to provide operating power to the module and a photo-detector and said method comprises modulating said power supply with a low frequency encoded data signal containing address information of specific modules , detecting light from said electric lighting by said photo detector of each module and decoding said data signal at each module to determine by means of said address information which modules accept said data comprising as further step transmitting said address information at regular intervals to each module , timing the duration between receipt of successive transmission of said address data at each module and causing a display of the module to revert to a flashing mode in the event that the address data of a module is not received with a predetermined time delay, to indicate a communications or module fault.

6. A method as defined in claim 5, characterized in that , said modulating of said power supply with an encoded data signal is achieved using phase modulation. (• OR THE APPLICANT. Dr. Ytzhdk Hess