Switch is an electro mechanical device, with one or more arrangements of electrical contacts mainly used in the electrical circuits. The switch working condition depends on two states they are open and closed.
- ‘Open-Switch’ means the contacts are separated, where the switch is in non-conducting state.
- ‘Closed-Switch’ means there are a contact both the ends, where the electricity can be passed into the switch.
- Between the two states (open and closed) the mechanism should be activated and transaction must take place. The transaction must be in toggle type or momentary type.
- Toggle type means ‘flip switch’ for on or off
- Momentary type means ‘push’ for on or off
- Switches are directly operated by a human to control the signal of a system. They are light switches, in circuits control power flow, in computer keyboard buttons etc.
- The automatically functioned switches are used to control the signal of machines, like to accept the position of the work piece in the machine tool and the door to reach the full open position of the garage.
- Switches are operated by the process variables known as temperature, pressure, current, flow, sensors, voltage, force etc. by using the variables they automatically control the system.
- For example the heating process is controlled by the temperature-operated switch in which thermostat acts. By using other electrical circuit the switch is operated, so the electrical circuit is called as
- By using the motor drive mechanism the large switches are operated by a remote.
- In some systems, separate electrical power switches are arranged, that provides a separate visible point that can be locked if required. This is to prevent unplanned operation of a device during repairs, plus to avoid from electric stock.
- When the ideal switch is closed, at that instance there is no voltage drop and also no limits on the current rating and the voltage.
- During the state change it would have the fall time and zero rise time, the change in the state between the on and off positions is done without
- Switches are available in various styles and they can operate by foot, hand or through the identification of object, level or pressure.
They are different types of switches they are:
Foot switches, wall switch, level switches, limit switches, toggle switch, membrane switches, push wheel or thumb wheel switch, pressure switches, rocker switches, slide switches, pull chain switches, rotary switches and push button switches etc.
The foot switches are electro mechanical devices. In the electrical circuits they are mainly used to control the power by the foot pressure.
Foot switch are frequently used on the machine to stabilize the work piece at that condition the operator needs a hand for the process. At the time of manufacturing they include the specifications like voltage rating, current rating, switching function and number of pedals required. We observe the foot switches where we cannot operate or control the cycle by hand. We can find the foot switches in office machines and hospital equipment’s.
Wall switches are also electro mechanical devices they are operated by hand. They are mainly used in the commercial building, residential for lighting control and also used to control the electrical outlets and ceiling fans.
At the time of manufacturing they include the specifications like actuator type, combination device function, and some more additional functions of the switch like fan speed control, timer based switching or dimmer control. The wall switches are designed separately to fit them inside the electrical boxes and to operate line voltage. Wall switches are standard items; they are used in commercial construction and residential purpose. We can see them in various styles and models.
Level switches are also electro mechanical devices. They are mainly used to identify the level of the fluids (liquids), solids and powders. Basically they are mounted on the hoppers, bins or tanks to provide an output to control system.
In some cases the level switches are used in the residential pumps, as they can activate the devices straightly. At the time of manufacturing they include the specifications like switch type, current ratting, and voltage ratting, measured media. We can see the application of level switch in the process industries to observer the hopper level and tank level. Level switches are used in the daily life application.
Limit switches are also electro mechanical devices. They are designed to sense location and motion automatically. To the controller it provides the output signal.
They are arranged on the factory floor and they are available as rugged enclosures and bare switches for the tough surroundings present in the industry. At the time of manufacturing they include the specifications like current rating, voltage rating and actuator type. Mainly the limit switches are used in the customer machines like washing machine.
Toggle switches are also electro mechanical devices. They are mainly used in the switching circuits. To the toggle switch lever is attached and is pressed into the small arc. When the level is moving in ‘to and fro’ motion then the electrical circuit opens and closes. The position of the lever gives the circuit status. At the time of manufacturing they include the specifications like single or double throw switching function, 1, 2, 3 axis configuration, or joystick configuration and type of the actuator. The toggle switches are mainly used in the electronics panel, switch boards etc.
The membrane switches are also electro mechanical devices. It provides the control of the process and machine without the help of any individual switch.
At the time of manufacturing they include the specifications like terminal type, assembly type and actuator type. The important features are display, no of keys, illumination and graphics. By using different switches they can use single device to reduce the cost.
Push wheel or thumb wheel switch
Push wheel switch is also known as the thumb wheel switch. It is also an electro mechanical device, used to control the rotatable wheel in the electrical circuits.
According to the position of the switch it displays the numerical value. At the time of manufacturing they include the specifications like actuator type, mounting type, coded output type, panel dimension and position. The thumb wheels are mainly used in instrumentation, flight controls and controllers. In computer devise they are used to test the measuring equipment’s.
Pressure switches are also electro mechanical devices. They are also used to sense the pressure of the fluid, as it provides the controller to the output signal. At the time of manufacturing they include the specifications like media measured, maximum and minimum switch current, pressure type, pressure connections, diaphragm material, maximum working pressure and minimum working pressure. In the lubrication system to maintain a particular pressure within the limits the pressure switch is used. In case of the excess pressure and over pressure it leads to the quick damage of the machine.
Rocker switches are also electro mechanical device. They are operated with the hand. Mainly the rocker switches are used in the switching circuits.
The position of the switch operator must be raised or depressed. We can observe the condition of the switch that must be on or off with the help of the visual indicator present on the circuit. At the time of manufacturing they include the specifications like single or double throw switching function, actuator type, mounting type, and panel dimensions. In many industrial controls rocker switches are used for the manual switching, for office maintenance and to control consumer goods.
Slide switches are also electro mechanical device. They are used on the switching circuits. The switch operator is in the form of the slider. The slider can move from one position to the other position to control the status of the circuit. At the time of manufacturing they include the specifications like single and double throw switching functions, panel dimensions and mounting types. The slide switches are mainly used in the electronic and electrical equipment, where the switching range must be limited. The slide switches are commonly used for on and off buttons and general switch.
Pull chain switches
Pull switches are also electro mechanical device. They are used on the switching circuits for on and off, or to increase the power level through a step circuit.
They are mainly used in the emergency stop drives. At the time of manufacturing they include the specifications like current rating, voltage rating and switching function. It performs the specific features to e-stop application like broken cable detection. The pull chains are used for manual control of overhead fans and lights.
Rotary switches are also electro mechanical device. They are used on the switching circuits and also selection of the function. The rotary switches have the multiple discrete stops and it can be made to turn-on and off in two positions. At the time of manufacturing they include the specifications like number of positions, number of poles, panel dimensions and mounting type. The rotary switches are used to provide a switch position, and it allows the operations like whether the circuit must be energized or not.
Push button switches:
The push button switches are referred to the push switches. They are also electro mechanical device. The switches are used for the switching circuits.
The push switches are the most common type of switches used in the control panel for the industry. At the time of manufacturing, they include the specifications like single or double throw switching function, mounting type, panel dimension, actuator type and contact type. The push button switches are used in the industries for controlling purpose, they are manufactured in bulk. They are available in different shapes and style.
Special type of switches
Mercury tilt switch
The mercury switch consists of a glass tube. The mercury must be in contact with the glass tube with two or more sides. When the glass tube is tilted at that stage the mercury passes through both end of the tube. The mercury switch gives better result when compare to the ball till switch. The liquid metal joining is not effected by the dirt, oxidation and fragments. At very low resistance the contacts must be wet for the safety purpose and free bounce connection, vibration and movement does not produce any poor contact, to get accuracy these type of process are used. The entire unit must be sealed to avoid accidents.
The knife switch consists of metal blade and it is pivot at one end. To the blade insulating handle is provided for the operation and it is a fixed contact. When the knife switch was closed, at that instance the current flows towards the pivot and blade, later it passes through fixed contact. The knife switches a basically enclosed. Usually the knife and the contacts are manufactured with the steel, brass and cooper, which mainly depend upon the application. The fixed contacts are backed up with the spring. By using one handle at a time several parallel blades are performed.
The parts are fixed with the help of insulating material on the base or directly mounted on the switch board with the help of bolts.
Thousands of amperes are carried with the help of knife switches, where they are manufactured in varies sizes and shapes. In the circuits gang operated switches are used to distribution and for transmission of electrical energy to the high voltages.
The double pole double throw switch consists of six connections. But there is common usage of double pole double throw where a polarity must be reversal. Some variations of the switches are internally wired for polarity reverse. The crossover switches have four terminals instead of six terminals. The four terminals are divided for two input and output. When the terminal is connected to the battery or DC source, at that instance the four ways switch is selected, either reversed or normal polarity. The lamps are controlled by using more than two switches where the intermediate switches are also used as switches.
Some more switches are in usage they are
Centrifugal switch, Dead man switch, kill switch, fireman switch, Hall-effect switch, isolator switch, inertial switch, light switch, latching switch, load control switch, membrane switch, piezo switch, pull switch , push switch, sense switch, RF matrix switch, transfer switch, touch switch, thermal switch, switch gear, electric switch board, slotted optical switch, time switch, Switch access and stepping switch.
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