Electric Switch / Electric Switches

       A device which interrupts or turns on/off the flow of electrons or current in a circuit is called switch. The said device is said to be binary with respect to their function because it is capable of changing between two states, either completely on or completely off. It is a closed circuit if the switch is in the on state and an open circuit if otherwise in the off state. There are various types of switches and we shall distinguish them in this post or article.

When two materials which are electrical conductors are brought in contact with one another due to the movement of an actuating mechanism or by manually bringing those materials in contact with one another, a simple switch is made. There are, however, more complex types of switches, that contain electronic circuits that changes from on to off state and vice versa and dependent on some factors like light, magnetic field, motion, etc. Whatever may be the triggering factors for the switch, the end result of any switch will be at least a pair or pairs of wires which can be connected or disconnected to attain conduction of electricity or its opposite, a condition where no electricity flows through the circuit, or simply an open circuit.

Switches may be directly manipulated by human beings, such as the keyboard as in a case of control systems, or just simply to control the flow of current like in a light switch. There are also automatic switches which do not rely on human intervention in order to open or close the power in a given circuit. Such switches rely on certain variables or conditions like pressure, temperature, current, voltage, force, light, flow, and many others as triggering mechanism or stimulus.

Types of Electric Switch

1. Toggle Switches

       These types of switches are actuated by a lever inclined in one or more positions. To illustrate this, take for example a light switch. Most of the toggle switches stay or rest on its position when actuated but some contains an internal spring mechanism which allows it to return to its original or normal state once the lever is released. The latter type allows only momentary or temporary operation. Certain examples are the normally-open switch and the normally-closed switches.

2. Pushbutton Switches

       Pushbutton switches are devices which, when actuated, are capable to change between two positions upon a press and release of a button. Most of this type of switch has a spring mechanism located inside which enables the button to return to its original position after being pressed and released. Some pushbutton switch latches alternately on or off, while some other stay in the on or button remains “in” unless pulled back out. The latter type of pushbutton switch is oftentimes designed mushroom-shaped for convenience of a push and pull action.

3. Selector Switches

       This type of switch looks like a knob capable of rotation for easy selection of various positions or increments. Mostly, when rotated and switched to a particular position, remains in that position, while some are equipped with a spring mechanism which returns to the initial or pre-set position once the knob is released to ensure momentary operation.

4. Joystick Switch

       This type of switch is simply a lever which may be freely moved in different directions or axis. The output depends on how hard or how far the lever is pulled. A typical example is a joystick which enables the user to play games in a computer or any game console hardware.

5. Level Actuator Limit Switch

       There are certain switches which are designed specifically to function due to the movement of devices rather than by the operation of human intervention. These kinds of switches are oftentimes called limit switches. As the term suggests, limit switches restricts or limits the movement of the device or machine by shutting down the actuating power to a peripheral whenever the limit distance is reached. Limit switches are available in different varieties. They look like toggle or selector hand switches built for and fixed into a lever pushed by the device peripheral. The design, oftentimes, have levers containing small roller bearing at its end in order to prevent wear and tear due to constant and repeated movement of the machine or device.

6. Proximity switches

       Proximity switches function by sensing metallic machine part by using a magnetic field or by a high-frequency electromagnetic field. Some proximity switch uses a permanent magnet that triggers a sealed switch mechanism when a metallic device is close, usually one inch or less. Complex proximity switches function like a metal detector, which energizes a coil of wire using a high-frequency current and electronically keeping track of the magnitude of the said current. Whenever a metallic object comes into close proximity to the coil, the current rises and trips the monitoring circuitry.

7. Speed Switch

       This type of switch functions by sensing the speed of rotation of a shaft. This is possible either by a centrifugal weight mechanism which is mounted on the shaft, or by a type of detection of shaft motion like optical detection or magnetic detection. The latter type of detection is a non-contact detection mechanism.

8. Pressure Switch

       Pressure of air or liquid may also prove useful in actuating switches. This type of switches employs a design of converting the air or liquid pressure into mechanical force upon contact with the components of said switch like piston, diaphragm or bellows.

9. Temperature Switch

       A bimetallic strip or a thin strip composed of two metals which are connected together in a back-to-back manner but each metal reacts distinctly from the other when subjected to heat, may be used as a temperature sensing mechanism. This is a cost-effective type of temperature switch. Said switch functions whenever the temperature changes and such change in temperature could trigger one of the two metallic strips to react and bend, thereby causing it to actuate the switch from one state to another. Other innovations employ the use of brass bulb which is filled with a certain type of liquid or gas with a small tube interfaced to a switch sensitive to changes in pressure or other stimuli like heat. Once heated, the natural tendency for the gas or liquid is to expand followed by increased pressure, thereby actuating the switch mechanism.

10. Liquid Level Switch

       Another type of switch is the liquid level switch. As the name implies, this type of switch uses a floating object to actuate a switch mechanism as the liquid rises or falls in depth inside a specialized tank. If the nature of the liquid can conduct electricity, it can be utilized to conduct electricity between two metals in the tank at a specific depth. This is specially implemented with a design of relay which is triggered by a minimal current passing through the conductive liquid. Minimal current is used as it would be highly impractical and dangerous to implement this design using high level of current passing through the electrically conductive liquid.

11. Liquid Flow Switch

       This type of switch functions when gas or liquid contained and flowing inside a tank reaches a certain level, thereby pushing a small lever or vane. Said pushing mechanism actuates said switch. Other type of flow switches are designed as differential pressure switches, that is, the decrease in pressure is measured across a restriction located inside the pipe.