Joysticks. Joysticks are manual controllers for smoothly triggering devices and electrical machines in different directions. They are used where the direction of movement of the controlled object coincides with the direction of movement of the joystick. They are used for lifting and lowering objects or part of the controlled machine (crane, electric truck) or moving the actuator in a plane (by X and Y). They are also used in steel and construction industry, in managing metal working machines, transport and conveyor systems, robotic control, electro-hydraulic systems and so on.
Solenoid valves. Solenoid valves ensure control of fluids in various pipes using electromagnetic mechanism. There are direct and a membrane solenoid valves, with normally open and normally closed contacts. They are used in thermal engineering, mechanical engineering, chemical and food industry and in automating industrial processes.
Limit and mechanical position switches. Limit switches are reciprocal motion devices used for limiting the progress of various mechanisms. They have a lever system connected to one or more contacts. They are used as protection, interlocking, winders, belt conveyors, etc. They have normally open and normally closed contacts. They have mechanical movable parts and have both electrical and mechanical life. They have a contact button or an arm with a roll.
Level controllers. Level controllers are used to maintain the liquid level in a definite range. When the liquid level reaches a pre-defined upper limit, the level controller opens a valve. When the level falls to a pre-defined lower limit, a pump that restores the liquid level is activated. They are used for controlling the level in tanks, reservoirs, wells, etc.
Timers and time relays. Timers are used for switching on and off electrical circuits according to a preset time interval. Timers may be cyclic, i.e. repeating preset cycles, multifunctional, with delayed start, etc. They can also be electronic or electromechanical, which in turn may be motorized, quartz-mechanical, analog, etc. Just like the other components, they are used for automation of production processes.
Signal lights. Signal lights are an integral part of automated production and transport systems. There are different types of signal lamps – rotating, flashing, of different colors, some are connected with an alarm. They can be mounted on a command console or on the movable parts of the machine. Signal lights are also widely used in various roadworks or placed on special regime vehicles.
Means of signaling, alarms. In addition to various industrial, piezo and motor sirens, bells, horns and buzzers, this category is supplemented by broken glass detectors, panic buttons, smoke detectors with alarm. Buzzers, for example, are used for signaling when the headlights are on. They are also used as sound radiators in alarm systems and fire alarm devices. Buzzers consist of a piezoelectric plate, which, when electricity is supplied, oscillates with a high frequency and produces sound. Buzzers are programmed to emit a sound when a pre-set parameter is present or absent.
Temperature controllers. Temperature controllers are devices for measuring and maintaining the temperature, which are widely used in households and industry. They are used for automating manufacturing processes, for maintaining and monitoring the temperature of solids, liquids, gases and so on.
Their working method is based on comparing the temperature, measured by a thermo-sensor (most often a thermocouple or thermal resistance of type Pt100) with a value, which is pre- set by the user. If there is difference between the two values, the temperature controller activates an electric circuit at its output/outputs and triggers additional device/devices.
The basic principle of differentiating the automatic temperature regulators is the control algorithm. The basic and most commonly used ones in practice are four.
– Temperature controllers with two-position control algorithm: also known as ON/OFF. This is the simplest, but also the lowest level of precision method for measuring and control of temperature.
– Temperature controllers with three-position control algorithm: usually they trigger two relay outputs which manage multiple devices or enforce the same device in different operating modes.
– Temperature controllers with proportional control algorithm (P controllers): this control mechanism provides significantly higher precision, because the appropriate adjustment of the device can achieve gradual approximation of the regulated value to the preset one, while preventing its exceeding.
– Temperature controllers with proportional-integral-derivative control mechanism (PID controllers) – they achieve optimum precision and accuracy.
Photoelectric switches. Photo-sensors, also called photosensitive switches serve to automatically turn off outdoor lighting at reduced ambient light. They can be integrated into the luminaire itself or can be located in the vicinity. Their main component is a photo-sensor, which is responsive to light. Very often these photoelectric switches are used to control and activate street lighting in cities or illuminating parks, ports, railway stations, public areas of airports, barracks, storage areas, but also facades of single-family homes and villas, automatic lighting of shop-windows, etc.
This device can operate without human intervention and this is its main advantage. It is not affected by daylight saving time, it has very low own consumption and the more complex models have the option for sensitivity settings by a potentiometer. There are variations with an external sensor, linked to the actual switch through a cable, which allows the installation of the switch in the electrical panel, not outside in adverse weather conditions.
Frequency inverters. A frequency inverter is a device that converts the supplied voltage and frequency in alternating voltage and frequency. It is mounted between the power supply and the motor and allows a standard engine to become a flexible system with alternating-speed drive. There are also important additional benefits of using a frequency inverter in the system.
They are many and varied – beginning with the smooth engine start without increasing the inrush current; implementation of high-performance dynamic braking; raising of the cosφ, without using capacitors; significant reduction of energy costs for example in engines with alternating-load mode; in pumps and fans, where the mode of regulation of the fluid which they propel, is through various kinds of valves and shutters, wherein the power and respectively the energy consumption of the engine remains unchanged and a large part of the efficient power is lost for overcoming the barrier along the path of the fluid, but if a frequency inverter is used to control the speed of the electric motor, the power consumption is reduced in proportion to the pressure of the propeller, which leads to significant energy savings and we have full control over the operation of the motor – voltage, current, shaft speed, torque, acceleration time, stopping time, etc. Moreover, the smooth operation mode increases the service life of each component of the electrical equipment. And finally, another advantage is that there is possibility for overload protection.
Hydraulic and pneumatic switches. Pneumatic and hydraulic devices are used for building automation systems. The difference between a hydraulic switch and a pneumatic one is in the fluid with which they work. The hydraulic working fluid is a liquid, while the pneumatic devices operate with gases, such as steam, compressed air etc.
Encoders. Encoders convert angular values into electrical impulses that are read by electronic counters. They are used in the automation of metering and control devices, in automated design, etc.
Pressure switches. Pressure switches are mechanical devices for automatically controlling actuators, working under pressure. Pressure switches are devices that turn on and off certain circuits upon reaching a preset pressure. They are used in air-conditioning systems, steam engines and other systems, operating under pressure.
Contact and indicator gauges. Pressure gauges are devices for measuring the pressure of gases and fluids. They are divided into several groups.
– Indicator gauges, which only show the pressure in a particular part of the system;
– Contact gauges, which show the pressure, but also have the ability to keep a certain value within certain limits. They have the option for adjusting the upper and lower limit, each one being linked to a contact system, which switches a mechanism upon reaching the preset two pressure levels.
Electronic auxiliary automation equipment. These devices are the most versatile, that is why we will take a look at the most basic types.
– Electronic potentiometer. This is a microprocessor device for controlling regulators with analog input. Regulators are controlled through voltage, fed by thyristor DC drives, frequency inverters, etc.
– Process-indicator. This is a microprocessor device, intended to visualize the values of technological parameters;
– Unit for controlling magnetic valves. This device controls magnetic valves upon signalizing from a sensor and regulates the liquid level in tanks or bulk materials in warehouses.