Lecture 3: Switches

CSC 321: Embedded Sysytem

First Semester 2020/2021

Slide 1: Switches

A Switch is a device which is designed to interrupt the current flow of electrons in a circuit.

Switches are essentially binary devices: they are either completely on (“closed”) or completely off (“open”).

A Switch simply can make or break an electrical circuit.

Every electrical and electronics application uses at least one switch to perform ON and OFF operation of the device.

Switches are a part of the control system and without it, control operation cannot be achieved.

When the contacts of a switch are closed, the switch creates a closed path for the current to flow and hence load consumes the power from source.

Slide 2: Types of Switches

Toggle Switches

Toggle switches are actuated by a lever angled in one of two or more positions.

The common light switch used in household wiring is an example of a toggle switch.

Pushbutton Switches

Pushbutton switches are two-position devices actuated with a button that is pressed and released.

Most pushbutton switches have an internal spring mechanism returning the button to its “out,”

or “unpressed,” position, for momentary operation.

Selector Switches

Selector switches are actuated with a rotary knob or lever of some sort to select one of two or more positions.

Joystick Switches

A joystick switch is actuated by a lever free to move in more than one axis of motion.

One or more of several switch contact mechanisms are actuated depending on

which way the lever is pushed, and sometimes by how far it is pushed.

Pressure Switches

Gas or liquid pressure can be used to actuate a switch mechanism if that pressure is applied to a piston,

diaphragm, or bellows, which converts pressure to mechanical force.

Temperature Switches

An inexpensive temperature-sensing mechanism is the “bimetallic strip:” a thin strip of two metals,

joined back-to-back, each metal having a different rate of thermal expansion.

-- Isaac Armah-Mensah - 2021-05-25

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