GB2573575A

GB2573575A - A temperature controller

Info

Publication number: GB2573575A
Application number: GB1807703.2A
Authority: GB
Inventors: Crompton Phil; Clarke Barry; Johnson Richard
Original assignee: Genlab Ltd
Current assignee: Genlab Ltd
Priority date: 2018-05-11
Filing date: 2018-05-11
Publication date: 2019-11-13
Also published as: GB201807703D0

Abstract

A controller 5 for a temperature-controlled apparatus includes a control switch 21, such as a triac, and an overheat switch 26, such as a contactor or relay, for connection in series with a power supply 6 and a heating element 14. The controller has a microcontroller 18 connected to the control switch to toggle the control switch between conducting and non-conducting states. The microcontroller is configured to implement a watchdog function 32, which is configured to detect an error state in the microcontroller. The watchdog is configured to control a watchdog output 34 of the microcontroller. The watchdog output is connected to the overheat switch to toggle the overheat switch into a non-conducting state upon detection by the watchdog of the error state in the microcontroller. An extension module for a controller for a temperature-controlled apparatus is also provided to enable operation with a three-phase power supply.

Description

A TEMPERATURE CONTROLLER

Field of the Invention

The present invention relates to temperature controlled-environments and particularly, although not exclusively, to controllers for temperature-controlled apparatus in which a temperature-controlled environment is maintained.

Background

Temperature-controlled environments include apparatuses having a chamber that can be substantially maintained at a chosen temperature. Examples include industrial ovens, kilns, incubators, driers and sterilizers.

Industrial ovens are of particular importance, having uses in many industries. For example:

• For the curing of plastic components • PCB (printed circuit board) production re-flow processes • Heat treatment of high performance parts, for example in the aerospace industry • Materials testing, in which a sample is subjected to controlled temperature conditions;

• Curing of composite materials • Drying processes, for example the drying of glassware;

• Conveyor and tunnel ovens for use with a continuous manufacturing process.

A temperature controlled environment, which will be hereby be referred to using the example of an industrial oven, requires accurate and safe temperature control. In other words, the temperature inside the oven should closely correspond to the temperature requested by a user. If the temperature inside the oven does not correspond to the temperature requested by the user, then the oven and its controller should safely address that issue.

For example, if the temperature inside the chamber does not substantially correspond to the temperature requested by the user, i.e. if the oven overheat or underheats then the task being carried out by the oven may be unsuccessful. For example, when the industrial oven is being used to cure a component, if the temperature in the chamber does not follow accurately the temperature requested by the user, then components being cured may be damaged, or may not perform to the expected standards.

A known method of controlling the temperature in a temperature controlled chamber is to provide two temperature sensors located in the temperature controlled environment: a primary temperature sensor and a secondary temperature sensor.

The primary temperature sensor is used to control a heating element in the chamber. When the heating element is energized to heat up - the temperature rises. When the temperature exceeds a target value as measured by the primary sensor, the heating element is deactivated. The temperature inside the chamber consequently decreases. When the temperature then falls again below the target value as measured by the primary sensor, then the heating element is reactivated. The temperature inside the chamber consequently increases. Under normal operating conditions, the primary sensor and heating element together operate such that the heating element is powered on and off to maintain the temperature inside the chamber substantially at the target temperature.

The secondary temperature sensor is also measuring the temperature in the chamber. A comparator compares a signal corresponding to the temperature measurement from the second temperature sensor to a signal corresponding to a fixed maximum temperature. The comparator produces a high-temperature output signal when the temperature measurement from the second temperature measurement exceeds the fixed maximum temperature. The output of the comparator is wired to a gate of a contactor. The contactor is in series with the power supply, so when a signal from the comparator causes the contactor to move into a disconnected state, the power supply is disconnected from the heater. The temperature consequently falls and the risk is mitigated. The secondary sensor provides a crude emergency cut-off in the event of an overheat condition.

For example, high performance tasks requiring a temperature-controlled apparatus can require accurate temperature control over long periods. Overheating must therefore be carefully monitored. For many industrial applications, even small temperature fluctuations inside the chamber can lead to objects inside being damaged. Furthermore, for an overheating condition, the temperature could potentially rise to such an extent that the industrial oven becomes a safety risk, for example a fire risk.

There is a need for accurate and safe temperature control of a temperature-controlled apparatus. The present invention has been devised in light of the above considerations.

Summary of the Invention

According to a first aspect, a controller for a temperature-controlled apparatus is provided, the apparatus including a heating element for connection to a power supply, wherein the controller includes: a control switch for connection in series with the power supply and the heating element; an overheat switch for connection in series with the power supply and the heating element; a microcontroller connected to the control switch to thereby toggle the control switch between conducting and non-conducting states; wherein the microcontroller is configured to implement a watchdog configured to detect an error state in the microcontroller; and wherein the watchdog is configured to control a watchdog output of the microcontroller, wherein the watchdog output is connected to the overheat switch to toggle the overheat switch into a non-conducting state upon detection by the watchdog of the error state in the microcontroller.

Optionally, the control switch is configured to disconnect the power supply from the heating element when the control switch is in the non-conducting state.

Optionally, the overheat switch is configured to disconnect the power supply from the heating element when the overheat switch is in the non-conducting state.

Optionally, the controller further including a watchdog connection between the overheat switch and the microcontroller, wherein the watchdog is configured to toggle the overheat switch into the non-conducting state by application of an overheat signal on the watchdog connection.

Optionally, wherein the microcontroller is configured for connection to a control temperature sensor and to an overheat temperature sensor.

Optionally, the control temperature sensor is configured to provide a signal representative of a control temperature measurement of the temperature-controlled environment to the microcontroller.

Optionally, the overheat temperature sensor is configured to provide a signal representative of an overheat temperature measurement of the temperature-controlled environment to the microcontroller.

Optionally, the microcontroller is configured to toggle the overheat switch into a non-conducting state when an overheat condition is detected by the microcontroller.

Optionally, the overheat condition is determined based on a difference between the overheat temperature measurement and a target temperature.

Optionally, the microcontroller is configured implement a temperature control protocol.

Optionally, the temperature control protocol includes toggling the control switch based on the control temperature measurement.

Optionally, the control switch includes a TRIode for Alternating Current (“TRIAC”)

Optionally, the control switch is in thermal contact with a housing of the controller.

Optionally, the overheat switch includes one of: a contactor or an electro-mechanical relay.

Optionally, the controller further includes a supplementary switch, and wherein the microcontroller is connected to the supplementary switch to toggle the supplementary switch between conducting and nonconducting states.

Optionally, the temperature controlled apparatus is an industrial oven.

Optionally, the supplementary switch is configured for connection to a fan in the industrial oven.

Optionally, a temperature controlled apparatus is provided, including a controller according to the first aspect.

According to a second aspect an extension module for connection to a controller for a temperaturecontrolled apparatus is provided, the apparatus including a first heating element for connection to a power supply, wherein the extension module includes: a first control switch for connection in series with the power supply and the first heating element; a first overheat switch for connection in series with the power supply and the first heating element; a first control input to the extension module, the first control input connected to the first control switch, the first control input configured to receive a first control signal to toggle the first control switch between conducting and non-conducting states; and a watchdog input to the extension module, the watchdog input connected to the first overheat switch, the watchdog input configured to receive a watchdog signal to toggle the first overheat switch between conducting and nonconducting states.

Optionally, the first control switch and first overheat switch are for connection in series with a first phase of the power supply.

Optionally, the extension module further including a second control switch and a second overheat switch for connection in series with a second phase of the power supply.

Optionally, the extension module further including a second control input connected to the second control switch, the second control input configured to receive a second control signal to toggle the second control switch between conducting and non-conducting states; wherein the watchdog input is connected to the second overheat switch to toggle the second overheat switch between conducting and non-conducting states.

Optionally, the first control switch is in thermal contact with a housing of the extension module.

Optionally, wherein the second control switch is in thermal contact with a housing of the extension module.

Optionally, wherein the first overheat switch is a contactor, an electro-mechanical relay.

Optionally, wherein the second overheat switch is a contactor, an electro-mechanical relay.

Optionally, the first control switch is a TRIAC.

Optionally, wherein the second control switch is a TRIAC.

According to a third aspect, a controller for a temperature-controlled apparatus is provided, the controller configured to control the temperature in a chamber of the temperature controlled apparatus, the controller including a microcontroller, wherein: the microcontroller is configured to control the temperature in the chamber according to at least three control protocols in which: a timer protocol implements a timer function, wherein the temperature in the chamber is maintained at a first set value for a first set period; a real-time clock protocol implements a real time function, wherein the real time function can put the apparatus into a standby state between an off time and an on time; a profile protocol includes a profile function, wherein the temperature in the chamber is controlled to substantially follow a temperature profile.

Optionally, the temperature profile is a user-defined target temperature in the chamber as a function of time.

Optionally, the temperature profile includes a plurality of temporal stages.

Optionally, each stage is one of: a constant temperature stage; a rising temperature stage; or a falling temperature stage.

Optionally, each stage includes a stage duration, a stage temperature, and a stage ramp.

Optionally, the controller is configured to toggle the connection of a heating element to a heating supply to thereby control the temperature in the chamber.

Optionally, the controller is configured for connection a temperature sensor located in the chamber.

Optionally, the controller is configured to control the toggle the connection of a heating element to a heating supply using a proportional-integral-derivative (“PID”) controller.

Optionally, feedback to the PID controller includes a temperature measurement from the temperature sensor.

Optionally, the controller is configured to implement a band alarm function, wherein if the temperature measurement falls outside a band centred on an instantaneous target temperature, a band alarm procedure is activated.

Optionally, the controller is configured to implement a high temperature alarm function, wherein if the temperature measurement exceeds a maximum temperature, a high temperature alarm procedure is activated.

The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

Summary of the Figures

Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

Figure 1 is an illustration of an apparatus including a controller in accordance with the present invention;

Figure 2 is a schematic representation of the apparatus of Figure 1;

Figure 3.is a schematic representation of the controller of Figures 1 and 2 in combination with a heating element;

Figure 4 is a schematic representation of the controller of Figures 1-3, in combination with an extension module in accordance with the present invention.

Figure 5 is a schematic representation of the extension module of Figure 4.

Figure 6 a schematic representation of another controller in accordance with the present invention;

Figure 7 a schematic representation of the controller of Figure 6, and;

Figure 8 an illustration of an operating protocol of the controller of Figures 6 and 7.

Detailed Description of the Invention

Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

Figure 1 illustrates a temperature-controlled apparatus 1 in accordance with the present invention. The temperature-controlled apparatus includes an industrial oven 2. The industrial oven 2 will hereby be referred to as the oven 2 for convenience. Inside the oven 2 is a temperature-controlled chamber, into which the user can place objects I components I parts I samples to be exposed to the temperaturecontrolled environment of the chamber. The chamber is accessible via the door 3 using handle 4.

The oven 2 has a controller 5 according to the present invention. The controller 5 is shown mounted on the side of the oven 2, however it will be appreciated that the controller 5 could be located elsewhere on the oven 2. The controller may equally be integrated in to a housing of the oven 2.

The controller 5 includes user controls 6 which allow a user of the oven 2 to control at least some aspects of the operation of the oven 2 and controllers. The user controls 6 may include a display, buttons, knobs and other conventional input means. If a display is provided, the display may be a touchscreen display.

The controller 5 may also allow user interaction via an input data connection port to the controller 5. The user may connect a compute device to the data connection port, which he/she can use to interact with the controller 5. For example, the controller 5 may include a Universal Serial Bus (“USB”) port as a data connection port.

In general, the controller 5 controls the operation of the oven 2. In particular, the controller 5 controls the temperature inside the chamber of the oven 2.

The oven 2 is connected to power supply 6. The power supply 6 may be a conventional mains power supply (i.e. 240 V 50 Hz AC, in the UK). The power supply 6 may alternatively be a so-called “threephase power supply. For example, the power supply 6 may include three phases of AC current, each offset by 120 degrees of phase from one another. Each phase may be a 240 V supply. Other electrical power supply systems are also envisaged for the power supply 6, e.g. mains supplies and multiphase power supplies available inside or outside the UK.

Figure 1 illustrates the power supply 6 as being connected to the oven 2. However, the power supply 6 may equally connect substantially to the controller 5.

Figure 2 illustrates the apparatus 1 of Figure 1 schematically. The oven 2 includes a heating chamber 8. A control temperature sensor 9 and an overheat temperature sensor 10 are located inside the heating chamber 8. The temperature sensor 9 and the overheat temperature sensor 10 may be a duplex isolated temperature probe.

The control temperature sensor 9 produces a temperature control signal that that is representative of the temperature inside the chamber 8. The temperature control signal may be analogue (e.g. a resistance measurement, which may be proportional to the temperature inside the chamber). The controller 5 is thereby configured to determine the temperature of the chamber 8, as measured by the control temperature sensor 9. The controller 5 may be configured to present the temperature inside the chamber to the user on the display. The controller 5 may be substantially permanently connected to the control temperature sensor 9, or the controller 5 may include an input port for connection to the control temperature sensor 9. In any case, the control temperature sensor 9 is connected to the controller 5 via a control sensor connection 11.

The overheat temperature sensor 10 produces a temperature overheat signal that that is representative of the temperature inside the chamber 8. The temperature overheat signal may be analogue (e.g. a current or voltage that is proportional to the temperature inside the chamber 8), or alternatively may be digitally represented. The controller 5 is thereby configured to determine the temperature of the chamber 8, as measured by the overheat temperature sensor 10. The controller 5 may be substantially permanently connected to the overheat temperature sensor 10, or the controller 5 may include an input port for connection to the overheat temperature sensor 10. In any case, the overheat temperature sensor 10 is connected to the controller 5 via an overheat sensor connection 12.

A heating element 14 is located inside the heating chamber 8. The heating element 14 is connected to the controller 5 via a heater connection 15. The heater connection 15 includes a heater power supply connection that connects the heating element 14 to a power supply 6. When the power supply 6 is connected to the heating element 14, the heating element heats up. In effect, the controller 5 is located between the power supply 6 and the heating element 14. The controller 5 is configured to allow electrical current to flow through the heating element 14, or to prevent electrical current flowing through the heating element 14. The controller 5 is thus configured to connect and disconnect the power supply 6 from the heating element 14. Thus, the controller 5 is configured to toggle the heating element 14 between an energized, connected, hot state, and a de-energized, disconnected, cooler state. It will be appreciated that via the control of such toggling of the heating element 14, the temperature in the chamber 8 can be controlled. The heater connection 15 is illustrated as a single line in Figure 2. However, it will be appreciated that the controller 5, heater connection 15 and the heater 14 form a complete (but breakable) circuit. This is illustrated in Figure 3.

A fan 16 is located inside the heating chamber 8. The fan 16 is connected to the controller 5 via a fan connection 17. The fan connection 17 includes a fan power supply connection that connects the fan 16 to a fan power supply, which may be the power supply 6. When the fan power supply is connected to the fan 16, the fan 16 is powered on. The fan 16 may be used to circulate air within the heating chambers. In effect, the controllers is located between the fan power supply and the fan 16. In other words, the controller 5 is configured to allow electrical current to flow through the fan 16, or to prevent electrical current flowing through the fan 16. In other words, the controller 5 is configured to connect and disconnect the fan power supply from the fan 16. Thus, the controller 5 is configured to toggle the fan 16 between a circulating and non-circulating state. The fan connection 17 is illustrated as a single line in Figure 2. However, it will be appreciated that the controller 5, fan connection 17 and the fan 16 form a complete (but breakable) circuit.

Figure 3 illustrates the controller 5 of Figures 1 and 2 schematically. The controller 5 is shown connected, in series, with the power supply 6 and the heating element 14. The control sensor connection 11 and the overheat sensor connection 12 are shown as input connections to the controller 5.

The controllers includes a microcontroller 18. The microcontroller 18 has a plurality of input pins and a plurality of output pins. For example, the control temperature connection 11 may be connected to a first input pin 19 of the microcontroller 18 and the overheat temperature connection 12 may be connected to a second input pin 20 of the microcontroller 18.

The controller 5 also includes a TRIode for Alternating Current (“TRIAC”) 21. The TRIAC 21 is an example of a control switch. The TRIAC 21 may also be known as a bidirectional triode thyristor or bilateral triode thyristor. The TRIAC 21 generally has three terminals: a first TRIAC main terminal 22; a second TRIAC main terminal 23 and; a gate TRIAC terminal 24. The gate TRIAC terminal 24 controls the current conducting state of the TRIAC 21 (open or closed circuit) between the first TRIAC main terminal 22 and the second TRIAC main terminal 23. When the TRIAC 21 is in a conducting state the circuit including the heater 14 and power supply 6 is closed; when the TRIAC 21 is in the non-conducting state the circuit is open.

The microcontroller 18 is connected to the gate TRIAC terminal 24 via a first output pin 25 of the microcontroller 18. The connection between the microcontroller 18 and the gate TRIAC terminal 24 of the TRIAC 21 may not be direct. However, the connection between the microcontroller 18 and the gate TRIAC terminal 24 of the TRIAC 21 is operable to control the conducting state of the TRIAC 21. That is, using the connection between the microcontroller 18 and the gate terminal 24 of the TRIAC 21, the microcontroller 18 can toggle the TRIAC 21 between conducting and non-conducting states. The microcontroller 18 may be configured to toggle the conduction state of the TRIAC 21 at a zero volt crossing point of the power supply voltage, which may improve electromagnetic compatibility.

The TRIAC 21 may be in contact with a housing of the controller 5. For example, via a thermal paste. This allows heat generated by operation of the TRIAC 21 to be effectively dissipated into the housing, which acts as a heatsink.

The controller 5 also includes a contactor 26. The contactor 26 is an example of an overheat switch. Other suitable examples include an electro-mechanical relay. The contactor 26 is capable of switching an electrical power circuit (e.g. 240V AC), the switching is typically controlled by a relatively low voltage circuit having a lower voltage (e.g. 5V DC). Schematically, the contactor 26 has three terminals: a first main contactor terminal 27; a second main contactor terminal 28 and; a gate contactor terminal 29. The microcontroller 18 is connected to the gate contactor terminal 29 via a second output pin 30 ofthe microcontroller 18. The connection between the microcontroller 18 and the gate contactor terminal 29 of the contactor 26 may not be direct. Alternatively, the connection between the microcontroller 18 and the gate contactor terminal 29 ofthe contactor 26 may be direct. However, the connection between the microcontroller 18 and the gate contactor terminal 29 ofthe contactor 26 is operable to control the conducting state ofthe contactor26. That is, using the connection between the second output pin ofthe microcontroller 18 and the gate contactor terminal 29 ofthe contactor 26, the microcontroller 18 can toggle the contactor 26 between conducting and non-conducting states (otherwise known as closed and open states, respectively). The connection from the microcontroller 18 may switch the relatively low voltage circuit of the contactor 26 to thereby switch the electrical power circuit. The contactor 26 is a “change over relay”, which means that upon power up ofthe controller 5, the contactor is energized to bring the contactor 26 into a conducting state. Should power to the contactor 26 be removed (e.g. if power is lost to the controller 5), then contactor 26 automatically opens into a non-conducting state, for safety.

The controller 5 is connected, in series, with the heater 14 and the power supply 6. Within the controller 5, the TRIAC 21 and the contactor 26 are also connected in series with the heater 14 and the power supply 6.

It will be appreciated that the controller 5 may be a distinct unit, separable from the oven 2. Thus the controller 5 may include terminals for connection to the power supply 6 and to the heating element 14 and to the control temperature sensor 9 and to the overheat temperature sensor 10.

The microcontroller 18 is configured to implement two components - a temperature control protocol 31 and a watchdog 32. The temperature control protocol 31 is configured to control the toggling ofthe TRIAC 21 based on the temperature measurement from the control temperature sensor 9. If the temperature in the chamber 8 exceeds a target temperature, as measured by the overheat temperature sensor 11, then the TRIAC 21 may be stuck in a conducting state and the temperature may be rising in the chamber 8 due to an overheat condition. If such an overheat condition is identified, the microcontroller 18 is configured to toggle the contactor 26 into a non-conducting state (operating according to the temperature control protocol 31). Thus, the circuit including the power supply 6 and the heater 14 is broken. The overheat condition is thereby prevented.

The watchdog 32 monitors the state ofthe microcontroller 18. For example, the watchdog 32 is able to determine whether the microcontroller 18 is in an error state. The watchdog 32 controls a watchdog output pin 33 ofthe microcontroller 18. The watchdog output pin 33 is connected to the contactor 26 via a watchdog output connection 34. The watchdog output connection 34 may be output from the controller 5 as a watchdog output. If and when the watchdog 32 determines that the microcontroller 18 is an error state, then, using a watchdog output signal on the watchdog output connection 34, the watchdog 32 is configured to toggle the contactor 26 into a non-conducting state using the gate contactor terminal 29. Thus, the circuit including the power supply 6 and the heater 14 is broken. This protects against an error in the microcontroller 18 in which the TRIAC 21 is retained in a connected state, and because the microcontroller 18 is in an error state, the contactor 26 has not be toggled into a disconnected state by the normal overheat operation of the microcontroller 18. An overheat condition indirectly caused by an error state in the microcontroller 18 is thereby mitigated.

When the watchdog 32 determines an error state in the microcontroller 18, the watchdog 32 may also restart the microcontroller 18.

The watchdog 32 may include a countdown timer. Normal operation of the microcontroller 18 includes resetting the timer before the countdown is complete. If normal operation of the microcontroller 18 ceases (i.e. during an error state), the countdown will not be reset. The countdown will thus complete (i.e. reach zero), whereupon the watchdog 32 determines an error state in the microcontroller 18. The countdown timer may count down from 1000 every millisecond, for example.

The microcontroller 18 may also be configured to place the contactor 26 and I or TRIAC 21 into a nonconducting state in the event of failure of one or both of the control temperature sensor 9 and the overheat temperature sensor 10.

The microcontroller 18 may also be configured to place the contactor 26 and I or TRIAC 21 into a nonconducting state in the event of disagreement on the temperature in the chamber 8 as provided by the control temperature sensor 9 and the overheat temperature sensor 10.

The microcontroller 18 may also be configured to place the contactor 26 into a non-conducting state in the event of a detection of a rising temperature in the chamber 8 when the microcontroller 18 is already attempting to maintain the heater 14 in a disconnected state via the TRIAC 21. In other words, when the TRIAC 21 should be in a non-conducting state but the temperature sensors 9, 10 nevertheless indicate that the temperature in the chamber 8 is rising, the microcontroller 18 places the contactor 26 into a nonconducting state.

In summary, under normal operating conditions, the microcontroller 18 is configured to switch the TRIAC 21 between conducting and non-conducting (connected and disconnected) states. This thereby toggles the state of the heater 14. As above, the microcontroller 18 obtains a control measurement of the temperature inside the chamber 8. By comparing the control measurement with a target temperature, the microcontroller 18 is configured to control the toggling of the heater 14 to substantially achieve the target temperature in the chamber 8.

In the event that an overheat condition is determined by the microcontroller 18 via the overheat temperature sensor 11, then the microcontroller 18 is configured to toggle the contactor 26 into a nonconducting state to thereby disconnect the heater 14 from the power supply 6.

In the event that the microcontroller 18 goes into an error state, the microcontroller 18 may not correctly toggle the TRIAC 21 or contactor 26. An error state may include the microcontroller 18 freezing or locking-up. Thus, an error state in the microcontroller 18 may result in the heater 14 being incorrectly controlled via operation of the TRIAC 21. Accordingly, if the heater 14 is erroneously maintained in an energized state then the temperature in the chamber 8 may exceed the target temperature. If the heater 14 is erroneously maintained in a disconnected state then the temperature in the chamber 8 may fall below the target temperature. Both scenarios are undesirable. The excess temperature is particularly disadvantageous since overheating may present a safety risk. The watchdog 32 serves to mitigate this issue.

As described above, the controller 5 controls a single power supply 6 and single heater 14. However, a high-power oven may use a three-phase power supply. Each of the three phases of the power supply is used to power one of three separate heaters in a chamber of the oven. To achieve such control an extension module for a controller for the temperature-controlled apparatus is provided.

Figure 4 illustrates a controller 5 connected to an extension module 40 according to a second embodiment. The extension module 40 in conjunction with a controller 5 described above allows a three phase power supply with three respective heaters to be used in a single temperature controlled apparatus, e.g. industrial oven. The controller 5 controls the first phase power supply, and the extension module controls the second and third phase power supplies. For example, a three phase power supply may have 3 x 240V A.C. Each phase can be used to power a 3 kilowatt heater, for example. That is one heater per “leg” or “phase” of the three phase power supply. In sum, the three heaters correspond to a single 9 kilowatt heater in an oven. Using a three-phase power supply, higher power ovens can be used.

The controller 5 operates according to the principles described for the controller 5 above. That is the controller 5 and a first heater 41 are connected in series with a first phase power supply 42. The controller 5 toggles the power supplied to the first heater 41. The first heater 41 generally corresponds to the heater 14 described in respect of the first embodiment. The first phase power supply 42 generally corresponds to the power supply 6 described in respect of the first embodiment.

The extension module 41 is connected to a second heater 43 and a second phase power supply 44. The extension module 40 is configured to toggle power to the second heater 43.

The extension module 41 is connected in series with a third heater 45 and a third phase power supply 46. The extension module 40 is configured to toggle power to the third heater 45.

The controller 5 is connected to a control sensor connection 11 and to an overheat sensor connection 12, as described in respect of the first embodiment.

The controller 5 and the extension module 40 are connected via interconnections 47. The interconnections 47 includes a second control line 48, a third control line 49, a watchdog line 50, and a ground line 51. The second control line 48 is connected to a second phase control pin of the microcontroller 18 of the controller 5. The second control line 48 is a first primary input 52 to the extension module (see Figure 5). The third control line 49 is connected to a third phase control pin of the microcontroller 18 of the controller 5. The third control line 49 is a second primary input 53 to the extension module 40. The watchdog line 50 is connected to the watchdog output connection 34, as described in respect of the first embodiment. The watchdog line 50 is a watchdog input 54 to the extension module 40. The ground line 51 forms a common ground between the controller 5 and the extension module 40.

Figure 5 shows a schematic illustration of the extension module 40 of Figure 4.

The extension module 40 controls the second heater 43 by toggling the connection to the second phase power supply 44. To do so, the extension module 40 includes first TRIAC 55, which is similar to the TRIAC 21 of the first embodiment. First primary input 52 is connected to the first gate TRIAC terminal 56. Recalling that the second control line 48 is ultimately connected to the microcontroller 18 of the controller 5, the microcontroller 18 is able to control the conducting state of the first TRIAC 55 via the first primary input 52.

The extension module 40 controls the third heater 45 by toggling the connection to the third phase power supply 46. To do so, the extension module 40 includes second TRIAC 57, which is similar to the TRIAC 21 of the first embodiment. Second primary input 53 is connected to the second gate TRIAC terminal 58. Recalling that the third control line 49 is ultimately connected to the microcontroller 18 of the controllers, the microcontroller 18 is able to control the state of the second TRIAC 57 via the second primary input 53.

The extension module 40 also includes a first contactor 59. The first contactor 59 is similar to the contactor 26 described in respect of the first embodiment. The watchdog input 54 is connected to a first contactor gate terminal 60 of the first contactor 59. Recalling that the watchdog line 50 is ultimately connected to the microcontroller 18 and is controlled by the watchdog 32, the watchdog 32 is able to control the state of the first contactor 59 via the watchdog input 54.

The extension module 40 also includes a second contactor 61. The second contactor 61 is similar to the contactor 26 described in respect of the first embodiment. The watchdog input 54 is connected to a second contactor gate terminal 62 of the second contactor 61. Recalling that the watchdog line 50 is connected to the microcontroller 18 and is controlled by the watchdog 32, the watchdog 32 is able to control the state of the second contactor 61 via the watchdog input 54.

As describes, the connection between each phase or leg of the three phase power supply and the respective heater is toggled by a respective contactor and respective TRIAC. There is thus no requirement for a 3-phase relay or for a 3-phase contactor, which provides for a controller 5 and extension module 40 with an uncomplicated and cost-effective construction.

Figure 6 illustrates a controller for a temperature-controlled apparatus according to a third embodiment of the present invention. The controller 5 of the first and / or second embodiments may operate in accordance with the third embodiment. However, it will be appreciated that the third embodiment may be implemented independently of the features of the first and second embodiments. Like elements from the first and second embodiments are numbered accordingly below.

Figure 6 illustrates an apparatus 1. The description of Figure 6 is similar to that of Figure 1, and is not repeated here. The temperature-controlled apparatus includes a controller 65. The controller 65 may correspond to the controller 5 above, or may be a different controller.

By virtue of the primary and overheat temperature sensors 9, 10, the controller 65 is configured to measure the temperature of the chamber 8. By control of the heater 14, and optionally the fan 16, the controller 65 is capable of controlling the temperature in the chamber 8. How the controller 65 operates to allow a user to control the temperature in the chamber 8 is the subject of the third embodiment.

Figure 7 shows a schematic of the controller 65 of Figure 6.

The controller 65 includes a microcontroller (not illustrated). The microcontroller is configured to implement three control protocols: a timer protocol 66, a real-time clock protocol 67, and a profile protocol 68. The controller 65 may be configured to implement one of more additional control protocols. The controller 65 may include controls to allow the user to instruct the controller 65 to operate according to any of the three control protocols 66, 67, 68 at any one time.

The timer protocol 66 implements a timer function. Using the timer function, the controller 65 is configured to control the heating element 14 and, optionally the fan 16, to achieve a target temperature in the chamber 8. When the target temperature is achieved in the chamber 8, the controller 65 is configured to maintain the target temperature in the chamber 8 for a user-selected time period. The controller 65 may be configured to begin to calculate an elapsed time from when the target temperature is first reached in the chamber 8. If the temperature falls below the target temperature by a drop temperature (e.g. by 2 degrees) before the elapsed time is equal to the user-selected time period, then the timer function may be configured to pause the timer that measures the elapsed time. The timer may be paused until the temperature returns to the target temperature. In that way, if the door to the chamber 8 is opened, for example, causing the temperature to drop for short period of time, then the user can be sure that the objects in the chamber 8 have nevertheless been exposed (e.g. cured) at the target temperature for the user-selected time-period. No time was lost at-temperature because of the door having been opened.

When the user-selected time period expires, the controller 65 is configured to allow the temperature in the chamber 8 to fall, for example, by disconnecting the power supply 6 from the heater 14. For example, operating according to the timer protocol 66, the user may instruct the controller 65 to achieve a target temperature of 100 degrees Celsius for 60 minutes (the user-selected time period).

The real-time clock protocol 67 implements a real-time clock (RTC) function. The controller 65 is configured to maintain the real-time (i.e. the time of day). That is, the controller 65 is configured to maintain at least the time of day, and may optionally be configured to maintain the date, and optionally the day of the week. Using the RTC function, the controller 65 is configured to place the oven 2 into a standby state based on the time of day and/or to bring the oven 2 out of standby state based on the time of day. Putting the oven 2 into the standby state may include putting the oven 2 into an OFF state. That is if the oven 2 is initially powered ON, then operating according to the real-time clock protocol, the controller 65 is configured to power OFF the oven 2 at 9pm, and to subsequently power ON the oven 2 at 8am the following day. For example, using the real-time clock protocol function, the oven 2 can be powered down overnight, thereby saving energy. The RTC function may be able to cycle the oven 2 between ON and OFF states more than once per day.

The profile protocol 68 implements a profile function. Under the control of the profile function, the temperature in the chamber 8 is substantially maintained according to a temperature profile.

Figure 8 illustrates an example temperature profile 69. In general, the temperature profile 69 is the target temperature in the chamber 8 as a function of time. In the example of Figure 8, the temperature profile 69 includes a sequence of temporal stages. Each stage is described by a number of stage parameters. The temperature profile 69 is the target temperature in the chamber 8, in degrees Celsius, as a function of time. Of course, the temperatures can also be measured and provided by the user in Fahrenheit. In the example of Figure 8, the temperature profile 69 includes five stages 70, 71,72, 73, 74. Each stage 70, 71,72, 73, 74 is defined by a stage temperature, a stage ramp, and a stage duration. The stage temperature is the temperature at which the chamber 8 should be maintained if stage ramp is equal to zero. In the event that the stage is one in which the temperature ramps up or down (i.e. stage ramp is non-zero) then the stage temperature is the temperature in the chamber at the commencement of the stage. In the event that the temperature in the chamber 8 is initially lower than the stage temperature of the first stage, then the controller 65 is configured to heat the chamber 8 to the stage temperature, and then commence the first stage. In the event that the temperature in the chamber 8 is initially above the stage temperature of the first stage, then the controller 65 will allow the chamber 8 to cool to the stage temperature, and then commence the first stage. The stage ramp is the rate of change of temperature per minute during the stage. The stage duration is the temporal length of the stage.

The stage parameters may also include a plurality of further control parameters. A first example further control parameter is whether or not the stage is at the end of the profile (the “End” Boolean variable below). If the stage is an End stage, then controller 65 may put the apparatus into a standby state at the conclusion of that end stage. A second example further control parameter is whether or not to trigger an event at the conclusion or start of the stage (the “Event” Boolean variable below). For example, an audible alarm or flashing light may be triggered at the conclusion or start of an event stage. A third example further control parameter is whether or not the oven is to pause the timer during a given stage should the temperature in the chamber 8 fall below the stage temperature by a drop temperature (for example, fall below the stage temperature by 10 degrees), then the timer function may be configured to pause the timer that measures the elapsed time for the stage. The timer may be paused until the temperature returns to the stage temperature. In that way, if the door to the chamber 8 is opened, for example, causing the temperature to drop for short period of time, then the user can be sure that the objects in the chamber 8 have nevertheless been exposed (e.g. cured) at the stage temperature for the stage duration.

In the example temperature profile shown in Figure 8, the stage parameters are as follows:

Stage 1,70:

Stage temperature:	50
Stage ramp:	+2
Stage duration:	25

Hold back:N

Event:N

End:N

Stage 2, 71:

Stage temperature:100

Stage ramp:0

Stage duration:20

Hold back:N

Event:N

End:N

Stage 3, 72:

Stage temperature:150

Stage ramp:5

Stage duration:10

Hold back:N

Event:N

End:N

Stage 4, 73:

Stage temperature:150

Stage ramp:0

Stage duration:30

Hold back:N

Event:N

End:N

Stage 5, 74:

Stage temperature:30

Stage ramp:-2

Stage duration:60

Hold back:Y

Event:Y

End:Y

In the above example, stages in which the temperature rises are “rising temperature” stages (e.g. Stages 1 and 3 above); stages in which the temperature declines are “falling temperature stages” (e.g. Stage 5 above), and; stages in which the temperature is maintained substantially constant are “constant temperature stages” (e.g. Stages 2 and 4 above). A particular profile may include fewer than or more than five stages.

In any or all of the control protocols, 66, 67, 68 the control of the heater 14 and I or fan 16 may be using a proportional-integral-derivative (“PID”) controller. Given a target temperature, and a current temperature from the primary temperature sensor 9, the PID controller controls the toggling of the power to the heater 14 and I or fan 16 to achieve the target temperature. In general, a PID controller is a control-loop feedback mechanism. In this case, the PID controller controls the heater 14 and I or fan 16, based on temperature feedback from the primary temperature sensor 9 to achieve the target temperature in the chamber 8. For example, the heater 14 may be toggled on and off as a rising temperature in the chamber 8 approaches the target temperature. This may prevent overshoot of the target temperature in the chamber 8 i.e. mitigate detrimental effects of hysteresis. The PID controller requires proportional, integral, and derivative values, denoted P, I and D values respectively. The controller 65 may include user controls, which permit the user to implement P, I and D values. The P, I and D values may depend on physical parameters of the temperature controlled apparatus. As such the manufacturer of the oven 2 and/or controller 65 may configure the controller 65 to use particular P, I and D values suitable for the apparatus with which the controller 65 is to be used.

The controller 65, using the overheat temperature sensor 11, also implements an overheat function. The overheat function may be configured to implement a band alarm function and / or a high-temperature function.

The band alarm function activates if the temperature measured by the overheat temperature sensor 11 is outside a band centred on the target temperature. For example, if the target temperature is 200 deg. C, and the band is 10 deg. C, then if the temperature as measured by the overheat sensor is greater than 205 deg. C or less than 195 deg. C, then the band alarm protocol may be activated.

When operating in the profile protocol 68, for example, the band is centred on the instantaneous target temperature. As such, unless accurate temperature control is in fact maintained in the chamber 8 during the temperature profile 69 (i.e. within band), the band alarm procedure will be activated. In this way, the user can be confident that the temperature profile 69 has been followed closely, and the oven 2 can be used reliably fortasks requiring accurate temperature control.

The high temperature alarm function activates if the temperature measured by the overheat temperature sensor 11 exceeds a maximum temperature, regardless of the instantaneous target temperature. For example, if the maximum temperature is 300 deg. C, and the temperature as measured by the overheat sensor 11 is greater than 300 deg. C, then a high temperature alarm procedure may be activated.

The band alarm procedure and I or the high temperature alarm procedure may each include one or more of:

Sounding an audible alarm;

Activating a visual cue (e.g. a warning light);

Presenting an alarm on the display;

Shutting-down the oven or putting the oven into a standby state;

Ceasing the current function, and I or

Notifying a user of the alarm.

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example +/-10%.

Claims

1. A controller for a temperature-controlled apparatus, the apparatus including a heating element for connection to a power supply, wherein the controller includes:

a control switch for connection in series with the power supply and the heating element;

an overheat switch for connection in series with the power supply and the heating element;

a microcontroller connected to the control switch to thereby toggle the control switch between conducting and non-conducting states;

wherein the microcontroller is configured to implement a watchdog configured to detect an error state in the microcontroller; and wherein the watchdog is configured to control a watchdog output of the microcontroller, and wherein the watchdog output is connected to the overheat switch to toggle the overheat switch into a nonconducting state upon detection by the watchdog of the error state in the microcontroller.

2. A controller according to claim 1, wherein the control switch is configured to disconnect the power supply from the heating element when the control switch is in the non-conducting state.

3. A controller according to claim 1 or claim 2, wherein the overheat switch is configured to disconnect the power supply from the heating element when the overheat switch is in the non-conducting state.

4. A controller according to any preceding claim, further including a watchdog connection between the overheat switch and the microcontroller, wherein the watchdog is configured to toggle the overheat switch into the non-conducting state by application of an overheat signal on the watchdog connection.

5. A controller according to any preceding claim wherein the microcontroller is configured for connection to a control temperature sensor and to an overheat temperature sensor.

6. A controller according to claim 5, wherein the control temperature sensor is configured to provide a signal representative of a control temperature measurement of the temperature-controlled environment to the microcontroller.

7. A controller according to claim 5 or claim 6, wherein the overheat temperature sensor is configured to provide a signal representative of an overheat temperature measurement of the temperature-controlled environment to the microcontroller.

8. A controller according to claim 7, wherein the microcontroller is configured to toggle the overheat switch into a non-conducting state when an overheat condition is detected by the microcontroller.

9. A controller according to claim 8, wherein the overheat condition is determined based on a difference between the overheat temperature measurement and a target temperature.

10. A controller according to any preceding claim, wherein the microcontroller is configured implement a temperature control protocol.

11. A controller according to claim 10 as dependent on claim 6, wherein the temperature control protocol includes toggling the control switch based on the control temperature measurement.

12. A controller according to any preceding claim, wherein the control switch includes a TRIode for Alternating Current (“TRIAC”)

13. A controller according to any preceding claim, wherein the control switch is in thermal contact with a housing of the controller.

14. A controller according to any preceding claim, wherein the overheat switch includes one of: a contactor or an electro-mechanical relay.

15. A controller according to any preceding claim, wherein the controller further includes a supplementary switch, and wherein the microcontroller is connected to the supplementary switch to toggle the supplementary switch between conducting and non-conducting states.

16. A controller according to any preceding claim, wherein the temperature controlled apparatus is an industrial oven.

17. A controller according to claim 16 wherein the supplementary switch is configured for connection to a fan in the industrial oven.

18. A temperature controlled apparatus including a controller according to any preceding claim.

19. An extension module for connection to a controller for a temperature-controlled apparatus, the apparatus including a first heating element for connection to a power supply, wherein the extension module includes:

a first control switch for connection in series with the power supply and the first heating element;

a first overheat switch for connection in series with the power supply and the first heating element;

a first control input to the extension module, the first control input connected to the first control switch, the first control input configured to receive a first control signal to toggle the first control switch between conducting and non-conducting states; and a watchdog input to the extension module, the watchdog input connected to the first overheat switch, the watchdog input configured to receive a watchdog signal to toggle the first overheat switch between conducting and non-conducting states.

20. An extension module according to claim 19, wherein the first control switch and first overheat switch are for connection in series with a first phase of the power supply.

21. An extension module according to claim 20, further including a second control switch and a second overheat switch for connection in series with a second phase of the power supply.

5

22. An extension module according to claim 21, further including a second control input connected to the second control switch, the second control input configured to receive a second control signal to toggle the second control switch between conducting and non-conducting states;

wherein the watchdog input is connected to the second overheat switch to toggle the second overheat switch between conducting and non-conducting states.

23. An extension module according to any one of claims 19 to 22, wherein the first control switch is in thermal contact with a housing of the extension module.

24. An extension module according to any one of claims 21 to 23, wherein the second control switch

15 is in thermal contact with a housing of the extension module.