The use of microcontrollers in industrial automation. Microcontrollers and single board computers versus plcs in industry. MSP43x Low Power Industrial Microcontroller Family
Modes of application of "TKM - 52" in APCS
The "TKM - 52" controller is designed to collect, process information and generate influences on the control object as part of distributed hierarchical or local autonomous process control systems based on the Ethernet or RS-485 (MODBUS) network. The controller can be used:
but as stand-alone device management of small objects;
b) as a remote terminal for communication with an object as part of distributed control systems;
c) simultaneously as a local control device and as a remote terminal for communication with an object as part of complex distributed control systems.
The controller in redundant mode is designed for use in highly reliable control systems. One of the operating systems can be installed in the controller, depending on the execution options: DOS or System Software (SSS) based on OS LINUX. In the first case, the IFC can be carried out using universal programming tools using the TRA - CE MODE program.
In stand-alone application, the controller solves problems of average information capacity (50-200 channels). It is possible to connect various peripheral devices via serial (RS - 232, HRS - 485) and parallel interfaces, as well as via Ethernet. The built-in keyboard and indicator block V03 can be used as the operator's panel.
In the mode of using a remote terminal for communication with an object, the control program is executed on a computing device of the upper hierarchy level (for example, on an IBM PC) connected to the controller via a serial channel (RS - 232 or RS - 485. Via the Modbus protocol), or via an Ethernet network , and the controller provides the collection of information and the issuance of control actions on the object.
Application in mixed mode (as an intelligent node of a distributed APCS), the object is controlled by an application program,
stored in the non-volatile memory of the controller. In this case, the controller is connected to the Ethernet network, which allows the computing device of the upper level of the hierarchy to have access to the values of the input and output signals of the controller and the values of the operating variables of the application program, as well as to influence these values. All free interfaces can be used in the controller, as well as its keyboard and indicator. Simultaneous execution of the application program and work over the Ethernet network is supported by means of the controller operating system and the I / O system.
This option makes the most of the resources of the TKM 52 controller, and allows you to create with its help flexible and reliable distributed APCS of any information capacity (up to tens of thousands of channels). This ensures the survivability of individual subsystems.
Controller composition and characteristics
The TKM-52 controller is a design-assembled item, the composition of which is determined when ordering. The controller consists of a base part, an indication keyboard unit and input-output modules (from 1 to 4). The base part of the controller consists of a housing, a power supply, a PCM423L processor module with a TCbus52 module and a V03 keyboard and display unit.
The body of the controller is made of metal and consists of sections connected with each other using special screws. The rear section houses the power supply and processor module. The rest of the sections house the I / O modules. The front section always houses a keyboard and display unit VОЗ. Depending on the number of sections for I / O modules, the following configurations of the base part of the controller are different:
The TKM - 52 controller operates from an alternating current with a frequency of 50 Hz and a voltage of 220 V, a power consumption of 130 W.
The TKM-52 controller is designed for continuous round-the-clock operation.
The operating temperature range of the environment controller is from plus 5 to plus 50 C. The controller has a dust-and-splash-proof version IP42.
Main characteristics of the processor module:
a) processor: FAMD DX-133 (5x86-133);
b) system RAM-8MB, depending on the installation of the memory module, it can be expanded up to 32 MB;
c) FLASH - memory of system and application programs - 4 Mb (can be expanded up to 144 Mb;
d) serial ports: COM1 RS232, COM2 RS232 / RS485 compatible UART 16550, parallel port LPT1: supports SPP / EPP / ECP modes;
e) Ethernet interface: Realtek RTL8019AS controller, software compatible with NE2000;
f) timer hard reset WatchDog, an astronomical calendar-timer powered by a built-in battery, power supply - 5 V ± 5%, 2 A.
Microcontrollers and single board computers offer developers a variety of options for automation applications, primarily in the flexibility of customization and the low cost of the solution. But can these elements be trusted in an industrial environment when used in equipment where trouble-free operation is critical?
The range of microcontrollers and mini-PCs that have emerged in the enthusiast world is expanding rapidly, without any reason waning. These components, including the Arduino, and the Raspberry Pi, offer extraordinary capabilities, including a vast ecosystem that includes an IDE, support, and accessories, all very cheap. Some of the engineers in some cases assume the possibility of using such microcontrollers in industrial automation devices instead of programmable logic controllers (PLCs). But is that wise?
Good question, but there is no need to rush to answer, as there is often a solution that may be obvious at first glance. Let's take a look below the surfaces and consider the factors relevant to the discussion. With a quick glance, we can see that there are about eighty different boards available on the market today, including microcontroller boards, FPGA boards and mini PCs with a wide range of capabilities. In this material, they will all be conventionally referred to as microcontrollers. Likewise, although PLCs have a wide range of capabilities, this material assumes a PLC with a well-designed and reliable controller.
Consider a small industrial process that requires two or three sensors and an actuator. The system communicates with a larger control system and a program must be written to control the process. This is no big deal for any small PLC that costs roughly $ 200, but it's tempting to use a much cheaper microcontroller. When developing, it looks for I / O peripherals first, there is no problem with the PLC, but it is probably a problem for the microcontroller.
Some microcontroller outputs are relatively easy to convert to, for example, a 4-20mA current loop interface. Others are slightly more difficult to convert, such as a pulse width modulated (PWM) analog output. A number of signal converters are available as standard products, but they add to the overall cost. An engineer insisting on complete do-it-yourself manufacturing can try to make the converter himself, but that commitment can be challenging and time-consuming to develop.
PLCs work, one might say, with any industrial sensor and generally do not require external conversion, since they are designed to connect to a huge variety of sensors, actuators and other industrial elements via I / O modules. The PLC is also easy to mount, and the microcontroller board with pins and connectors requires some wiring and alignment work.
A microcontroller is a "bare" device with no operating system or some simple operating system that needs to be customized for specific needs. After all, a $ 40 single board computer with Linux is unlikely to have a lot of embedded software capabilities, so the user is left to code all but the most basic capabilities.
On the other hand, even though the application is simple, the PLC has many built-in capabilities to do a lot behind the scenes without the need for special programming. PLCs have software watchdogs to keep track of the executable program and hardware devices. These checks happen on every scan with errors or warnings if a problem occurs.
In principle, each of these capabilities can be introduced into the microcontroller through programming, but the user will either have to write subroutines from scratch or find existing program blocks and libraries for reuse. Naturally, they need to be verified in the target application. An engineer writing multiple programs for the same controller can reuse pieces of code that have already been tested, but this capability is available in the operating system of almost every PLC.
In addition, PLCs are designed to withstand the demands of an industrial environment. The PLC is a rugged machine built and tested to withstand shock and vibration, electrical noise, corrosion and a wide temperature range. Microcontrollers often do not have such advantages. For microcontrollers, such detailed and thorough testing is rarely done, and usually these devices will include only the main requirements for certain markets, such as, for example, the control of household appliances.
It is also worth saying that many industrial machinery and equipment have been in operation for decades, so controllers are also required to work for a very long time. Therefore, users need long-term support. OEMs have a long-term responsibility to rely on the products they use in their devices and must be ready when a customer wishes to purchase replacement parts for a system that was introduced twenty years ago or earlier. Microcontroller companies may not be able to provide such a long life for their product. Most PLC manufacturers provide quality support, some even offer free technical support. However, it should be noted that microcontroller users often form their own technical support teams, answers to many questions are often found in discussion groups and forums with needs similar to your own.
Thus, microcontrollers and various types of development boards are more tools for learning, experimentation, and prototyping. They are cheap and make it much easier to learn complex programming and automation concepts. But at the same time, if the task is to make production work efficiently, and safely and without interruptions, PLCs provide wide range capabilities with reliability that has been tested and applied over a very long time. When a factory has to run smoothly and products have to be made with high quality and promptness on production lines, reliability and safety are most important.
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The industrial application of microcontrollers is very wide. These include decision automation, motor control, human machine interfaces (HMI), sensors, and programmable logic control. Increasingly, designers are integrating microcontrollers into previously "unreasonable systems," and the rapid proliferation of industrial IoT (Internet of Things) significantly accelerates the implementation of microcontrollers. However, industrial applications require lower electrical energy consumption and more rational use.
Therefore, microcontroller manufacturers are introducing their products into industrial and related markets, while offering high performance and flexibility, but with minimal power consumption.
Content:
Requirements for industrial microcontrollers
Typically, the industrial environment places increased demands on electrical equipment due to more severe operating conditions such as possible electrical noise and large surges in currents and voltages caused by the operation of powerful electric motors, compressors, welding equipment and other machines. Electrostatic and electromagnetic interference (EMI) and many others can also occur.
Low supply voltage and geometric processes of 130nm (cell density. Reached 2000-2001 by leading chip companies) or less prevent the above hazards from being handled. To eliminate possible emergencies, special external protection circuits are used, special boards that are located between the power section and "ground". If microcontroller manufacturers want to conquer the modern global market, they need to adhere to several requirements, which we will discuss below.
Low power consumption
Modern control and monitoring systems are becoming more and more complex, which increases the requirements for the implementation of processing in individual remote sensor units. Does this data need to be processed locally or use an ever-growing number of digital communication protocols? Most modern developers include a microcontroller in the measurement sensor in order to add additional functions to it. Modern systems include motor health monitors, remote sensing functions for liquids and gases, control valve controls, and more.
Many industrial sensor assemblies are far removed from power supplies, where a major drawback is the line voltage drop from the source to the sensor. Some sensors use a current loop where there is less loss. But regardless of the type of power supply, low consumption of the microcontroller is a must.
There are also battery-powered systems - building automation systems, fire alarms, motion detectors, electronic locks and thermostats. There are also many medical devices such as blood glucose meters, heart rate monitors, and other equipment.
Technologies do not keep pace with the ever-expanding capabilities of smart systems, which increases the need to minimize the energy consumption of system elements. The microcontroller should consume a minimum of electricity in the operating mode and be able to switch to sleep mode with minimum energy consumption, as well as wake up when given condition(internal timer or external interrupt).
The ability to save data
An important note about battery performance: any battery will sooner or later be discharged and cannot maintain the power output at the required level. Yes, if your mobile phone turns off in the middle of a conversation, it will cause irritation, but if a medical device turns off during an operation or a system in a complex production cycle, this can lead to very tragic consequences. When powered from the mains, the voltage may be lost due to a large overload or a line failure.
In such situations, it is very important that the microcontroller is able to calculate the shutdown situation and save all important operating data. It would be very nice if the device could save the states of the CPU, program counter, clock, registers, I / O state, and so on, so that after repeated operation the device can resume its work without a cold start.
Multiple communication options
When it comes to communication, gamut is controlled in industrial applications. At the same time, in wired communication, there are almost all types, ranging from the classic current loop 4 - 20 mA and RC-232 and ending with Ethernet, USB, LVDS, CAN and many other types of exchange protocols. As IoT gained popularity, wireless communication protocols and mixed protocols began to appear, for example, Bluetooth, Wi-Fi, ZigBee. In simple terms, the probability that this industry will settle on any one data exchange protocol is zero, so modern microcontrollers must accommodate a number of communication options.
Security
The latest version of the Internet Protocol IPv6 has a 128-bit address field, which gives it a theoretical maximum of 3.4x10 38 addresses. This is more than grains of sand in the world! With such a huge number of devices potentially open to the outside world, it becomes topical issue security. Many existing solutions are based on the use of open source software such as OpenSSL, however the results given use far from the best.
Several horror stories nevertheless took place. In 2015, researchers armed with a laptop and mobile phone hacked a Jeep Cherokee with wireless internet connections. They even managed to disengage the brakes! Naturally, this drawback was eliminated by the developers, but the danger remains. The possibility of hacking modern systems connected to the Internet keeps IoT experts in suspense, because if they were able to hack a car, then they can hack the system of an entire plant or factory, and this is much more dangerous. Remember Stuxnet?
Robust software and hardware security features such as AES encryption are a key requirement for modern industrial microcontrollers.
Scalable set of core options
A product that tries to satisfy all users will not satisfy anyone in the end.
Some industrial applications prioritize low power consumption. For example, a wireless monitoring system for recording the temperature in a food freezing system, or a strap-on sensor system for collecting physiological data. This system spends most of its time in sleep mode and periodically "wakes up" to perform a few simple tasks.
A large-scale industrial project will combine microcontrollers with various combinations of performance and power consumption. To speed up processing and speed up time to market, it should easily port application code between cores, depending on functional tasks.
Flexible set of peripherals
Considering the enormous scope of industrial control, processing and measurement, any industrial microcontroller family should have a minimum set of peripherals. Some of the "minimum set":
- Average resolution (10-, 12-, 14-bit) of analog-to-digital converters ADC operating at a speed of up to 1Msamples / s;
- (24-bit) high resolution for lower speeds for high-precision applications;
- Several options for serial communication, especially I2C, SPI and UART, but preferably USB;
- Security features: IP protection, Advanced Encryption Standard (AES) hardware accelerator;
- Built-in LDO and DC-DC converters;
- Specialized peripherals for general tasks such as touch capacitive switch module, LCD panel driver, transimpedance amplifier, and so on.
Powerful development tools
New projects are becoming more complex and require improvements and acceleration of development processes. To keep up with modern trends, any family of industrial microcontrollers must have full support in all stages of development and operation, which includes software, tools and development tools.
The software ecosystem should include a GUI IDE, operating room (RTOS), debugger, coding examples, code generation tools, peripheral settings, diver libraries, and APIs. There should also be support for the design process, preferably with online access to factory experts, as well as an online user chat where tips and tricks can be exchanged.
MSP43x Low Power Industrial Microcontroller Family
Several manufacturers have developed solutions to meet the demand of a growing market. One notable example of such manufacturers is Texas Instruments with its MSP43x family, which offers an excellent combination of high performance and low power consumption.
More than 500 devices are included in the MSP43x line, including even the ultra-low power MSP430 based on the 16-bit RISC core and the MSP432, which can combine high performance with ultra-low power consumption. These devices have a floating point 32-bit ARM Cortex-M4F core with up to 256KB flash memory.
The MSP430FRxx is a family of 100 devices utilizing ferroelectric random access memory (FRAM) for unique performance capabilities. FRAM, also known as FeRAM or F-RAM, combines the functions of flash and SRAM technologies. It is non-volatile with fast writing and low power consumption, 10-15 cycles write endurance, improved code and data security compared to flash or EEPROM, as well as increased resistance to radiation and electromagnetic radiation.
The MSP43x family supports a variety of industrial and other low power applications, including network infrastructure, control processes, test and measurement, home automation, medical and fitness equipment, personal electronic devices, and many others.
Ultra-low power example: Nine-axis sensors combined with the MSP430F5528
In exploration and measurement in applications, an increasing number of sensors “merge” into a single system and use common software and hardware to combine data from multiple devices. Fusion of data corrects individual deficiencies of sensors and improves performance in determining position or orientation in space.
The diagram above shows a block diagram of an AHRS that uses a low power MSP430F5528 plus a magnetometer, gyroscope and accelerometer in all three axes. The MSP430F5528 optimizes and extends the battery life of a portable meter containing a 16-bit RISC core, hardware multiplier, 12-bit ADC and multiple serial modules including USB.
The software uses a direction-cosine-matrix (DCM) algorithm that takes calibrated sensor readings, calculates their orientation in space, and outputs the values as elevation, roll, and yaw called Euler angles.
If required, the MSP430F5xx can communicate with motion sensors via a serial I 2 C protocol. This can benefit the entire system, since the main microcontroller is freed from processing information from the sensor. It can stay in standby mode, thereby reducing power consumption, or use the freed up resources to solve other tasks, thus increasing system performance.
High Performance Application Example: BPSK Modem Using MSP432P401R
Binary Phase Shift Keying (BPSK) is digital circuit modulation, which conveys information by changing the phase of a reference signal. A typical application would be an optical communications system that uses a BPSK modem to provide an additional link for low data rate signals.
BPSK uses two different signals to represent binary digital data in two different modulation phases. The carrier of one phase will be bit 0, while the phase shifted by 180 0 will be bit 1. This data transfer is shown below:
The MSP432P401R forms the core of the design. In addition to a 32-bit ARM Cortex-M4 core, this device has a 14-bit, 1-Msps ADC and CMSIS digital signal processing (DSP) library, which allows it to efficiently handle complex digital signal processing functions.
The transmitter (modulator) and receiver (demodulator) are shown below:
Implementation includes BPSK modulation and demodulation, forward error correction, error correction to improve BER, and digital signal shaping. BPSK includes an optional finite impulse response (FIR) low-pass filter to improve signal-to-noise ratio (SNR) prior to demodulation.
BPSK modulator characteristics:
- carrier frequency 125 kHz;
- bit rate up to 125 kbps;
- Full packet or frame up to 600 bytes;
- x4 media oversampling at 125 kHz (i.e. 500 ksps sampling rate)
conclusions
Microcontrollers for industrial use must have a combination of high performance, low power consumption, flexible feature set, and a powerful software development ecosystem.
Among the various branches of the domestic industry, the most in demand is the sphere of industrial automation. Almost any type of production requires a huge number of components to automate certain production processes. Ultimately, each manufacturing enterprise is interested in the management process technological processes was carried out promptly and automatically.
The heart of any automatic control system (ACS) is an industrial controller.
Historical reference
The first industrial controller appeared in 1969 in the USA. Its creation was initiated by the automobile corporation General Motors Company, and developed by Bedford Associates.
In those years, ACS were built on rigid logic (hardware programming), which made it impossible to reconfigure them.
Therefore, each technological line required an individual automated control system. Then, in the architecture of the ACS, devices began to be used, the algorithm of which could be changed using relay connection diagrams.
Such devices are called "industrial logic controllers" (PLC). However, automated control systems implemented using electromagnetic relays were complex and large in size. A separate room was required to house and maintain one system.
The microprocessor PLC developed by engineers of Bedford Associates (USA) made it possible to use information Technology in the automation of production processes, while minimizing the human factor.
Modern industrial controller
In general terms, a PLC is a microprocessor device that switches the connected signal wires. The required combinations of their connection are set by the control program on the computer screen and then entered into the controller's memory.
Programming is carried out both in classical algorithmic languages and in languages specified in IEC 61131-3 standards. Thus, it became possible for enterprises to implement various automated control systems using one microprocessor device.
Over time, the developers of industrial automation systems switched to an element base compatible with IBM computers (PCs). There are two directions in the development of PC-compatible hardware with PLCs, in which the architecture and design solutions are preserved as much as possible:
- PLC - with the simultaneous replacement of its processor module with a PC-compatible module with an open software(ADAM5000 series of controllers).
- IBM PC - in small-sized embedded systems (modular PC104 and micro PC controllers).
Therefore, modern PLCs are a PC-compatible modular controller designed for solving local control tasks. Their development should ultimately lead to:
- reduction in overall dimensions;
- expanding functionality;
- the use of a single programming language (IEC 61131-3) and the ideology of "open systems".
Principle of operation and scope of PLC
Any kind of PLC is electronic device designed to execute control algorithms. The principle of operation of all PLCs is the same - the collection and processing of data and the issuance of control actions to the actuators.
PLCs are widely used in industry. This explains the existence of a large number of their varieties, among which controllers can be distinguished:
- General industrial (universal).
- Communication.
- Designed to control positioning and movement, including robots.
- With feedback (PID controllers).
PLC classification
There are a large number of parameters by which PLCs are classified.
Constructive performance:
- monoblock;
- modular;
- distributed;
- universal.
Number of I / O channels:
- nano-PLC, with less than 16 channels;
- micro-PLC (16 ... 100 channels);
- medium (100 ... 500 channels);
- large, with more than 500 channels.
Programming methods.
PLCs can be programmed with:
- front panel of the device;
- using a portable programmer;
- using a computer.
Types of installation.
- rack-mount;
- wall;
- panel (installed on a cabinet door or a special panel);
- on a DIN rail (installation inside the cabinet).
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Microcontrollers vs. PLCs: There is a clear winner in the battle for your industrial applications.
The world of single board computers and microcontrollers offers interesting and inexpensive opportunities for automation applications, but can these components be trusted for mission-critical production applications where are PLCs traditionally used?
The range of microcontrollers appearing in the world is growing rapidly and there are no signs of decline. These devices - including the Arduino, BeagleBone, Raspberry Pi, and others - offer exceptional capabilities. They can also offer entire ecosystems of accessories, all at very low prices.
Bill Dehner, Technical Marketing Engineer; and Tim Wheeler, technical marketer and development instructor at AutomationDirect; wrote an article titled Microcontrollers vs. PLCs: Which One Is Leading Your Enterprise ?, which came out in November 2017 in Control Engineering. They discussed how interest in these products has grown, to the point that some are considering using these microcontrollers for industrial automation applications instead of PLCs. But is it reasonable?
This is a natural question, but the answer must be approached with caution, because often more depends on such a decision than it might seem at first glance. Let's take a look below and see factors relevant to the discussion.
After a quick online survey, we can see that there are about 80 different boards, including microcontrollers, FPGA boards, and single board computers, with a wide range of capabilities. In any case, in this blog, we will combine them all together and call them microcontrollers.
Likewise, even though PLCs have a wide range of capabilities, we will think of PLCs as some kind of generic and reliable controller such as the AutomationDirect BRX.
Hypothetical example
The article discusses a small automated process that requires two or three sensors and a drive. The system interacts with a larger control system, and a program must be written to control the process. This is an easy task for any small PLC under $ 200, but would like to use a much cheaper microcontroller.
The first step is to look for I / O - not a PLC problem, but possibly a microcontroller problem.
“Some (microcontroller outputs) are relatively easy to convert, such as a 4-20 mA current loop to 0-5 V. Others are more difficult to convert, such as an analog output using pulse width modulation (PWM), this is generally for microcontrollers. Some signal converters are available as standard products, but they add to the overall cost. A full-time DIY engineer might try to build the converter internally, but this can be difficult and time-consuming to develop. ”
PLCs work with almost any industrial sensor, and generally do not need external conversion as they are made to connect to a wide variety of sensors, actuators, and other industrial components through their I / O. The PLC is easy to mount, while the microcontroller board with pins and connectors takes a little work.
OS
Dehner and Wheeler point out that the microcontroller is a skeleton device with an underlying operating system. “After all, a $ 40 single board computer isn't going to have a lot of built-in software routines. Therefore, the user is left to encode everything but the most elementary possibilities. "
While the application can be simple, the PLC has many built-in capabilities. The PLC makes the events happening behind the scenes invisible and does not require user programming, unlike the situation when a microcontroller is used. The PLC has software watchdog timers to keep track of the program being executed and hardware watchdog timers to monitor modules and I / O devices. These checks occur on every scan cycle, with error or warning alerts when a problem occurs.
“In theory, any of these capabilities could be added by programming the microcontroller, but the user would either have to write procedures from scratch or find existing software modules to reuse. Naturally, they must be tested and verified for the application, and the importance of such testing must be understood, at least the first time. An engineer writing multiple programs for a single controller can probably reuse tested blocks of code. But these possibilities are already included in operating system for almost any PLC. "
PLC means production reliability
PLCs are designed to withstand the demands of an industrial environment. The equipment is reliable and made and tested to withstand shock and vibration, electrical noise, corrosion and a wide temperature range. Otherwise with microcontrollers.
“Microcontrollers rarely go through such extensive testing and tend to include only the basic requirements for specific markets such as office equipment. Even these requirements may not be met in the case of an unknown motherboard manufacturer. The generic board may not have been tested to the same extent as the branded board, even if it appears to be identical. "
Technical support
A lot of industrial equipment has been running nonstop for decades, so controllers must function smoothly as well. As a result, users need long-term support.
“Original equipment manufacturers have to look at the products they use on their machines and have to be ready when a customer wants to buy parts for a system installed in the 1990s or even earlier.
Microcontroller companies cannot keep this link of history. If you need to replace a controller for a project five years ago, finding the parts you need can be a challenge. ”
Most PLC vendors have excellent support capabilities, with some, such as AutomationDirect, offering free technical support. However, end-users of microcontrollers with open source code often create their own technical support teams. Answers to questions can often be found in discussion groups and topic forums with needs similar to yours. Or not.
Summarizing
“Microcontrollers and other types of development boards are fantastic as teaching tools and for experimentation. They are cheap and make complex programming and automation concepts much easier to learn. ” If you have the time, these are great tools.
“On the other hand, if the challenge is to operate efficiently, efficiently and safely in manufacturing, then PLCs provide a wide range of capabilities with reliability that has been tested and used for decades. When a plant has to work and products have to be manufactured, reliability and safety are more important than anything else. ”