Modular control unit

Abstract

A modular control unit 100 has a printed circuit board with card slots 110 inserted in each of which is an input-output card 120-1. The input-output cards 120_1 provide functionality to the modular control unit 100 where one input-output card 120_1 provides communication functionality and another input-output card 120_1 converts alternating current, AC or direct current DC, power received from an AC / DC power source to direct current, DC, power, and manages power delivery and power consumption of the modular control unit 100.

Description

Field of the Invention The present invention relates to a modular control unit, and a method of assembling the modular control unit. Background of the Invention Programmable Logic Controllers (PLCs) have been a cornerstone in industrial automation for decades, offering reliable control over various processes in manufacturing, energy, and infrastructure sectors. Traditional PLCs are typically programmed using ladder logic or proprietary programming languages, providing basic functionalities such as digital and analogue input-output control, timers, and counters. Several existing PLCs incorporate advanced features like Proportional Integral Derivative (PID) control, communication modules, and remote monitoring capabilities. However, despite their widespread adoption, traditional PLCs encounter flexibility, scalability, and remote connectivity limitations. The flexibility limitation results from traditional PLCs having fixed hardware configurations. This makes it challenging to adapt to evolving process requirements without significant reconfiguration or hardware upgrades. This limitation restricts their ability to accommodate specialized functions and customizations efficiently. Consequently, there is a need for control units which are more flexible, scalable, and secure to meet the evolving demands of modern industrial automation. Objects and aspects of the present claimed invention seek to alleviate at least these problems with the prior art. Summary of the Invention According to a first aspect of the invention, there is provided a modular control unit comprising: a printed circuit board, the printed circuit board comprising a plurality of card slots, a plurality of input-output cards each configured to slot into a card slot of the plurality of card slots; wherein the plurality of input-output cards are configured to provide functionality to the modular control unit; wherein a first input-output card of the plurality of input-output cards is configured to provide communication functionality; and wherein a second inputoutput card of the plurality of input-output cards is configured to convert alternating current, AC or direct current DC, power received from an AC / DC power source to direct current, DC, power, and further configured to manage power delivery and power consumption of the modular control unit. Advantageously, this provides a PLC which has increased flexibility (i.e. by allowing modular replacement of input-output cards the hardware may be upgraded and functionally extended or tailored for specific applications); increased scalability by not requiring third party modules to be used but instead using a plurality of input-output cards suitable for the modular control unit; increased remote connectivity by incorporating the second input-output card; and increased security by omitting third party modules which may introduce security loopholes. Furthermore, the presence of the first input-output card allows the modular control unit to send and receive data and commands wirelessly, allowing firmware upgrades, real-time monitoring and real-time control. It reduces or eliminates the need for wiring, leading to a reduction in costs and system complications. With respect to the scalability limitation, expanding the capabilities of traditional PLCs often involves integrating additional hardware modules, which can be cumbersome and expensive. Moreover, integrating third-party modules may introduce compatibility issues and require extensive programming efforts to ensure seamless operation. The first aspect of the present invention seeks to address this problem. With respect to the remote connectivity limitation, while some traditional PLCs support remote monitoring and control via Ethernet or proprietary protocols, their capabilities in this regard are often limited. Remote access features may not be inherently built into the PLCs, requiring additional hardware or software components for implementation, which can complicate system architecture and introduce security vulnerabilities. The first aspect of the present invention seeks to address this problem. Furthermore, traditional PLCs may lack robust security mechanisms to safeguard against cyber threats and unauthorized access. This has become a significant concern, especially with the increasing connectivity of industrial control systems to the Internet and cloud services. The first aspect of the present invention seeks to address this problem. In an embodiment, the first input-output card is configured to provide communication functionality. In an embodiment, the first input-output card is configured to provide communication functionality using a long term evolution system on a chip, LTE SoC, module. In a further embodiment, the LTE SoC is a simultaneous communication, SIM-COM, module. In an embodiment, the second input-output card of the plurality of input-output cards is further configured to distribute the DC power to the printed circuit board, the first input-output card, and any additional input-output cards slotted into the plurality of card slots. Advantageously, this provides a PLC that has increased flexibility by providing a modular card capable of efficiently distributing DC power to the other components of the modular control unit. In an embodiment, the plurality of input-output cards further comprise a third input-output card configured to determine a mechanical flow rate based on a pulse count received from an external flow meter. In a further embodiment, determining the mechanical flow rate comprises: determining a time elapsed between two consecutive pulses of a plurality of pulses received from the flow meter being received by the third input-output card; determining the flow rate using the determined elapsed time and a flow volume indicated by each pulse of the plurality of pulses. Advantageously, this provides an input-output card suitable for wastewater treatment by monitoring waste-water mechanical flow rates, allowing for the effective treatment of water. In an embodiment, the plurality of input-output cards further comprise a fourth input-output card configured to determine the pH level from an external pH sensor. Advantageously, this provides an input-output card suitable for wastewater treatment by monitoring waste-water pH levels, allowing for the effective treatment of water. In an embodiment, the plurality of input-output cards further comprise a fifth input-output card configured to monitor and debounce mechanical switches. In an embodiment, the plurality of input-output cards further comprise a sixth input-output card comprising a high-power solid state switch configured to turn contactors On and Off and provide one channel of feedback. In an embodiment, the plurality of input-output cards further comprise a seventh input-output card configured as a relay OV contact input-output card for switching devices with a universal input voltage range, which does not need to share a common voltage with the modular control unit. In an embodiment, the plurality of input-output cards further comprise an eight input-output card configured to determine readings from an external turbidity sensor, wherein the turbidity sensor is configured to monitor the turbidity of fluids and generate a turbidity sensor voltage for the turbidity sensor. Advantageously, this provides an input-output card suitable for wastewater treatment by monitoring waste-water turbidity, allowing for the effective treatment of water. In an embodiment, the printed circuit board comprises a memory unit. In an embodiment, the printed circuit board comprises shift registers, the shift registers configured to provide output signals from output pins on the printed circuit board. Advantageously, this provides a means of converting a small number of digital signals to many digital signals, providing many outputs necessary from the few available microcontroller pins of the printed circuit board. In an embodiment, the modular control unit comprises an external case to contain the modular control unit In accordance with a second aspect of the present invention, there is provided a method of assembly of the modular control unit in accordance with the first aspect, the method comprising the steps: (a) opening the external case; (b) placing the printed circuit board into the external case; (c) securing the printed circuit board inside the external case; (d) inserting the input-output cards in the card slots of the printed circuit board; and (e) closing the external case. Detailed Description of the Drawings The modular control unit (which may also be called the Envirohub control module (ECM)) in accordance with the present invention addresses the disadvantages described above by offering a modular and programmable PLC platform with enhanced communication capabilities and built-in security features. By leveraging customizable input / output cards for hardware upgrades, cloud-based monitoring, and remote firmware upgrades, the modular control unit provides a comprehensive solution for industrial control and monitoring applications. The limitations of the prior art stem from their fixed hardware configurations and limited support for third-party expansion modules. Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1A depicts an overhead plan view of a modular control unit in accordance with the present invention; Figure 1B depicts a lateral view of a modular control unit in accordance with the present invention; Figure 2A depicts a front view of a first input-output card configured to provide communication functionality in accordance with the first aspect of the invention; Figure 2B depicts a front view of an extension card of the first input-output card configured to provide communication functionality in accordance with the first aspect of the invention; Figure 3 depicts a second input-output card configured to convert alternating current, AC or direct current DC, power received from an AC / DC power source to direct current, DC, power, and further configured to manage power delivery and power consumption of the modular control unit in accordance with the first aspect of the invention; Figure 4 depicts a third input-output card configured to determine a mechanical flow rate based on a pulse count received from an external flow meter in accordance with an embodiment of the invention; Figure 5A depicts a front view of a fourth input-output card configured to determine the pH level from an external pH sensor in accordance with an embodiment of the invention; Figure 5B depicts a rear view of a fourth input-output card configured to determine the pH level from an external pH sensor in accordance with an embodiment of the invention; Figure 6 depicts a fifth input-output card configured to monitor and debounce mechanical switches in accordance with an embodiment of the invention; Figure 7 depicts a sixth input-output card comprising a high-power solid state switch configured to turn contactors On and Off and provide one channel of feedback in accordance with an embodiment of the invention; Figure 8 depicts a seventh input-output card configured as a relay OV contact input-output card for switching devices with a universal input voltage range, which does not need to share a common voltage with the modular control unit in accordance with an embodiment of the invention; Figure 9 depicts an eight input-output card configured to determine readings from an external turbidity sensor, wherein the turbidity sensor is configured to monitor the turbidity of fluids and generate a turbidity sensor voltage for the turbidity sensor in accordance with an embodiment of the invention; Figure 10 depicts a method of assembly of the modular control unit of the present invention, in accordance with a second aspect of the present invention; With reference to Figure 1A, there is depicted a modular control unit 100 in accordance with the present invention as seen from an overhead plan view. There is depicted a printed circuit board, the printed circuit board comprising a plurality of card slots 110. In each card slot of the plurality of card slots 110 there is shown an input-output card (120_1, 120_2, ...., 120_n) inserted into each slot 110. Although not shown, the input-output cards (120_1, 120_2, ...., 120_n) are removably connectable to the printed circuit board via the slots 110. Figure 1B depicts a modular control unit 100 in accordance with the present invention as seen from a lateral view and when the modular control unit 100 is inserted in an external case to contain the modular control unit 100. The modular control unit of Figure 1B is substantially the same as that depicted in Figure 1A, with the exception of the presence of an external case in Figure 1B. Figures 2A (and 2B) depict a front view of the first input-output card (and a front view of its extension card) in accordance with the first aspect of the invention. There is depicted a microcontroller unit (MCU) labelled U1 that is configured to receive instructions from the printed circuit board (herein also called the main-board, motherboard, or any other similar name) of the modular control unit. U1 receives instructions via an l2C bus (not shown) and it communicates with a SIM7600G-H LTE (not shown) module via a serial communication protocol. The l2C bus is an inbuilt communication channel within MCU (U1). Power control of the card is carried out in Q1 and Q2, where Q1 and Q2 have MOSFET switching capability to shut down power to the first input-output card when necessary. Female pin headers (J1 and J2 (shown in Figure 2A )) are provided to electrically connect the first input-output card to its extension card, which may be called CM02-4G upper, depicted in Figure 2B. A Peripheral Component Interconnect Express (PCIE) connector (J1), shown in Figure 2B, is configured to connect the SIM7600G-H LTE module to the extension card (CM02-4G upper). TheSIM7600G-H is a 4G / LTE module with GPS, MQTT communication, and HTTPS for firmware downloads. Components R1, R2, R3 and R7 are configured to perform pull-up functions. Components C3, C4, C5, C7 and C8 are configured to perform decoupling functions. The first input-output card of Figure 2A and 2B may further comprise an SD card switch chip (IC1), wherein IC1 is configured to connect and disconnect an SD card to U1 for firmware updates. The first input-output card may also further comprise a SIM card slot (J7), wherein J7 houses and connects a mini-SIM card to a SIM7600G-H LTE module (i.e. LTE module). There may also be a USB-C connector (J4) to allow a LISB-C device to be connected to the LTE module. There may also be programming contacts (TP1 to TP7) configured to allow the first input-output card to undergo a series of tests to be ready for usage, wherein an external test device may be used and connected to the first input-output card via TP1 to TP7. Figure 3 depicts a second input-output card in accordance with a first aspect of the present invention. There is depicted a full bridge rectifier (BR1) configured to ensure power from screwless terminal block (J4) has the correct polarity. There is depicted a 24V electronic fuse (E-fuse) is shown which is configured to limit the output current from the second card to 1.8A. The E-fuse is further configured to auto-restart if an electrical overload condition is cleared (e.g. if the current goes below 1.8A). The E-fuse is further configured to provide internal thermal monitoring. A start-up timer (IC1) (not shown) is utilised to enable to E-fuse on start-up of the second input-output card. Figure 3 further depicts a serial wire debug (SWD) connector (J3) configured to allow for a programming method (i.e. an alternative programming method to programming contacts TP1-TP7 discussed below). Consequently, the second input-output card is configured to be programmed using an SWD programmer, such as an Atmel In-Circuit Emulator (Atmel-ICE). A real-time clock (IC3) is depicted, wherein IC3 is configured to have an alarm output that inhibits the E-fuse from shutting down in normal conditions (i.e. when no electrical overload condition is cleared). IC3 is further configured to keep track of the time while the rest of the modular control unit is powered down. Components R10, C10 and D2 are a 2.7kQ resistor, a 100pF, 35V, 20% SMD / SMT capacitor, and a 3A Zener diode, respectively. The second input-output card of Figure 3 may further comprise an E-fuse enable-circuit (Q1 and Q3) configured to control the shutdown of the E-fuse if either the start-up timer or a realtime clock (RTC, such as IC3) does not require the E-fuse. The second input-output card may also further comprise seven programming contacts (TP1 to TP7) configured to be connected to an external programming device to program the second input-output card. The second input-output card may also further comprise a low current power supply (IC4), configured to power the RTC and a timer. IC4 may also power the RTC and a timer when the main 3.3V power supply is shut down. There may also comprise input voltage monitors (IC6 and IC7) configured to monitor the incoming voltage after rectification and pass the measured voltage to an MCU (U1). There may also be comprised an SD card switch chip (IC5) configured to connect and disconnect an SD card to the MCU (U1) for firmware updates. The second input-output card of Figure 3 further comprises a standard card edge connector (J2) configured to help the second input-output card to connect to a slot on the printed circuit board of the modular control unit. The second card may further comprise a 3.3V power supply (U2) configured to provide 3.3V power to core power rails of the modular control unit. MCU (U1) may communicate with the RTC to set or retrieve the time and the alarm settings, and it may also communicate with an analogue to digital controller (ADC) (IC6) for input voltage measurement with the core modular control unit via an l2C bus. Figure 4 depicts a third input-output card in accordance with an embodiment of the first aspect. The third input-output card is configured to provide hardware enhancement by enabling the modular control unit to perform flow rate control and measurement using a mechanical pulse count from an external flow meter. The third input-output card comprises an MCU (U1) configured to receive an incoming signal from a trigger inverter (IC2) to determine the flow rate and total flow. The resulting signal from IC2 is outputted via an l2C bus. Components IC4 and J2 are configured to perform signal conditioning by outputting a 3.3V signal, wherein the signal has a current limit of 0.165mA that is voltage-protected by D1. Signal pulses from the flow meter are received by IC2 via R5 which limits the current and defaults low with R7. The input signal is over voltage protected with diodes internal to IC2. A MOSFET (Q1) is shown and is configured with switching capacity to enable shutdown or complete power off the power supply to the third input-output card. The third input-output card comprises a standard edge connector (J1) configured to connect the third input-output card to the printed circuit board of the modular control unit. An SD card switch chip (IC1) is configured to connect and / or disconnect the SD card to the MCU (U1) for firmware updates. The third input-output card comprises an SWD connector (J2) as an alternative programming method allowing the card to be programmed through an SWD programmer, such as an Atmel-ICE. The third input-output card may further comprise a standard edge connector (J1) which is configured to connect to a slot of the plurality of slots on the printed circuit board of the modular control unit. In an example, the modular control unit may comprise programming contacts (TP1 to TP7) that are configured to make connections to an external programming device for programming the third input-output card. Figures 5A (and 5B) depict a front view (and rear view) of a fourth input-output card in accordance with an embodiment of the first aspect. The fourth input-output card is configured to enable the modular control unit to perform pH measurements and / or pH control. The fourth card comprises an MCU (U1) configured to receive input from an analogue to digital convertor (ADC), not shown, via a power and signal isolator (IC2), shown in Figure 5B. The ADC is a 24-bit differential analog with a low programmable gain amplifier, which measures the voltage from the pH sensor via an operational amplifier and is read by the MCU. The fourth card is configured to perform a linear (y=mx + c) transformation for calibration output. The fourth card is configured to communicate with the printed circuit board of the modular control unit via an l2C bus (not shown). For calibration, the fourth card is configured to auto-detect a buffer solution which provides a pH to mV calibration data point to allow for two-point calibration, with a central point removing offset, and the secondary point for determining the calibration gradient, using the linear transformation. The fourth card comprises an SWD connector (J1), as depicted in Figure 5A, configured to allow for an alternative programming method. For example, the fourth card can then be programmed using an SWD programmer, such as Atmel-ICE. A USB port (J2), as depicted in Figure 5A, is configured to provide an interface to allow for the debugging of the MCU. The fourth card comprises a standard edge connector (J3), as depicted in Figure 5A, configured to allow it to connect to a slot on the printed circuit board of the modular control unit. A MOSFET (Q1), as depicted in Figure 5A, is configured to provide power control to the fourth card. The MOSFET is configured to provide switching capacity to enable shutdown (i.e. complete power off) of power to the fourth card. A signal buffer (IC4), as depicted in Figure 5A, is configured to buffer the very low input current from the PH sensor to be read by the ADC. The fourth card further comprises an SD card switch chip (IC1), as depicted in Figure 5B, configured to connect and disconnect the SD card to the MCU (U1) for firmware updates. The fourth card comprises programming contacts (TP1 to TP7), as depicted in Figure 5B, that are configured to be connected to an external programming device to program the fourth card. The fourth card further comprises a power and signal isolator (IC2), as depicted in Figure 5B, configured to provide power and signal isolation between the MCU (U1) and the ADC (IC3) so that static voltages in the fluid in which the pH sensor is in do not affect the measured pH. Figure 6 depicts a fifth input-output card in accordance with an embodiment of the first aspect of the present invention. The fifth card comprises an MCU (U1) configured to receive input from a Hex Schmitt triggering inverter (IC2). The MCU (U1) is further configured to debounce a signal and output the debounced signal to the printed circuit board of the main control unit via an l2C bus. The inverter (IC2) is configured to receive an input from terminal J4, and it further comprises a signal clamping diode (Z1) to limit damage from overvoltage and output a clean signal to the MCU. The signal-cramping diode (Z1) is a Zener diode which in conjunction with R8 limits the output signal and prevents accidental overvoltage. A USB connector (J5) is configured for debugging of the MCU during development of a program which the MCU is configured to run. As with the first to fourth input-output card (and as with the sixth to eighth cards described below), the fifth card comprises an SD card switch chip (IC1, a standard edge connector (J1), a power control MOSFET (Q1), an SWD connector (J2), and programming contacts (TP1 to TP7). Figure 7 depicts a sixth input-output card in accordance with an embodiment of the first aspect of the present invention. The sixth input-output card comprises an MCU (U1) configured to receive input from the printed circuit board of the modular control unit via an l2C bus and outputs through a MOSFET switch chip. The MCU is further configured to accept input from a Hex Schmitt triggering inverter, debounce the signal, and outputs it to the printed circuit board of the modular control unit via the l2C bus. An output power switch chip (IC1) is configured to switch 24V DC power from the printed circuit board to the output terminal under the control of the MCU. As with the first to fifth input-output card (and as with the seventh and eight cards described below), the sixth card comprises an SD card switch chip (IC2), a standard card edge connector (J1), power control MOSFET (Q1), SWD connector (J2), USB connector (J3), Zener cramping diode (Z2), hex Schmitt triggering inverter (IC3), and programming contacts (TP1 to TP7). Figure 8 depicts a seventh input-output card in accordance with an embodiment of the first aspect of the present invention. The seventh input-output card comprises an MCU (U1) configured to receive input from the printed circuit board of the modular control unit through an l2C bus and produces outputs via a MOSFET switch chip. The MCU is further configured to accept input from a Hex Schmitt triggering inverter, debounce the signal, and outputs it to the printed circuit board of the modular control unit via the l2C bus. The seventh input-output card is similar to the sixth input-output card, and comprises an SD card switch chip (IC2), a standard card edge connector (J1), power control MOSFET (Q1), SWD connector (J2), Zener cramping diode (D3), hex Schmitt triggering inverter (IC3), and programming contacts (TP1 to TP7). Outlet relay (KI) is a latching relay controlled by the MCU via the MOSFETs Q2 and Q3. The output relay (KI) comprises fry-back diodes D1 and D2 on both coils. Figure 9 depicts an eighth input-output card in accordance with an embodiment of the first aspect of the present invention. The eighth card comprises an MCU (U1) that communicates with an RS485 turbidity sensor via the RS485 transceiver (IC2) and outputs to the printed circuit board of the modular control unit via the l2C bus. As with the other cards depicted in relation to Figure 1 to 8 and described herein, the eighth card comprises an SD card switch chip (IC1), a standard card edge connector (J 1), a power control MOSFET (Q1), an SWD connector (J2), a USB switch port (J5), and programming contacts (TP1 to TP7). The RS485 transceiver (IC2) converts transistor-to-transistor logic (TTL) levels to a standard RS485 differential signal. The eighth card also has a 5V DC power supply (PS1) that steps up (i.e. increases) the 3.3V signal from the printed circuit board of the modular control unit to a 5V DC supply for the turbidity probe (i.e. the turbidity sensor). Figure 10 depicts a method 800 of assembly of the modular control unit of the present invention, in accordance with a second aspect of the present invention. In particular, the method 800 comprises steps 810 to 850. Step 810 comprises opening the external case. Step 820 comprises placing the printed circuit board into the external case. Step 830 comprises securing the printed circuit board inside the external case. Step 840 comprises inserting the input-output cards in the card slots of the printed circuit board. Step 850 comprises closing the external case. In use, the skilled person would understand that an external case is not an essential element of the invention and that the essential element of the method 800 is found in step 840. In an embodiment, the method of assembly may comprise only step 840. It will be appreciated that the above-described embodiments of the first aspect of the present invention are given by way of example only, and that various modifications may be made to the embodiments without departing from the scope of the invention as defined in the appended claims.

Claims

1. A modular control unit, comprising:a printed circuit board, the printed circuit board comprising a plurality of card slots,a plurality of input-output cards each configured to slot into a card slot of the plurality of card slots;wherein the plurality of input-output cards are configured to provide functionality to the modular control unit;wherein a first input-output card of the plurality of input-output cards is configured to provide communication functionality; andwherein a second input-output card of the plurality of input-output cards is configured to convert alternating current, AC or direct current DC, power received from an AC / DC power source to direct current, DC, power, and further configured to manage power delivery and power consumption of the modular control unit2. The modular control unit of claim 1, wherein the first input-output card is configured to provide communication functionality using a long term evolution system on a chip, LTE SoC, module, for example a simultaneous communication, SIM-COM, module.

3. The modular control unit of claim 1, wherein the second input-output card of the plurality of input-output cards is further configured to distribute the DC power to the printed circuit board, the first input-output card and any additional input-output cards slotted into the plurality of card slots.

4. The modular control unit of claim 1, wherein the plurality of input-output cards further comprise a third input-output card configured to determine a mechanical flow rate based on a pulse count received from an external flow meter.

5. The modular control unit of claim 4, wherein determining the mechanical flow rate comprises:determining a time elapsed between two consecutive pulses of a plurality of pulses received from the flow meter being received by the third input-output card;determining the flow rate using the determined elapsed time and a flow volume indicated by each pulse of the plurality of pulses.

6. The modular control unit of claim 1, wherein the plurality of input-output cards further comprise a fourth input-output card configured to determine the pH level from an external pH sensor.

7. The modular control unit of claim 1, wherein the plurality of input-output cards further comprise a fifth input-output card configured to monitor and debounce mechanical switches.

8. The modular control unit of claim 1, wherein the plurality of input-output cards further comprise a sixth input-output card comprising a high-power solid state switch configured to turn contactors On and Off and provide one channel of feedback.

9. The modular control unit of claim 1, wherein the plurality of input-output cards further comprise a seventh input-output card configured as a relay OV contact input-output card for switching devices with a universal input voltage range, which does not need to share a common voltage with the modular control unit.

10. The modular control unit of claim 1, wherein the plurality of input-output cards further comprise an eight input-output card configured to determine readings from an external turbidity sensor, wherein the turbidity sensor is configured to monitor the turbidity of fluids and generate a turbidity sensor voltage for the turbidity sensor.

11. The modular control unit of any preceding claim, wherein the printed circuit board comprises a memory unit.

12. The modular control unit of any preceding claim, wherein the printed circuit board 5 comprises shift registers, the shift registers configured to provide output signals from output pins on the printed circuit board.

13. The modular control unit of any preceding claim, wherein the modular control unit comprises an external case to contain the modular control unit.io14. A method of assembly of the modular control unit of claim 13, comprising the steps:a) opening the external case;b) placing the printed circuit board into the external case;c) securing the printed circuit board inside the external case;15 d) inserting the input-output cards in the card slots of the printed circuit board; ande) closing the external case.16

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