Switches

Switches Overview
Whilst we are all aware of light switches and on/off switches on our home computers, devices and multimedia equipment, in electronics and electrical design engineering, switches as electronics components within an integrated circuit perform some of the most vital and fundamental functions within devices ranging from uses in almost every circuit in use today. Switches perform their role across domestic, industrial and commercial applications and within these fields are found within a huge range of products and equipment. The importance and value of switches is further demonstrated by the vast array of switch manufacturers, switch exporters and switch suppliers/distributors designing, producing, selling and using an equally vast range of types of switches for an eager and hungry marketplace.

What is a Switch (in Electronics)?
As electronics components, switches are used primarily to switch or break electrical circuits which interrupts the flow of current or moving the flow to another conductor, working as binary devices in either a closed position (on) or and open position (off) – it is this change of state from ON to OFF that is the function and property of an electrical switch that leads to its importance and vital role.

How do Switches work?
In circuits, a switch is basically made up of only two parts which are normally metal, these being the contacts, which are made of conductive material. Once these are connected to the circuit, then the circuit is completed, or closed, allowing the current to flow, whilst opening the switch breaks the circuit as the contacts have been separated by an insulating air gap, stopping the current from flowing. Closed contacts are also known as “make” and open contacts are known as “break”. It is important, therefore, for the contacts to be made from anti-corrosive materials with highly conductive properties also being key, as well as strength and cost. We may assume that all switches must be actually physically changed in their state by a person or operator but this is not the case in all situations as there are switches that can be effected by moving objects or by a connected sensor for temperature, pressure or flow. Some switches themselves can be operated by an electrical current, and these are known as relays. Relays can be with an electromagnet or it could be a solid state relay which uses an electronic component like a rectifier or triac to perform the switching state changes.

How the contacts are arranged is key to a switch and determines its function and classification – poles and throws are used to show these variations within a switch. The pole is the number of separate circuits being controlled by a single switch. A single-pole switch controls just one circuit. A double-pole switch controls two separate circuits. The throw is the number of separate output connections other than “open” that the switch can adopt for each pole. In a switch where the contacts remain in one state unless actuated, such as a push-button switch, the contacts can either be normally open (abbreviated “n.o.” or “no”) until closed by operation of the switch, or normally closed (“n.c.” or “nc”) and opened by the switch action. A switch with both types of contact is called a changeover switch. These may be “make-before-break” (“MBB” or shorting) which momentarily connects both circuits, or may be “break-before-make” (“BBM” or non-shorting) which interrupts one circuit before closing the other.  A single-throw switch is a simple on/off switch that connects or disconnects two terminals. When the switch is closed, the two terminals are connected and current flows between them. When the switch is opened, the terminals are not connected, so current does not flow. A double-throw switch connects an input terminal to one of two output terminals. A double-pole switch has three terminals. One of the terminals is called the common terminal. The other two terminals are often referred to as A and B.The part within the switch that actually applies the force to the contacts is the actuator, and may be a toggle or dolly, a rocker, a push-button or any type of electromechanical link.

Switch Type Abbreviations
SPST: Single-pole, single-throw (ON-OFF) switch
SPDT: Single-pole, double throw (ON-ON)
DPST: Double-pole, single-throw (ON-OFF)
DPDT: Double-pole, double-throw (ON-ON)
Any number of poles and throws can be added as required with the numbers and letters changing accordingly.
SPCO, SPTT, c.o: Single pole changeover or Single pole, centre off or Single Pole, Triple Throw
DPCO: Double pole changeover or Double pole, centre off.
Single pole/throw and double pole/throw switches are by far the most common switches, but triple and quadruple configurations are also seen in circuits.

Types of Switches
Even though there are a vast array of switch types, overall they can be classed as one of the following three types: Detection, Manual, Setting. Detection switches detect and determine the position of objects. Manual switches change state through a manual action. Setting switches are used to set the state for equipment and devices. From this overall classification taking the next step down leads to some of the following types of switches:

Acceleration
Basic / Snap Action
Biometric
Cable Pull
Coaxial
Coded Rotary
Control
Control Unit
Detector
DIL
DIP/SIP
Door Entry
Edge
Emergency Stop / E-Stop
Float
Foot
Illuminated
Interlock
Joystick
Key Operated
Keyboard
Keylock
Keypads
Latching PCB
Level
Limit
Magnetic/Reed
Microswitches
Modular
Multi-Directional
Pendulum
Piezo
Programmable
Proximity
Pull Cord
Pushbutton
Push-Button
Pushwheel
Reed
Rocker
Rotary
Selector
Slide
Switch Accessories
Switch Development Tools
TACT
Tactile
Thumbwheel
Thumbwheel & Pushwheel
Tilt
Tip-over
Toggle
Vandal resistant
Vibration
Voltage Select

Switch Industry Applications
Automotive
Aviation
Agriculture
Test & Measurement
Medical
Telecommunications
Industrial
Household
Security
Marine.

Electronics Products Containing Switches
Access Control
Alternative Energy
Amplifiers
Audio Equipment
Automotive
Boiler Controls
Broadcast Studio
Commercial and Institutional
Communications
Data Centers
Door Access
Door Entry
Drink Machines
Elevators
Factory Automation
Fire Alarm
Gaming Machines
Golf Trolley
Government and Military
Industrial
Industrial Test
Invalid Vehicles
Lamp Dimming
Lift Control
Light Level
Machine Building
Marine
Medical Devices
Medical Equipment
Metal Detectors
Mining
Mining Equipment
Oil and Gas
Personal Care
Power Supplies
Public Address
Recording Studio
Residential
Safety
Security Alarm
Security devices
Smart Grid
Speed Controller
Temperature Control
Theatre Lighting
Transportation
Utilities
Vending Machines
Weighing Systems

Switch Manufacturers in India List:
Lorlin
Salzer Electronics Limited
Hamilton Electronics Pvt. Ltd
Rico
Shruti Mechatronics
Maitry Instruments & Control
Electronic Switches India
Keetronics (India) Pvt. Ltd
essendeinki
Creative Electronics
Parasnath Electronics Pvt. Ltd
Sahni Electrical
Namolectric Controls
ALPS Electronics
Kaycee industries
Suraj Electronics and Electricals
Gilard Electronics Private Limited
S. D. Electronics Industries

Switch Manufacturers List:
Altech Corporation
Apem Components
Apex Tool Group/Cooper Tools
Arcolectric
Banner Engineering
Bi Tech
Bourns
Bulgin
C&K Components
Camdenboss
Carling Switches
Carling Technologies
Carlo Gavazzi Inc.
Cherry Electrical Products
Chily
Citizen
Comus
Copal
Crouzet Switches
CTS
Cynergy3 Components
Diptronics
Dwyer Instruments
EAO
Eaton Cutler Hammer
Eaton Moeller
Edwards Signaling & Security Systems
Eeco
Electroswitch Inc.
Elma
Erg Components
E-Switch
E-T-A Circuit Protection And Control
ETI Systems
Everel
GC Electronics
Grasslin By Intermatic
Grayhill
Hartmann
Hoffman
Honeywell
Hsi Sensing
Hubbell Wiring Device-Kellems
Ideal Industries
IDEC Corporation
IMO Precision Controls
ITW Switches
Johnson Electric
Keystone
Knitter-Switch
Krause & Naimer
Labinal Llc
Light Country
Linemaster
Lorlin
Lowe & Fletcher
Marquardt Switches
Master Appliance
Molex Incorporated
Multicomp
NCC
NKK Switches
NSF
NTE Electronics Inc.
Ohmite
Omron Electronic Components
Omron Industrial Automation
Otto Controls
Panasonic
Panasonic Electric Works
Pass & Seymour
Pic
Pico Technology
Piher
Power Dynamics
Rafi
Salecom
Schaffner
Schneider Electric
Schroff
Schurter
SCI
Siemens
Square D
Sti
Switchcraft
TE Connectivity
Telemecanique Sensors

This is part of the EEIND.in Wikielectronics, a Glossary of Terms and Components used in Electronics Systems, Design and Manufacture. We welcome your comments, thoughts and additions to this article – or indeed if you have a component or area of electronics design that you would like to submit an article into our Wiki, please email this to the site editor: editor1@eeind.in and we’ll take a look!

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