Manufacturers and basic models of controllers

Manufacturers and basic models of programmable logic controllers (PLCs)

Before you select a controller, you must make the main choice according to the number of input-output channels:

  • nano-PLC (less than 16 channels)
  • micro-PLC (16 - 100 channels)
  • middle (100 - 500 channels)
  • large (more than 500 channels)

Also you need to make a choice about the location of the input-output modules:

  • Monobloc controller, where the input-output device can’t be removed or replaced from one controller to another one.
  • Modular controller, which consists of common chassis, where the CPU module and removable input-output modules are located.
  • A distributed controller, so called CPU and removable input-output modules of are made in separated parts  and can be located at large distances.

More often there is a combination.

Next step is when you need to determine the architecture of programmable logic controller, it means, a set of its basic components and their relationships.

There are 3 main types of architecture of the PLC:

  • On ARM – is an advanced machine with a processor architecture, which increases performance by simplifying instructions to make the decoding them easier and time of performance - less; 32- and 64-bit microcontrollers.
  • AVR – a family of eight-bit microcontrollers.
  • PIC – a series of microcontrollers with separation of storages and instructions and data channels.

The main producers of ARM microcontrollers are: AMD, Apple, Analog Devices, Atmel, Xilinx, Altera, Cirrus Logic, Intel (until June 27, 2006), Marvell, NXP, STMicroelectronics, Samsung, LG, MediaTek, MStar, Qualcomm, Sony, Texas Instruments, nVidia, Freescale, Milandr, HiSilicon. In recent years, the greatest prevalence has ARM CortexM.

The representative of AVR microcontrollers is a well-known Atmel Company. Based on the need of the tasks are following families: AVR UC3; AVR XMEGA; megaAVR; tinyAVR; battery management; AVR microcontrollers for automotive electronics.

Microchip Technology Inc is a manufacturer of PIC PLC, they can be 8-, 16- and 32-bit. And they are used mainly for the expansion of peripheral input-output capabilities of microprocessors.

In recent years, a brand of hardware and software for the construction of simple automation systems and robotics widespread, focused on non-professional users, called the Arduino, which is a free program shell in the software part and a set of assembled printed circuit boards in the hardware with a fully open architecture system, ii means free copying and updating Arduino product line.

In the line of Arduino devices are mainly used the microcontrollers Atmel AVR ATmega328, ATmega168, ATmega2560, ATmega32U4, ATTiny85 with a clock frequency of 16 MHz or 8. There are also boards for the processor ARM Cortex M. Third-party developers have ported to Arduino support the popular Wi-Fi ESP8266 microcontroller.

There are a large number of expansion boards for the Arduino, which helps to implement various projects.

Among many manufacturers of 3D-printers including engineering professional developers (Ultimaker, Prusa, etc.) use the Arduino to implement its features.

There are also a large number of single board computers based on ARM architecture PLC. Their representative is the Raspberry Pi.

Types of probes and sensors

Probes and sensors, in fact have the same value, - measuring transducers, it means the element, which converts the signal to a controlled value, convenient for measurement, storage, transmission, processing, recording, and sometimes even to influence them on the controlled processes.

Depending on the magnitude of the input sensors we can distinguished: mechanical displacements, pneumatic, electrical, flow, speed sensors, acceleration, force, temperature, pressure, etc.

By type of output value, which is converted to the input value, we can distinguish non-electric and electric: Sensors DC (EMF or voltage), amplitude sensors AC (EMF or voltage), frequency sensors of alternating current (EMF or voltage), the resistance sensor (active, inductive or capacitive) and others.

By the principle of action the sensors can be divided into two classes: the generator and the parametric (modulators sensors). Generating sensors perform direct conversion of the input variable into an electrical signal. Parametric sensors convert input value into a change of an electrical parameter (R, L and C) sensor.

According to the principle of action the sensors can be divided into resistive, rheostat, photovoltaic (electro-optical), inductive, capacitive, and others.

There are three classes of sensors:

  • analog sensors, that is sensors which produce an analog signal proportionally to the change of the input value;
  • digital sensors, generating a sequence of pulses or binary word;
  • binary (binary) sensors that produce only two signal levels: "on / off" (that is, 0 or 1); It is widely used because of its simplicity.