Low battery detector for a wireless sensor

• US 5,942,981 A
• Filed: 02/09/1996
• Issued: 08/24/1999
• Est. Priority Date: 02/09/1996
• Status: Expired due to Term

• Current Assignee: GE Security Incorporated (Carrier Global Corporation)
• Original Assignee: Interactive Technologies, Inc. (Fiserv Incorporated)
• Inventors: Kackman, Gerald M.
• Primary Examiner(s): Hofsass, Jeffery A.
• Assistant Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US08/599,087
• Time in Patent Office: 1,292 Days
• Field of Search: 340/636, 371/37.1, 370/338, 370/445, 320/48
• US Class Current: 340/636.15
• CPC Class Codes: G08B 29/181 due to failing power supply

Abstract

Measuring the critical value of a parameter of a sensor in a security system (e.g., battery voltage) is performed at a time when the critical value is most likely to be reached, and the critical value information is sent from the sensor to a system controller at a time when the information is most likely to be successfully received.

Claims

1. A method for monitoring a parameter in a device for sending messages, the method comprising:

a) measuring a value of the parameter existing at a time during the sending of a first message by the sending device;

b) sending a second message from the sending device reporting the value of the parameter over a communication channel to a system controller, the second message being sent at a time subsequent to the sending of the first message.

2. The method of claim 1 wherein the parameter comprises an energy level.

3. The method of claim 2 wherein the energy level decreases during the sending of the first message.

4. The method of claim 1 wherein a critical value of the parameter is more likely to be reached near the end of the first message, and the measuring step includes measuring a value of the parameter at a time near the end of the sending of the first message.

5. The method of claim 4 wherein the parameter comprises an energy level, and the critical value comprises an energy level at which communication of the first message by the message sending device may not be successful.

6. The method of claim 5 wherein the first message is more likely to be successfully communicated by the message sending device when the energy level is higher than the critical value.

7. The method of claim 1 wherein the measuring comprises using a sensing device that is battery powered, and the parameter comprises the battery level, wherein a critical value of the battery level is more likely to be reached near the end of the first message.

8. The method of claim 7, wherein each of the messages comprises a group of message packets, the battery level is measured during the last packet of the first message, and the battery level is reported in the first packet of a next succeeding group of packets in the second message.

9. The method of claim 7 wherein the critical value is about 2.6 volts.

10. A method of detecting a low-power level of a sensor which sends groups of message packets, comprising:

a) measuring a power level of the sensor existing at a time during sending of a first group of message packets by the sensor; and

b) sending from the sensor the measured power level as part of a second group of message packets, the second group of message packets being sent at a time subsequent to the sending of the first group of message packets.

11. The method of claim 10 wherein the measuring is done near the end of sending the first group of message packets.

12. The method of claim 10 further comprising comparing the measured power level with a predetermined reference value.

13. The method of claim 12 further comprising battery-powering the sensor and wherein the reference value is about 2.6 volts.

14. The method of claim 10 wherein the sending includes sending the power level in the first packet of a next succeeding group.

15. The method of claim 14 wherein the sending step includes sending the power level as part of each message packet of a next succeeding group.

21. The method of claim 11, wherein the measuring is done near the end of the last packet of the first group.

16. A low-battery detector for a battery-powered sensor which sends messages containing message packets to a system controller, comprising:

a) a reference voltage;

b) a comparator connected to the reference voltage and a battery of the sensor, and adapted to generate an output signal indicative of the battery level; and

c) a transmitter, operably connected to the comparator, for including in a group of message packets the output signal generated by the comparator, the output signal being indicative of the battery level existing a time during sending of an earlier group of message packets, wherein the group of message packets including the output signal is sent subsequent to the sending of the earlier group of message packets.

17. The apparatus of claim 16, wherein the output signal indicates whether the battery level is above or below a reference voltage.

18. The apparatus of claim 17, wherein the output signal comprises a logical 1 when the battery level is below the reference voltage and a logical 0 when the battery level is above or equal to the reference voltage.

19. The apparatus of claim 16 further including a packet counter for counting the number of packets in a group and generating a signal when the last packet in a group is counted, and wherein the comparator is enabled by the last packet signal.

20. A sensor which sends messages containing message packets to a system controller, comprising:

a packet generator for generating the message packets,

a low battery detector operably connected to the packet generator, the detector comprising,

a) a reference voltage,

b) a comparator connected to the reference voltage and a battery of the sensor, and adapted to generate an output signal indicative of the battery level existing at a time during the generation of a first group of message packets, and

wherein the packet generator includes the comparator output signal in a second group of message packets in a succeeding message generated subsequent to the first group of message packets.

22. A low-battery detector for a battery-powered sensor which sends messages containing message packets to a system controller, comprising:

a) a reference voltage;

b) a comparator connected to the reference voltage and a battery of the sensor, and adapted to generate an output signal indicative of the battery level; and

c) a transmitter, operably connected to the comparator, for including in a next succeeding group of packets the output signal generated at a time during one of the messages, wherein the transmitter includes in the next succeeding group of packets the output signal generated at a time near the end of one of the messages.

23. A sensor which sends messages containing message packets to a system controller, comprising:

a packet generator for generating the message packets,

a low battery detector operably connected to the packet generator, the detector comprising;

a) a reference voltage, and

b) a comparator connected to the reference voltage and a battery of the sensor, and adapted to generate an output signal indicative of the battery level,

wherein the packet generator includes in a succeeding group of packets in a succeeding message the comparator output signal generated at a time near the end of one of the messages.

24. A battery-powered sensor module comprising:

a transmitter for transmitting messages containing information indicative of one or more sensor parameters;

a battery for powering the sensor module, wherein a power level of the battery generally varies from a lower power level near the end of transmission of one of the messages to a higher power level near the start of transmission of one of the messages; and

a battery level indicator for indicating a power level of the battery,

wherein the transmitter transmits with one of the messages battery information indicative of the power level of the battery existing at a time near the end of transmission of one of the messages, and transmits the battery information near the start of transmission of a subsequent one of the messages.

25. The sensor module of claim 24, wherein each of the messages includes a plurality of message packets, and the transmitter transmits with one of the messages battery information indicative of the power level of the battery existing at a time near the end of the last one of the message packets of one of the messages.

26. The sensor module of claim 25, wherein the transmitter transmits the battery information near the start of the first one of the message packets of a subsequent one of the messages.

27. A battery-powered sensor module comprising:

a transmitter for transmitting messages containing information indicative of one or more sensor parameters;

a battery for powering the sensor module; and

a battery level indicator for indicating a power level of the battery existing at a time during transmission of a first message,

wherein the transmitter transmits battery information indicative of the power level of the battery existing at the time during the transmission of the first message with a subsequent one of the messages.

28. A battery-powered sensor module comprising:

a transmitter for transmitting messages containing information indicative of one or more sensor parameters;

a battery for powering the sensor module; and

a battery level indicator for indicating a power level of the battery,

wherein the transmitter transmits battery information indicative of the power level of the battery existing at a time near the end of transmission of a previous one of the messages, wherein each of the messages includes a plurality of message packets, and the transmitter transmits with one of the messages battery information indicative of the power level of the battery existing at a time near the end of the last one of the message packets of one of the messages.

29. A method for monitoring a power level of a battery in a battery-powered sensor module, wherein the sensor module transmits messages containing information indicative of one or more sensor parameters, wherein a power level of the battery generally varies from a lower power level near the end of transmission of one of the messages to a higher power level near the start of transmission of one of the messages, the method comprising the steps of:

indicating the power level of the battery; and

transmitting to a system controller with one of the messages battery information indicative of the power level of the battery existing at a time during transmission of a previous one of the messages.

30. A battery-powered sensor module comprising:

a sensor circuit for generating information indicative of one or more sensed conditions;

a battery for powering the sensor circuit;

a battery level indicator for indicating a power level of the battery;

a transmitter for transmitting messages containing the information generated by the sensor circuit, wherein the transmitter transmits battery information indicative of the power level of the battery existing at a time during transmission of one of the messages, the battery information being transmitted with a subsequent one of the messages.