AU780093B2 - Air conditioning zone controller - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

TO BE COMPLETED BY APPLICANT Name of Applicant: Nordin Engineered Air Technologies Pty Ltd Actual Inventor: Hong Du Address for Service: A.P.T. Patent and Trade Mark Attorneys PO Box 222, Mitcham, SA 5062 Invention Title: Air Conditioning Zone Controller Details of Associated Provisional Application No. PR4602 dated 26 April 2001 The following statement is a full description of this invention, including the best method of performing it known to me:- The present invention relates to a controller for controlling the flow of conditioned air into a room or zone and hence the air temperature in the room or zone.

BACKGROUND OF THE INVENTION Air conditioners are used widely to alter or regulate the air temperature of rooms in domestic dwellings, office complexes and retail complexes. Most office and retail complexes have ducted air conditioning and it is becoming more common for domestic dwellings to have ducted air conditioning systems installed. In these systems a central air conditioning unit is used to deliver conditioned air to a number of outlets in different rooms or areas. Typically ducts are used to transfer the conditioned air from the central unit to the respective outlets. It is also common for the air conditioning unit to be a reverse cycle unit which has the capacity to both cool and warm the air. Reverse cycle units are widely used in office buildings for this reason.

The temperature in any given room or area will be affected in part by the volume of conditioned air flowing from an outlet into the room. Thus, regulation of air flow is used in many systems to regulate the temperature of a room. In a so called Variable Air Velocity (VAV) air control system, the flow of air through a given duct or outlet is usually controlled by a damper having a valve that can be moved between a fully open position in which air flow through the damper is at a maximum, and a closed position in which air flow through the damper is at a minimum. Many air conditioning systems incorporate a thermostat which is located in a room and is used to control the output of the air conditioner according to a temperature that is set as desired by the user. In these systems an output from the thermostat is used to adjust a valve in a damper to thereby regulate the flow of air.

In most cases all dampers are controlled by one unit and therefore dampers that control flow into different areas will all be adjusted according to the output from a thermostat that may be in a different room. This type of system therefore does not allow for different air temperatures in different rooms or areas.

Control of damper output to a particular zone is generally achieved by a control arrangement that has required integration or at least connection to a central control facility. It has accordingly been awkward to install local control of damper output in response to local room temperature and especially as a retrofitted arrangement.

It is also common nowadays for an office space or a dwelling to be subdivided into zones and for thermostats to be located in each zone. In this way different air temperatures can be achieved in the different zones. Typically however there is more than one outlet in each zone and therefore using these systems it is still not possible to regulate the temperature in a single room for example. In addition, these systems require manual setting of the controller between heating and cooling settings. Thus when the thermostat detects a change in temperature a signal is usually sent back to a central control unit to decide whether the unit is in cooling or heating mode, and then the dampers are adjusted accordingly.

It will be appreciated that this distinction between heating and cooling modes is important because for example if the room needs to be cooled in winter then the damper will need to be closed because the unit will be in heating mode and therefore less hot air is needed in a room. The converse is true in the cooling mode for the room to be cooled further the damper needs to be opened to allow more cooled air to flow into a room.

OBJECT OF THE INVENTION An object of this invention is to provide an air conditioning zone controller that obviates or alleviates any one of the above problems, or at least to provide the public with a useful choice.

SUMMARY OF THE INVENTION In a first aspect, although not necessarily the broadest or only aspect, the invention could be said to reside in a locally operating control unit for controlling the air temperature in an air conditioned zone by regulating flow of conditioned air into that zone, the unit connected to a damper to control the flow of air through an outlet, the unit including temperature setting means for inputting a set point temperature, temperature sensing means for detecting the air temperature in the zone, storage means for storing detected air temperature values, processing means for comparing detected air temperature values collected over one or more time periods to determine whether the room temperature is rising or falling relative to the set point temperature and therefore whether the air conditioning unit is in heating or cooling mode, and control means for adjusting the damper to thereby adjust the volume of air flow from the outlet to increase the rate of convergence of air temperature to the set point temperature, a direction of adjustment being determined by whether the air conditioning unit is in the heating or cooling mode.

It will be appreciated that the control unit can be provided as a single, self contained unit and it may be connected with the damper of a single outlet, and as such there is no need to connect the control unit to the central air conditioning unit.

Therefore within any given area the air flow through individual outlets can be controlled. This allows for control of air temperature in individual offices within an office complex, or individual rooms within a domestic dwelling.

The storage means and processing means may be a microcontroller. Alternatively the temperature sensing means may contain memory for storing detected air temperature values and a microcontroller may be used to read the values and carry out the processing.

In most instances the damper will include a valve that can be rotated within the damper to control the flow of air therethrough. The valve may be a flap valve that has a similar cross section to an air passage within the damper and therefore can be used to block flow of air through the damper. The control means may include a motor to drive rotation of the valve. The control means may be an existing control means and therefore it is possible to fit the control unit into existing air conditioning systems.

Preferably, the temperature sensing means is in communication with the microcontroller and as such accepts commands from the microcontroller. The sensing means may include a temperature sensor and ROM so that a command can be sent to perform a temperature measurement and the result can be stored in memory and can be read from memory. The temperature sensing means preferably converts the temperature value to a digital word for processing by the microcontroller.

The microcontroller preferably controls inputs and outputs and in particular inputs from the temperature sensing means and temperature setting means. The microcontroller also preferably has memory.

The control means may be any suitable means for receiving signals from the microcontroller and driving rotation of the valve in response to the signal.

Preferably however it includes a stepper motor in connection with the valve in a damper. A driver may be used to drive the stepper motor. Typically, the stepper motor will require steps and direction signals from the driver. In one form the microcontroller may be used to genfierate the signal required to drive the stepper motor.

The temperature setting means preferably allows the user to set a desired temperature in 0.5 0 C steps. Preferably the temperature can be set within the range 20 to 25'C. The signal generated from the input could be either analog or digital although in the former case an ADC may be required for connection to the microcontroller. In one form, the temperature controller is a rotary switch having either 10 or 16 preset positions. A four bit binary code may be developed for each position.

To determine whether the system is in heating or cooling mode, the microcontroller may first read the room temperature measured by the temperature sensing means. If the room temperature is below 00 Celsius, the system may be acknowledged as being in heating mode. If the room temperature is above 400 Celsius, the system may be acknowledged as being in cooling mode. If the room temperature is between 0 and 400 Celsius, the microcontroller may fully open the valve and after a preset period the room temperature may be measured and read again. Then after a further preset period the temperature may be measured once more. The microcontroller may compare these values and if they are showing a rising trend then the system is acknowledged as being in heating mode, and if they are showing a dropping trend then the system is acknowledged as being in cooling mode. If the temperature values do not show the above patterns, the room temperature may be checked again and the above process repeated. This process may last for an hour with default being in cooling mode.

Optionally, the microcontroller may be programmed to periodically open the valve by a set amount at set intervals during periods when the valve is closed. In this way even during periods when there is little or no air flow into the room, some air is able to flow in order to avoid stagnation of the air. Preferably this process does not significantly alter the air temperature in the room.

The control unit may also include a timed function to set periods of time which the system can be shut off by closing the damper.

In a second aspect the invention could be said to reside in an air conditioning system including an air conditioning unit for heating and cooling air, distribution means for distributing conditioned air through one or more outlets, and the control unit of the first aspect of the invention.

In a third aspect, the invention could be said to reside in a method of controlling the air temperature in an air conditioned zone by regulating flow of conditioned air into the zone, the method including the steps of detecting the air temperature in the zone over one or more time periods to determine whether the room temperature is rising or falling and therefore whether the air conditioning unit is in heating or cooling mode, comparing the detected air temperature with a set point temperature, adjusting the volume of air flow into the zone so that the room temperature approaches the set point temperature.

Temperature sensing means may be used to detect the temperature in the zone.

Detected air temperature values may be stored in a storage means and processing means may be used to compare detected air temperature values collected to determine whether the room temperature is rising or falling.

The volume of air flow into the zone may be adjusted using control means for adjusting a damper to thereby adjust the volume of air flow from the outlet.

The set point temperature may be input as desired by a user using a temperature setting means.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding the invention will now be described with reference to an illustrated embodiment. The drawings describe an illustrated embodiment wherein, Figure 1 is a flow diagram of the control unit, Figure 2 shows a stepper motor drive circuit, Figure 3 is a flow diagram of the temperature control system, Figure 4 is a flow diagram of the timer function, Figure 5 is a flow diagram of the on/off function, Figure 6 is a flow diagram showing one set of steps in determination of heating or cooling process, Figure 7 shows plots of temperature vs time for heating and cooling processes, and Figure 8 is a flow diagram showing a second set of steps in determination of heating or cooling process.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Dimensions of certain of the parts shown in the drawings may have been modified and/or exaggerated for the purposes of clarity or illustration.

Figure 1 shows a flow diagram of the microcontroller based temperature control.

The control includes a microcontroller, a step motor, a step motor drive, a temperature sensor, a temperature setting switch, a microswitch and control algorithms.

The microcontroller controls input and output variables to achieve the required temperature control. One example of a suitable commercial microcontroller is manufactured by Motorola and is known as an MC68HC05JA, which has 1240 bytes of EPROM including eight bytes of user vectors, 64 bytes of user RAM, stage multifunction timer including 8-bit free running counter and four stage selectable real time interrupt generator, 14 bidirectional 1/O lines including sink capability on four O/0 pins, MOR (Mask Option Register) and software programmable pulldowns on all I/O pins and MOR selectable interrupt on four 1O pins.

The stepper motor may be any commercially available motor and for example 12 Volt and 24 Volt motors could be used with the unit of the illustrated embodiment.

Alternatively the motor could already be in place in an existing air conditioning system and the control unit of the present invention could be fitted to the motor.

The stepper motor needs sequential signal to be applied on its coils in order to move to the required position. A commercially available unipolar stepper motor could be used if necessary however it has been found that for the present application the temperature changes very slowly and therefore the control system does not require a fast response and the microcontroller itself has enough computing power and speed to generate the signal required for the stepper motor.

The transistor circuit of Figure 2 is used to drive the stepper motor.

The datum position of the stepper motor is achieved by using a microswitch interfaced to the microcontroller.

The temperature sensing means has three main data components: 64-bit lasered ROM; a temperature sensor; and nonvolatile temperature alarm triggers.

Temperature measurement is achieved using a commercially available Dallas temperature sensor, DS 1820 (Dallas Semiconductor Corporation). The temperature sensor measures temperatures from -55'C to +125 0 C in 0.5 0

C

increments. The temperature value is read as a 9-bit digital value which is converted to a digital word.

The temperature sensor is interfaced with the microcontroller using standard techniques. For example, a I-Wire port can be used to interface the microcontroller with the temperature sensor.

A control function command instructs the temperature sensor to perform a temperature measurement. The result of the measurement is placed in the sensors scratch pad memory and may be read by issuing a memory function command which reads the contents of the scratchpad memory. All data is read and written least significant bit (LSB) first.

Temperature is represented in the sensor means in terms of a 0.5°C LSB, yielding the following 9-bit format: MSB LSB 1 1 1 0 00 1 1 1 0 The most significant (sign) bit (MSB) is duplicated into all of the bits in the upper MSB of the two-byte temperature register in memory. This "sign extension" yields the 16-bit temperature readings as shown in Table 1.

Table 1 Temperature Digital Output (Binary) Digital Output (Hex) +125°C 00000000 11111010 OOFA 0 C 00000000 00110010 0032h 0 C 00000000 00000001 0001 h 0 0 C 00000000 00000000 0000h 0 C 11111111 1111111 FFFFh 0 C 11111111 11001110 FFCEh 11111111 10010010 FF92h Higher resolutions may be obtained by the following procedure. First, the temperature is read and the 0.5'C bit (the LSB) is truncated from the read value.

This value is Tr. The value left in the counter is then read. This value is the count remaining (CR) after the gate period has ceased. The last value needed is the number of counts per degree C (CPC) at that temperature. The actual temperature may then be calculated as follows: (CPC CR) T Tr 0.25

(CPC)

The microcontroller initiates temperature conversion, then reads temperature.

The temperature setting means is used to set the required temperature by a user.

This can be achieved analogly or digitally. A rotary switch having 10 or 16 positions can be used. In one embodiment a decimal rotary switch which generates a four-bit binary code for each position is interfaced with the microcontroller.

Figure 3 shows a flow diagram of the temperature control system. The temperature control system module begins with the installation of the control variables and definitions of variables in the system. It then proceeds to the detection of the datum position of the stepper motor. This is achieved by detecting whether the microswitch is closed or not. If not, the microcontroller keeps sending signals to the drive circuit until it detects the close signal of the microswitch. If it is closed, the datum of the stepper motor is obtained. The temperature control system then moves to its default setup, which is the system close mode. The system will then stay in this mode until a momentary switch for turning on/off the temperature control is pressed. If it is pressed, the system will proceed to the module of determination of the heating/cooling process of the temperature control.

Once the heating/cooling process is determined, the system reads the room temperature, checks the set room temperate and calculates the required positions for the air damper which is driven by the stepper motor. The system then executes the position control of the stepper motor by sending sequential signals to the drive circuit. Once the required position is obtained, the system delays for 15 seconds before it returns to the next system control cycle.

A timed function set module may also be incorporated into the system. This can be used to set the periods of time which the system will be shut off. The timed function can be implemented using external interrupt whereby an interrupt signal can be generated using a momentary switch. When the switch is turned off, the voltage related to ground is 5 volt. When it is turned on, the voltage is 0 volt.

The number of hours can be set by pushing the momentary switch once for each hour. Once the time is set, the system will be started 30 minutes earlier than the set time because the temperature control has a delay. Reset of the timed function can be achieved by pushing the switch until there is no buzz sound. A flow diagram of the timed function is shown in Figure 4.

The system switch on/off function for temperature control is implemented using external interrupts. The interrupt signal can be generated using a momentary switch. A flow diagram of the system on/off function is shown in Figure One of two algorithms can be used to determine the air conditioner heating or cooling mode. One algorithm can be based on whether the temperature is rising or dropping when the air damper is fully opened. The set room temperature is also considered to determine whether it is a heating or cooling process. A flow diagram of this algorithm is shown in Figure 6.

A second algorithm can be based on whether the room temperature is rising or dropping when the air damper is fully opened. The set room temperature is not considered. The sampling rate is set at 5 minutes. If the temperature is rising, as shown in Figure 7, it is a heating process. If the room temperature is dropping, as shown in Figure 7, it is a cooling process. Any other cases will be returned to the point where the room temperature is checked again and repeat the process. A flow diagram of the algorithm is shown in Figure 8.

The control unit may be available separately and retro-fitted into an existing air conditioning system, or alternatively it could be part of an air conditioning system.

Various features of the invention have been particularly shown and described in connection with the exemplified embodiments of the invention, however, it must be understood that these particular arrangements merely illustrate and that the invention is not limited thereto and can include various modifications falling within the spirit and scope of the invention.

Claims (30)

1. A control unit for controlling the air temperature in an air conditioned zone by regulating flow of conditioned air into that zone, the unit connected to a damper to control the flow of air through an outlet, the unit including temperature setting means for inputting a set point temperature, temperature sensing means for detecting the air temperature in the zone, storage means for storing detected air temperature values, processing means for comparing detected air temperature values collected over one or more time periods to determine whether the room temperature is rising or falling and therefore whether the air conditioning unit is in heating or cooling mode, and control means for adjusting the damper to thereby adjust the volume of air flow from the outlet to increase the rate of convergence of air temperature to the set point temperature, a direction of adjustment being determined by whether the air conditioning unit is in the heating or cooling mode.

2. The control unit as in claim 1 wherein the control unit is operational locally relative to the zone being unconnected to a central air conditioning unit.

3. The control unit as in claim 2 wherein the control unit operates one damper only.

4. The control unit as in any one of the preceding claims wherein the storage means and processing means is a microcontroller. The control unit as in any one of the preceding claims wherein air temperature values are collected over one or more fixed time periods

6. The control unit as in any one of the preceding claims wherein the temperature sensing means is connected with a memory for storing detected air temperature values and a microcontroller is used to read the values and carry out the processing.

7. The control unit as in any one of the preceding claims wherein the temperature sensing means is in communication with the microcontroller to accepts commands from the microcontroller and the sensing means include a temperature sensor and ROM so that a command can be sent to perform a temperature measurement and the result can be stored in memory and can be read from the memory.

8. The control unit as in any one of the preceding claims wherein the temperature sensing means converts the temperature value to a digital word for processing by the microcontroller.

9. The control unit as in any one of the preceding claims wherein the microcontroller controls inputs from the temperature sensing means and temperature setting means. The control unit as in any one of the preceding claims wherein the temperature setting means allows the user to set a desired temperature in 0.5 0 C steps. S11. The control unit as in any one of the preceding claims wherein the temperature can be set within the range 20 to 25 0 C.

12. The control unit as in any one of the preceding claims wherein the temperature controller is a rotary switch having either 10 or 16 preset positions.

13. The control unit as in any one of the preceding claims wherein the steps to determine whether the system is in heating or cooling mode, include the microcontroller first reading the room temperature measured by the temperature sensing means, if the room temperature is below 00 Celsius, the system may be acknowledged as being in heating mode, if the room temperature is above 400 Celsius, the system may be acknowledged as being in cooling mode, if the room temperature is between 0 and 400 Celsius, the microcontroller may fully open the valve and after a preset period the room temperature may be measured and read again, then after a further preset period the temperature may be measured once more, the microcontroller may compare these values and if they are showing a rising trend then the system is acknowledged as being in heating mode, and if they are showing a dropping trend then the system is acknowledged as being in cooling mode, if the temperature values do not show the above patterns, the room temperature may be checked again and the above process repeated.

14. The control unit as in any one of the preceding claims wherein the microcontroller may be programmed to periodically open the damper by a set amount at set intervals during periods when the valve is closed. The control unit as in any one of the preceding claims wherein the control unit includes a timed function to set periods of time which the system can be shut off by closing the damper.

16. The control unit as in any one of the preceding claims wherein the damper includes a valve that can be rotated within the damper to control the flow of air therethrough, the valve has a similar cross section to an air passage within the damper and can closed to block flow of air through the damper, the control means including a motor to drive rotation of the valve.

17. The control unit as in claim 16 wherein the control means receives signals from the microcontroller and drives rotation of the valve in response to the signal.

18. The control unit as in either claim 16 or 17 wherein the control means includes a stepper motor in connection with the valve in the damper.

19. The control unit as in any one of claims 16 to 18 wherein a driver is used to drive the stepper motor the stepper motor receiving steps and direction signals from the driver. The control unit as in any one of claims 16 to 19 wherein the microcontroller generates the signal required to drive the stepper motor.

21. A method of controlling the air temperature in an air conditioned zone by regulating flow of conditioned air into the zone, the method including the steps of detecting the air temperature in the zone over one or more time periods to determine whether the room temperature is rising or falling and therefore whether the air conditioning unit is in a heating mode or a cooling mode, comparing the detected air temperature with a set point temperature, adjusting the volume of air flow into the zone so that the room temperature approaches the set point temperature, a direction of adjustment being determined by whether the air conditioning unit is in the heating of cooling mode.

22. A method of controlling the air temperature as in claim 21 wherein temperature sensing means is used to detect the temperature in the zone.

23. A method of controlling the air temperature as in claim 22 wherein detected air temperature values are stored in a storage means and a processing means is used to compare detected air temperature values collected to determine whether the room temperature is rising or falling.

24. A method of controlling the air temperature as in any one of claims 21 to 23 wherein the volume of air flow into the zone is adjusted by adjusting a damper to thereby adjust the volume of air flow from the outlet. A method of controlling the air temperature as in any one of claims 21 to 24 wherein the set point temperature is input by a user using a temperature setting means.

26. A method of controlling the air temperature as in claim 25 wherein the temperature setting means allows the user to set a desired temperature in 0.5 0 C steps.

27. A method of controlling the air temperature as in either claim 21 or 33 wherein the temperature can be set within the range 20 to

28. A method of controlling the air temperature as in any one of claims 21 to 27 wherein air temperature values are collected over one or more fixed time periods

29. A method of controlling the air temperature as in claim 23 wherein the storage means and processing means is a microcontroller.

30. A method of controlling the air temperature as in claim 29 wherein the temperature sensing means is in communication with the microcontroller to accepts commands from the microcontroller and the sensing means include a temperature sensor and ROM so that a command can be sent to perform a temperature measurement and the result can be stored in memory and can be read from the memory.

31. A method of controlling the air temperature as in either claims 29 or wherein the temperature sensing means converts the temperature value to a digital word for processing by the microcontroller.

32. A method of controlling the air temperature as in any one of claims 29 to 31 wherein the microcontroller controls inputs from the temperature sensing means and temperature setting means.

33. A method of controlling the air temperature as in any one of claims 29 to 32 wherein the steps to determine whether the system is in heating or cooling mode, include the microcontroller first reading the room temperature measured by the temperature sensing means, if the room temperature is below 0' Celsius, the system may be acknowledged as being in heating mode, if the room temperature is above 400 Celsius, the system may be acknowledged as being in cooling mode, if the room temperature is between 0 and 40' Celsius, the microcontroller may fully open the valve and after a preset period the room temperature may be measured and read again, then after a further preset period the temperature may be measured once more, the microcontroller may compare these values and if they are showing a rising trend then the system is acknowledged as being in heating mode, and if they are showing a dropping trend then the system is acknowledged as being in cooling mode, if the temperature values do not show the above patterns, the room temperature may be checked again and the above process repeated.

34. A method of controlling the air temperature as in any one of claims 29 to 32 wherein the microcontroller may be programmed to periodically open the valve by a set amount at set intervals during periods when the valve is closed. A method of controlling the air temperature as in any one of claims 21 to 34 wherein the method includes a timed function to set periods of time which the system can be shut off by closing the damper. 17

36. A method of controlling the air temperature substantially hereinbefore described with reference to the description.

47. A control unit for controlling the air temperature in an air conditioned zone substantially hereinbefore described with reference to the description. Dated this 19th day of April 2002 NORDIN ENGINEERED AIR TECHNOLOGIES PTY LTD By their Patent Attorneys A.P.T. Patent and Trade Mark Attorneys