Wiktor Wise
A switch is a device used to connect or disconnect an electrical circuit, allowing electricity to flow or cutting off the supply. Switches are typically either mechanical, electrical, electronic, or optical. They are usually manually operated, but can also be controlled electronically or automatically. They are a fundamental component of electrical engineering, allowing for the control of electrical circuits and the safe operation of machines.
Characteristics and Values of an Electric Switch
| Characteristics | Values |
|---|---|
| Function | To make or break an electrical connection in a circuit |
| Types | Toggle, push-button, hand switch, rocker, relay, latching relay, optical, etc. |
| Operation | Mechanically, electrically, electronically, or manually |
| Contacts | Normally open ("n.o." or "no") or normally closed ("n.c." or "nc") |
| Configuration | Multiple sets of contacts controlled by the same knob or actuator |
| Actuation | Alternate action (continuous "on" or "off") or momentary (push for "on", release for "off") |
| Usage | Control power flow, sense machine position, liquid level, pressure, temperature, etc. |
| Safety | Prevent accidental operation or electric shock |
| Ideal Characteristics | Zero voltage drop, rise time, and fall time; no limits on voltage or current rating |
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What You'll Learn
Switches can be mechanical, electrical, electronic or optical devices
In electrical engineering, a switch is a device that can disconnect or connect the conducting path in an electrical circuit, interrupting or diverting the electric current. Switches can be mechanical, electrical, electronic, or optical devices.
Mechanical Switches
Mechanical switches are the most common type of switch. They physically move a metal to either break or close a circuit. They are also known as physical switches as they require pressing or touching their contact. Mechanical switches can be manually operated electromechanical devices with one or more sets of electrical contacts, which are connected to external circuits. Each set of contacts can be in one of two states: closed, meaning the contacts are touching and electricity can flow between them, or open, where the contacts are separated and no current can flow. Mechanical switches can be further categorized based on several features, such as poles, throws, actuation, and the number of contacts. Examples of mechanical switches include toggle switches and push-button switches.
Electrical Switches
Electrical switches are operated by another electrical circuit and are known as relays. They can be used to isolate electric power from a system, providing a visible point of isolation. An ideal electrical switch would have no voltage drop when closed and would have no limits on voltage or current rating. It would also have zero rise and fall time during state changes and would change state without "bouncing" between on and off positions.
Electronic Switches
Electronic switches are a type of switch that uses semiconductor action to control the current flow without requiring any physical action. They are controlled electronically by active devices rather than purely mechanical means. Examples of electronic switches include capacitive switches, which are touch-sensitive and detect touch or proximity, and piezo switches, which use the piezoelectric effect to detect and generate electrical signals in response to mechanical stress or pressure.
Optical Switches
While not as common as the other types, optical switches are also used in certain applications. Optical switches use light beams to control the flow of electricity. They are often used in situations where physical contact is not possible or practical, such as in hazardous environments or where high speeds are required.
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They can open or close a circuit
An electric switch is a device that can open or close a circuit. It can also divert energy from one part of a circuit to another. In other words, it can connect or disconnect the conducting path in an electrical circuit, interrupting or starting the flow of electric current.
The most common type of switch is an electromechanical device with one or more sets of electrical contacts, which are connected to external circuits. Each set of contacts can be in one of two states: "closed" or "open". When the contacts are touching, electricity can flow between them (the "closed" state), and when they are separated, the switch is non-conducting (the "open" state).
The mechanism that transitions the switch between these two states is usually either an "alternate action" (flipping the switch for continuous "on" or "off") or "momentary" (push for "on", release for "off"). A switch may be directly manipulated by a human as a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch.
Push-button switches are generally configured as two-state switches, though they can also be designed with more than two states. Rocker switches, on the other hand, consist of a movable part that rocks back and forth and a fixed part that remains stationary. The switch toggles between two extreme positions, typically marked as "on" and "off".
Switches can also be categorised by the material of their housing. While most switch housings are made of plastic, metal may be used for certain applications, such as circuit breakers.
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Switches can be manually or automatically operated
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting or diverting the electric current. Switches can be manually or automatically operated.
Manual switches are typically electromechanical devices with one or more sets of electrical contacts connected to external circuits. Each set of contacts can be in a closed or open state. When the contacts are touching, electricity can flow between them, and when they are separated, the switch is non-conducting. Examples of manually operated switches include light switches, computer keyboard buttons, and limit switches. Limit switches are commonly used in machinery and can be activated by pressing a button or lever. They are often used to control machinery or equipment and work based on the movement or presence of an object.
On the other hand, automatic switches are designed to respond to specific conditions or events without human intervention. They can be operated by process variables such as pressure, temperature, flow, current, voltage, and force, acting as sensors in a process. For example, a thermostat is an automatic switch that controls a heating process based on temperature. Automatic switches are also used in applications like garage doors, where they detect the door's position and indicate when it is fully open.
Some switches can be remotely operated by a motor drive mechanism or controlled by another electrical circuit, known as a relay. Automatic switches are highly valuable to businesses and critical infrastructure that cannot afford extended periods without power. However, they tend to be pricier than manual switches.
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They can be used to control power flow in a circuit
In electrical engineering, a switch is a device that can connect or disconnect an electrical circuit, thus controlling the flow of electricity. Switches are usually manually operated electromechanical devices with one or more sets of electrical contacts. These contacts can be in one of two states: "closed", meaning the contacts are touching and electricity can flow between them, and "open", meaning the contacts are separated and no current can flow, acting as a non-conducting barrier.
The transition between these two states is actuated by a mechanism, which is usually of the "alternate action" type (flip the switch for "on" or "off") or "momentary" type (push for "on" and release for "off"). This mechanism allows for the control of power flow in a circuit, such as with a light switch. When the switch is in the "on" position, it completes the circuit, allowing electricity to flow through it. Conversely, the "off" position opens the circuit, creating a gap that electricity cannot cross, thus interrupting the power flow. This interruption in power flow can be used to protect electrical devices and users from potential dangers, such as overheating or electrical shocks.
Switches can also be automatically operated to control the motions of machines. For example, they can indicate whether a garage door is fully open or closed or whether a machine part has reached a specific position. Additionally, switches may be operated by process variables such as pressure, temperature, flow, current, voltage, and force, acting as sensors to automatically control a system. A thermostat, for example, is a temperature-operated switch used to control heating processes.
The operation of a switch relies on its ability to move between several predefined physical positions repeatedly and consistently over its lifespan. This may involve deforming the contactor, which must return to specific positions under mechanical loads applied by actuators. The contactor may be made of springy metal and exhibit bending or be made rigid and coupled with springs. To ensure safety, switches should be designed to handle specific amounts of electrical current, measured in amperes (A), to prevent short circuits.
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Switches can be used to sense machine part, liquid level, pressure or temperature
In electrical engineering, a switch is an electrical component that can connect or disconnect the conducting path in an electrical circuit, thus diverting electric current or interrupting its flow. Switches can be manually or automatically operated. They can also function as sensing elements to detect the position of a machine part, liquid level, pressure, or temperature.
Sensing Machine Parts
Limit switches are electromechanical devices used to detect the presence or absence of an object. They are often used to define the limit of travel of an object. For example, a limit switch is used to detect if a fridge door is open or closed, turning on the light when the door is opened.
Sensing Liquid Level
Liquid level sensors, also known as liquid level switches, are used to measure the level or height of a liquid or fluid in a container. They can be used to control and monitor the liquid level in a system and trigger alarms or shut-off valves when the liquid level is too high or too low. Optical liquid level switches, for instance, use an LED and phototransistor within the sensor housing to detect the presence of liquid. Ultrasonic sensors, on the other hand, measure liquid levels by calculating the duration and strength of high-frequency sound waves reflected off the surface of the liquid.
Sensing Pressure
Pressure switches are mechanical or electronic devices that are activated when a certain pressure threshold is reached. They are used to regulate pressure in a system or maintain a stable reservoir level. For instance, an air pressure switch can turn a compressor on or off to maintain the required air pressure in a tank.
Sensing Temperature
Temperature switches are used to control and monitor temperatures in various systems, switching an electrical contact when the temperature exceeds or falls below a certain level. This helps prevent overheating or ensures sufficient heating. Temperature switches with a bimetal are used in devices like compressors to switch them off in the event of excess temperature or to activate cooling mechanisms.
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Frequently asked questions
A switch is a mechanical, electrical, electronic, or optical device that can be used to open or close a circuit or divert energy from one part of a circuit to another.
There are many different types of switches, including toggle switches, push-button switches, rocker switches, and hand switches.
Switches work by either allowing two electrical conductors to make contact with each other or by breaking the connection. This is done through the movement of an actuating mechanism or by the use of electronic circuits that can respond to physical stimuli.
Examples of switches include light switches, computer keyboard buttons, and thermostats.
A normally open switch is in the "off" position until it is closed by the operation of the switch, while a normally closed switch is in the "on" position until it is opened by the switch action.
