Shri Sant Gajanan Maharaj College of Engineering Department

Shri Sant Gajanan Maharaj College of Engineering Department of Electronics & Telecommunications Engineering Electronic Devices & Components Unit – II Switches, Relays, Cables, Connectors, Heat Sink, Electronic Transformers Switches

What is a switch? Switches are commonly used to control circuits by either mechanical or electronic means.

Switch Definitions One moving contact One non-moving contact Single-Pole Single throw SPST – Single-Pole, Single-Throw switch (On-Off Switch)

What is function of a switch?

What are Poles and Throws – Pole refers to the number of completely isolated circuits that can be controlled by a switch. – Throw refers to the number of closed contact positions that exist per pole. • • SPST: single-pole, single-throw DPDT: double-pole, double-throw SPDT: single-pole, double-throw DPST: double-pole, single-throw

Three Basic Types of Switches

Toggle Switch

SPST Toggle Switch A Single Pole Single Throw (SPST) switch is a switch that only has a single input and can connect only to one output. This means it only has one input terminal and only one output terminal.

SPDT Toggle Switch A Single Pole Double Throw (SPDT) switch is a switch that only has a single input and can connect to and switch between 2 outputs. This means it has one input terminal and two output terminals.

SPDT Toggle Switch Application: Automobile Upper/Dipper Lamp Switch

Quiz: Identify the type of switch used

Quiz: Circuit that uses two SPDT switches Pictorial diagram of circuit is shown. Draw electrical circuit in your notebook.

Brain Storming Session A lamp near a stair case is to be made on by two switches. Lamp should light when either Switch #1 or Switch #2 is made ON. Draw the wiring circuit. The components given are: (01) Two SPDT switches (02) Battery (03) Lamp

Brain Storming Session Solution

DPST Toggle Switch A Double Pole Single Throw (DPST) switch is a switch that has 2 inputs and 2 outputs; each input has 1 corresponding output.

DPDT Toggle Switch A Double Pole Double Throw (DPDT) switch is a switch that has 2 inputs and 4 outputs; each input has 2 corresponding outputs that it can connect to.

Toggle Switch Specifications

Quiz : When will the buzzer ring? A car has electronic system to sound a buzzer. Observe the given Circuit. Write down a statement related to condition when the buzzer will ring?

What is Rocker Switch? • It is an on/off electronic switch that rocks (rather than trips) when pressed. This means that one side of the electric rocker switch is raised while the other side is depressed much like a seesaw or a rocking horse.

Rocker Switch Internal Mechanism

Rocker Switch Wiring Diagram Terminal Nomenclature

Some Rocker Switches

Some Rocker Switches( with LED indicator)

Features of Rocker Switches • Rocker switches are popular among gadgets like computer printers, UPS, SMPS etc. • Used solely for the purpose of shifting device operation from ON to OFF • Rocker switches can be engaged or disengaged with a small force • Rocker switches are available in various types and sizes like SPST, DPDT • They often come with a LED mounted beneath the actuator to indicate the ON state

Rocker Switch in a Circuit

Rocker Switch Specifications

Testing of Switches

Testing of Switches • Select ‘Continuity Tester’ function of Digital Multimeter • Connect Multimeter terminals across switch • If switch is OPEN, sound from buzzer will be heard • If switch is CLOSED, no sound will be heard

Testing of Switches • • Configure Digital Multimeter to act as Ohm Meter Connect Multimeter terminals across switch If switch is OPEN, DMM will show ‘over range’ i. e. 1 If switch is CLOSED, DMM will show zero resistance

Push-Button Switches Two types according to function (01) Momentary (02) Latching

Push-Button Switches

Push-Button Switches • Activate the switch by pushing a button • Two types of Push-Button Switches • Normally-closed (NC) – When the button is NOT pushed, the contact is closed • Normally-open (NO) – When the button is NOT pushed, the contact is open

Push-Button Switches Momentary Type

Push-Button Switches Operation

Push-Button Switches Momentary Type

Push-Button Switches Normally-Closed (NC) Normally-Open (NO)

Push-Button Switches Push to Break Push to Make

Push-Button Switches Push to Break Push to Make

Push-Button Switches Latching Type Push-to-Make, Push-to-Break

Push-Button Switches Applications • They can be operated instantly • Used in cameras, lifts • Telephone switch, Kitchen appliances • Emergency Exit, Door-open indicators

Push-Button Switches Applications

Push-Button Switches Applications

Push-Button Switches Specifications

Rotary Switches

Rotary Switch: Assembly

Rotary Switches

Rotary Switches

Assembly of Rotary Switch

Assembly of Rotary Switch

Assembly of Rotary Switch

Rotary Switches Its construction consists of three wafers or decks mounted on a common shaft. 51

Rotary Switches �A rotary switch operates with a twisting motion of the operating handle with at least two positions. �A rotary switch may have multiple levels or "decks" in order to allow it to control multiple circuits. �Rotary switches were used as channel selectors on television receivers until the early 1970 s, as range selectors on electrical metering equipment, as band selectors on multi-band radios and other similar purposes. �In industry, rotary switches are used for control of measuring instruments, switchgear, or in control circuits. 52

Rotary Switch Specification 53

Rotary Switch Applications • Example- Stereo input selector

Rotary Switch Applications • Radio frequency selection • Navigation and communication equipment • Precision test and measuring equipment • Sound mixing and editing consoles • Voice and data communications • Military radios, transmitters and receivers • Automotive climate control and entertainment systems • Musical instrument controls

Topic Beyond Syllabus DIP Switches

Topic Beyond Syllabus Keypad Switches

Topic Beyond Syllabus Linear Slide Switch