Electronic thermostat

• US 4,314,665 A
• Filed: 01/28/1980
• Issued: 02/09/1982
• Est. Priority Date: 03/17/1977
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Michael R. Levine
• Inventors: Levine, Michael R.
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US06/116,064
• Time in Patent Office: 743 Days
• Field of Search: 236/46 R, 236/47, 340/309.1, 165/12, 364/500, 219/492, 62/157
• US Class Current: 236/46.00R
• CPC Class Codes: G05D 23/1904 variable in time
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor

Abstract

A thermostat for generating control signals for a furnace, air conditioner, or the like, employs a constant frequency periodically alternating electrical source and an oscillator incorporating an element having a thermal-sensitive electrical characteristic so the oscillator frequency varies as a function of the ambient temperature. A comparator receives the two outputs and generates a signal representative of the ambient temperature. The stable output is also provided to dividing circuits to generate a signal representative of the time that is used to interrogate a digital memory storing a desired temperature-time program for the thermostat for a repetitive period, such as a week or month. The ambient temperature signal is compared with the desired temperature signal to generate an output conrol signal. A display provides a read-out of time and temperature and is used along with keyboard or the like in programming the memory.

Claims

1. A thermostat for controlling the application of electrical power to a temperature modifying load, comprising:

means for generating an electrical signal having a characteristic which varies as a function of the ambient temperature on the thermostat;

a clock operative to generate digital electrical signals having values representative of real time over a repetitive cycle;

a programmable, digital memory;

means for loading said memory with a program of digital signals representative of desired temperatures for different times over said repetitive time cycle, circuitry for applying the output of the clock to the memory to generate a digital electric signal representative of the desired temperature at the instant time;

means for receiving the electrical signal having a characteristic which is a function of ambient temperature and the output of the memory and for generating a control signal for said temperature modifying devices as a function of their differences.

2. The thermostat of claim 1 including a display device and means for connecting the display device to said electrical signal having a characteristic which varies as a function of ambient temperature and to the output of the clock.

3. The thermostat of claim 1 including manually operable means for programming said memory.

4. The thermostat of claim 1 wherein said clock comprises a digital divider chain driven by a periodically varying electrical signal having a frequency independent of the ambient temperature of the device.

5. The thermostat of claim 4 wherein said electrical signal having a characteristic which varies as a function of the ambient temperature on the thermostat comprises an oscillator having a temperature dependent element in its tank circuit.

6. The thermostat of claim 4 wherein said means for generating an electrical signal having a characteristic which varies as a function of the ambient temperature on the thermostat includes means for receiving said periodically varying signal and said electrical signal having a characteristic which varies as a function of the ambient temperature on the thermostat.

7. The thermostat of claim 1 wherein the electrical signal having a characteristic which varies as a function of the ambient temperature in the thermostat is digital.

8. A thermostat of claim 7 wherein the thermostat is formed as an integrated semi-conductor circuit.

9. The thermostat of claim 1 including a source of a constant frequency, periodically alternating electrical signal forming part of both said means for generating an electrical signal having a characteristic which varies as a function of the ambient temperature on the thermostat and said clock.

10. A thermostat for generating control signals for a temperature modifying device, comprising:

means for generating a digital electrical signal representative of the ambient temperature on the thermostat;

means for generating a digital electrical signal representative of the time within a repetitive time cycle;

a programmable digital memory;

means for loading said memory with a program of digital signals representative of desired temperatures for different times over said repetitive time cycle;

circuit means for interrogating said memory with said digital time signal to generate a digital signal representative of the desired temperature at the existing time; and

a comparator operative to receive the digital signal representative of the ambient temperature on the thermostat and the digital signal representative of the desired temperature, and to provide a control signal to said temperature modifying device.

11. The thermostat of claim 10 wherein said means for generating a digital electrical signal representative of the time within a repetitive time cycle includes means for generating a constant frequency periodically varying electrical signal, and said means for generating a digital electrical signal representative of the ambient temperature on the thermostat includes a temperature sensitive oscillator and means for receiving the output of the oscillator and the constant frequency signal.

12. The thermostat of claim 10 wherein said means for generating a digital time signal comprises an oscillator which has a constant frequency output at ambient temperatures over the range of the thermostat and a divider chain operative to receive the output of the oscillator.

13. The thermostat of claim 10 wherein said means for loading said memory with a program of desired temperatures for different times over a repetitive time cycle includes a manually operable keyboard.

14. The thermostat of claim 10 including digital means for modifying the output of the memory to generate a signal which is provided to the comparator in order to offset the temperature occurrence of the control signal with respect to the ambient temperature.