Two-way AC power line communications system

• US 4,429,299 A
• Filed: 01/26/1981
• Issued: 01/31/1984
• Est. Priority Date: 01/05/1979
• Status: Expired due to Fees

• Current Assignee: Robertshaw Controls Company (Schneider Electric SE)
• Original Assignee: Robertshaw Controls Company (Schneider Electric SE)
• Inventors: Kabat, Jules M., Beggs, James H.
• Primary Examiner(s): Groody, James J.
• Application Number:
  US06/228,608
• Time in Patent Office: 1,100 Days
• Field of Search: 340/310 R, 340/310 A, 340/505, 340/310 CP, 340/538, 340/870.01, 340/825.26, 340/825.52, 340/870.02, 340/870.03, 364/200, 364/900, 307/3, 307/140, 455/282, 455/352
• US Class Current: 340/4.21
• CPC Class Codes: G05B 2219/21034 Address I-O
• CPC Class Codes: G05B 2219/25178 Serial communication, data, also repeater
• CPC Class Codes: G05B 2219/25188 Superposition high frequency data signal on power lines, current carrier
• CPC Class Codes: G05D 23/1905 associated with tele control
• CPC Class Codes: G08B 19/00 Alarms responsive to two or more different undesired or abnormal conditions, e.g. burglary and fire, abnormal temperature and abnormal rate of flow
• CPC Class Codes: G08B 26/00 Alarm systems in which substations are interrogated in succession by a central station
• CPC Class Codes: H04B 2203/5458 Monitor sensor; Alarm systems
• CPC Class Codes: H04B 3/54 Systems for transmission via power distribution lines

Abstract

An AC power line communications system includes means for transmitting data to and receiving data from a plurality of transceivers over a conventional AC power distribution network. A central procession unit is provided to poll a plurality of room control units which are placed in each room or designated area of a hotel, hospital or building complex. The central processing unit conducts this polling sequence by periodically transmitting, over the neutral and ground lines of the power distribution network, and interrogation signal having an address portion and a data portion. Each room control unit is arranged to receive the interrogation signal and to compare the address portion of this signal with an address previously programmed into the unit. If the address portion of the interrogation signal corresponds with the programmed address of the room control unit, the unit transmits a return signal to the central processing unit. The room control units uses the data portion of the interrogation signal to report a number of different features of functions within the room (or area) in which the room control unit is located. A sequence of successive, identical addresses is used to allow the room control unit to accept data from the central processor. The central processing unit processes the data contained in the return signal insuring that the data received by the room control unit coincides wih the data transmitted to it by the central processing unit and permitting a record of the data accumulated by the room control unit to be made.

This AC power line communications system is well suited to be used in combination with a room status indicating system to monitor the status of each room in buildings such as a hotel, motel, or hospital complex, to monitor the condition of a smoke detector located in each room of the complex, to remotely control the operation of the heating and cooling equipment in each room of the complex, to convey message-waiting information to each room in the complex and to perform an automatic wake-up operation.

Claims

1. A two way data transmission communication system for effecting two way transmission of data on an AC power line which has interferring noise thereon and which is located within a building or building complex comprising:

a plurality of transceivers each of which is located in a different room or area of said building or building complex and connected to said AC power line for transmitting data between the transceivers each of said transceivers having a transmit mode and a receive mode during the operation thereof, each of said transceivers further having;

(1) a receiver means for detecting address signals transmitted over the neutral and ground of the AC power line associated with said building or building complex;

(2) means for accumulating data from various external sources;

(3) transmitter means for transmitting a return signal over the neutral and ground of said AC power line, said return signal being representative of the data accumulated by said transceiver;

(4) means for initiating transmission of said return signal upon receipt of a preselected address signal, said system further including a central processing unit having

means for selectively polling each of said transceivers by transmitting over the neutral and ground of said AC power line an address signal which is representative of the transceiver being polled,

receiver means for detecting return signals transmitted over the neutral and ground of said AC power line; and

means for processing said return signals.

2. The system as in claim 1 wherein the transmitter means associated with each of said transceivers is comprised of a tri-state switching device having three independent switch states comprising a first switch state wherein said tri-state switching device presents a high impedance to the neutral line of said AC power line, a second switch state wherein said tri-state switching device couples a first voltage with the neutral line of said AC power line, and a third switch state wherein said tri-state switching device couples a second voltage with the neutral line of said AC power line, said tri-state switching device being operable to assume one of these three switch states in response to the condition of a transmitter control signal provided to it, and means for generating said transmitter control signal from the data accumulated by said transceiver.

3. The invention as in claim 2 wherein said system includes a filtering means for coupling said second voltage to said neutral line.

4. The system as in claim 3 wherein said filter means is a series resonant filter.

5. The system as in claim 2 wherein said tri-state switching device is comprised of an NPN switching transistor and a PNP switching transistor, each switching transistor having its collector terminal electrically coupled with the neutral line of said AC power line and its base terminal arranged to accept said transmitter control signal, said PNP switching transistor having its emitter terminal electrically coupled with a first voltage, and said NPN switching transistor having its emitter terminal electrically coupled with a second voltage, said first voltage being of a higher voltage than said second voltage.

6. The system as in claim 2 wherein said means for generating said transmitter control signal from the data accumulated by said transceiver is comprised of means for producing a frequency modulate output signal having a frequency representative of the data accumulated by said transceiver.

7. The system as in claim 1 wherein said central processing unit includes means for transmitting a synchronization signal over the neutral and ground of said AC power line.

8. The system as in claim 7 wherein each of said transceivers includes means for synchronizing the operation of each of said transceivers with the operation of said central processing unit such that each of said transceivers is in condition to receive address signals only during the time period during which said central processing unit is actually transmitting address signals.

9. The system as in claim 8 wherein said synchronizing means is comprised of

means for deriving a clocking signal from a 60 Hz AC power signal normally present on said AC power line, said clocking signal having an established phase relationship with said 60 HZ AC power signal,

means for detecting the transmission of a synchronization signal by said central processing unit over the neutral and ground of said AC power line, said detecting means being operable to produce a disabling signal as long as a synchronization signal is being received from said central processing unit, and

counting means for periodically establishing a time period during which said transceiver is in condition to receive address signals, said counting means being operable to maintain a reset condition in response to said disabling signal.

10. The system as in claim 1 wherein the processing means associated with said central processing unit is comprised of means for storing the data contained in said return signals and means for correlating said retrieving data from said storing means to thereby provide a display of said data.

11. The system as in claim 1 wherein the processing means associated with said central processing unit is comprised of

memory means for storing the data provided to said central processing unit by said return signals, said memory means being operable to selectively store and retrieve data pertaining to each of said transceivers,

means for comparing the data provided to said central processing unit by a first return signal from a first transceiver with the stored data pertaining to said first transceiver,

means for initiating the transmission of an address signal which is representative of a second transceiver if the data provided to said central processing unit by said first return signal coincides with the stored data pertaining to said first transceiver,

means for initiating the transmission of an address signal which is representative of said first transceiver if the data provided to said central processing unit by said first return signal does not coincide with the stored data pertaining to said first transceiver,

means for comparing the data provided to said central processing unit by a second return signal from said first transceiver with the stored data pertaining to said first transceiver,

means for initiating the transmission of an address signal representative of a second transceiver if the data provided to said central processing unit by said second return signal coincides with the stored data pertaining to said first transceiver,

means for comparing the data provided to said central processing unit by said first return signal with the data provided to said central processing unit by said second return signal if the data transmitted to said central processing unit by said second return signal does not coincide with the stored data pertaining to said first transceiver,

means for using the data provided to said central processing unit by one of the two return signals from said first transceiver to update the stored data pertaining to said first transceiver if the data provided to said central processing unit by said first return signal coincides with the data provided to said central processing unit by said second return signal, and

means for initiating the transmission of an address signal which is representative of a second transceiver once the stored data pertaining to said first transceiver has been updated.

12. The system as in claim 11 wherein the processing means associated with said central processing unit includes means for providing an indication that a particular transceiver is not operating properly if the data provided to said central processing unit by two consdective return signals from said particular transceiver does not coincide.

13. The combination system as in claim 1 including means for effecting high impedance at each transceiver input across the neutral and ground of the AC power line during the receive mode.

14. The system as in claim 1 including means for effecting a low impedance at each transceiver input across a neutral and ground of the AC power line during the transmit mode.

15. An AC power line communications system for transmitting digital information to and from separate locations or areas on an AC power line which may have interferring noise thereon and which is located within a building or building complex, said digital information capable of being reliably used upon receipt at many locations, said system comprising:

a central processing unit having

receiving means for accumulating information and memory means for storing information pertaining to a particular location or area;

said central processing unit also including a

transmitting means for transmitting an interrogation signal to said particular location or area over the neutral and ground of an AC power distribution network associated with said location or area, said interrogation signal having an address portion which is representative of said particular location or area and an information portion which is representative of the information pertaining to said particular location or area;

a plurality of transceivers each of which is located in a different location or area, each of said transceivers having

means for receiving interrogation signals transmitted by said central processing unit;

means for transmitting digital information to said central processing unit; and

means for accepting the information portion of a received interrogation signal if the address portion of said received interrogation signal is representative of the particular location or area in which said transceiver is located.

16. The system as in claim 15 wherein each of said transceivers includes a counting means for recording the number of consecutive received interrogation signals having an address portion representative of the particular room or area in which that transceiver is located, said counting means being operable to have its count state incremented a set amount upon receipt of an interrogation signal having an address portion which is representative of the particular location or area in which that transceiver is located and to have its count state reset to a preselected count state upon receipt of an interrogation signal having an address portion which is not representative of the particular location or area in which that transceiver is located and means for causing the data transmitted to said transceiver by the information portion of one of said consecutive interrogation signals to be stored in said memory means in response to said counting means obtaining a preselected count state.

17. The system as in claim 15 wherein each of said transceivers includes means for synchronizing the operation of each of said transceivers with the operation of said central processing unit such that each of said transceivers is in condition to receive interrogation signals only during the time period during which said central processing is actually transmitting interrogation signals.

18. The system as in claim 17 wherein said central processing unit includes means for transmitting a synchronization signal over the neutral and ground of said AC power line.

19. The system as in claim 18 wherein said synchronizing means is comprised of

means for deriving a timing signal from a 60 HZ AC power signal normally present on said AC power line, said timing signal having an established phase relationship with said 60 Hz AC power signal,

means for detecting the transmission of a synchronization signal by said central processing unit over the neutral and ground of said AC power line, siad detecting means being operable to produce a disabling signal as long as a synchronization signal is being received from said central processing unit, and

counting means for periodically establishing a time period during which each of said transceivers is in condition to receive address signals, said counting means being operable to maintain a reset condition in response to said disabling signal.

20. The system as in claim 15 wherein each of said transceivers includes

memory means for storing the data provided to a transceiver by the information portion of an interrogation signal,

counting means for recording the number of consecutive received interrogation signals having an address portion which is representative of the particular location or area in which said transceiver is located, said counting means being arranged to have its count state incremented by a set amount upon receipt of an interrogation signal having an address portion which is representative of the particular location or area in which said transceiver is located to have its count state reset to a preselected count state upon receipt of an interrogation signal having an address portion which is not representative of the particular location or area in which said transceiver is located, and

means for causing the data provided to said transceiver by the information portion of one of said consecutive interrogation signals to be stored in said memory means in response to said counting means obtaining a preselected count state.

21. The system as in claim 20 wherein each of said transceivers includes means for accumulating data from various external sources.

22. The system as in claim 21 wherein each of said transceivers includes transmitting means for transmitting a first return signal over the neutral and ground of said AC power line, said return signal being representative of the data accumulated by a transceiver and of at least a portion of the data stored within said memory means of said transceiver, and means for initiating tranmission of said return signal upon receipt of a interrogation signal having an address portion which is representative of the particular transceiver location or area.

23. The system as in claim 22 wherein the transmitter means associated with each of said transceivers is comprised of a tri-state switching device having three independent switch states comprising a first switch state wherein said tri-state switching device presents a high impedance to the neutral line of said AC power line, a second switch state wherein said tri-state switching device couples a first voltage with the neutral line of said AC power line, and a third switch state wherein said tri-state switching device couples a second voltage with the neutral line of said AC power line, said tri-state switching device being operable to assume one of these three switch states in response to the condition of a transmitter control signal provided to it, and means for generating said transmitter control signal from the data accumulated by said transceiver and from at least a portion of the data stored within said memory means.

24. The system as in claim 23 wherein said tri-state switching device is comprised of an NPN switching transistor and a PNP switching transistor, each switching transistor having its collector terminal electrically coupled with the neutral line of said AC power line and its base terminal electrically coupled with a common input terminal which is arranged to accept said transmitter control signal, said PNP switching transistor having its emitter terminal electrically coupled with a first voltage, and said NPN switching transistor having its emitter terminal electrically coupled with a second voltage, said first voltage being of a higher voltage than said second voltage.

25. The system as in claim 24 wherein said means for generating said transmitter control signal from the data accumulated by said transceiver is comprised of means for producing a frequency modulated output signal having a frequency representative of the data accumulated by said transceiver.

26. The system as in claim 22 wherein said transmitting means of each transceiver will transmit a second return signal, and wherein said central processing unit includes

memory means for storing the data provided to said central processing unit by said return signals and by other system data sources, said memory means being operable to selectively store and retrieve data pertaining to each location or area within said locations or areas,

means for comparing the data transferred to said central processing unit by said first return signal from a first transceiver with the stored data pertaining to said first transceiver,

means for initiating the transmission of an interrogation signal having an address portion representative of a second transceiver if the data provided to said central processing unit by said first return signal coincides with the stored data pertaining to said first transceiver,

means for initiating the transmission of an interrogation signal having an address portion representative of said first transceiver if the data provided to said central processing unit by said first return signal does not coincide with the stored data pertaining to said first transceiver,

means for comparing the data thereby provided to said central processing unit by said second return signal from said first transceiver with the stored data pertaining to said first transceiver,

means for initiating the transmission of an interrogation signal having an address portion representative of a second transceiver if the data provided to said central processing unit by said second return signal coincides with the stored data pertaining to said first transceiver,

means for comparing the data provided by said first return signal with the data provided by said second return signal if the data provided to said central processing unit by said second return signal does not coincide with the stored data pertaining to said first transceiver,

means for interpreting the difference between the data provided to said central processing unit by said first and second return signals and the stored data pertaining to said first transceiver if the data provided to said central processing unit by said first return signal coincides with the data provided to said central processing unit by said second return signal.

27. The system as in claim 26 wherein said central processing unit includes means for using the data provided to said central processing unit by one of said two return signals to update the stored data pertaining to said first transceiver if the difference in the data provided to said central processing unit by said first and second return signals and the stored data pertaining to said first transceiver is interpreted by said interpreting means as accumulated from said first transceiver, and means for initiating the transmission of an interrogation signal having an address portion representative of a second transceiver once the stored data pertaining to said first transceiver has been updated.

28. The system as in claim 26 wherein said central processing unit includes means for causing a preselected number of interrogation signals having an address portion representative of said first transceiver to be transmitted consecutively if the difference in the data provided to said central processing unit by said first and second return signals and the stored data pertaining to said first transceiver is interpreted by said interpreting means as requiring transceiver output change by said central processing unit, means for comparing the data provided to said central processing unit by each return signal in response to each of said consecutive interrogation signals with the stored data pertaining to said first transceiver, and means for initiating the transmission of an interrogation signal having an address portion representative of a second transceiver if the data provided to said central processing unit by either of said return signals coincides with the stored data pertaining to said first transceiver.

29. The system as in claim 26 wherein the said central processing unit includes means for providing an indication that a particular transceiver is not operating properly if the data provided to said central processing unit by two consecutive return signals from said particular transceiver does not coincide.

30. The system as in claim 22 wherein said central processing unit includes a memory means for storing data pertaining to each room or area within said preselected group of rooms or areas and means for correlating and retrieving data from said memory means associated with said central processing unit to thereby provide a display of said data.

31. The system as in claim 15 wherein said central processing unit includes means for selectively providing status information to each location or area within said locations or areas in a set sequence.

32. In an AC power line communications system comprising a central processing unit and a plurality of transceivers each of which is located in a different room or area of a building or building complex and is assigned a unique address code, a method for transferring to said central processing unit information accumulated by a particular transceiver, said method comprising the steps of

periodically transmitting from said central processing unit an address signal which is representative of the address code assigned to said particular transceiver on the neutral and ground of the AC power line associated with said building or building complex,

transmitting from said particular transceiver a return signal on the neutral and ground of the AC power line associated with said building or building complex upon receipt of said address signal by said particular transceiver, and

receiving said return signal at said central processing unit.

33. The method as in claim 32 wherein said transmitting step of said transceiver comprises the steps of

receiving said address signal at said particular transceiver,

deriving an address code from the received address signal,

comparing the derived address code with the address code assigned to said particular transceiver, and

initiating transmission of said return signal if the derived address code coincides with the address code assigned to said particular transceiver.

34. In an AC power line communications system which is exposed to noise, said system comprising a plurality of transceivers each of which is located in a different room or area in a building or building complex, each of said transceivers being operable to accumulate data from various external sources and being assigned a unique address code, and a central processing unit having a memory means for storing the data accumulated by each of said transceivers, a method for updating the stored data pertaining to a particular transceiver, said method comprising the steps of

transmitting from said central processing unit an address signal which is representative of the address code assigned to said particular transceiver on the AC power line associated with said building or building complex;

transmitting from said particular transceiver a first return signal on the neutral and ground of the AC power line associated with said building or building complex upon receipt of said address signal by said particular transceiver, said return signal being representative of the data accumulated by said particular transceiver,

comparing in said central processing unit the data provided to said central processing unit by said first return signal with the stored data pertaining to said particular transceiver, and

transmitting from said central processing unit a succession of address signals which is representative of the address code assigned to said particular transceiver over the AC power line associated with said building or building complex if said comparing step yields a preselected difference.

35. The method as in claim 34 including the steps of

transmitting from said particular transceiver a second return signal on the neutral and ground of the AC power line associated with said building or building complex upon receipt of a second address signal by said particular transceiver, said second return signal being representative of the data accumulated by said particular transceiver,

comparing in said central processing unit the data provided to said central processing unit by said second return signal with the stored data pertaining to said particular transceiver,

comparing the data provided to said central processing by said first return signal with the data provided to said central processing unit by said second return signal if the data provided to said central processing unit by said second return signal does not coincide with the stored data pertaining to said particular transceiver, and

using the data provided to said central processing unit by one of the two return signals from said particular transceiver to update the stored data pertaining to said particular transceiver if the data provided to said central processing unit by said first return signal coincides with the data provided to said central processing unit by said second return signal.