This document provides an overview of mechanical switches used in mechatronics. It describes different types of mechanical switches classified based on number of contacts and poles, including single pole single throw (SPST), single pole double throw (SPDT), double pole single throw (DPST), and double pole double throw (DPDT) switches. It also explains common switch types like push button and toggle switches, describing their basic operation and use in circuits.

1. MEHRAN UNIVERSITY OF
ENGINEERING AND
TECHNOLOGY JAMSHORO
Overview of Mechanical
Switches
Mechatronics
Presented by: Mudeer
Ahmed F16ME33
Kashif Ali (F16ME166)

2. INTRODUCT
ION
A switch is a device which is designed to
interrupt the current flow in a circuit, in
other words, it 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.

3. MECHANIC
AL
SWITCHES
Mechanical switches can be classified into
different types based on several factors such
as method of actuation (manual, limit and
process switches), number of contacts (single
contact and multi contact switches), number of
poles and throws (SPST, DPDT, SPDT, etc.),
operation and construction (push button,
toggle, rotary, joystick, etc.), based on state
(momentary and locked switches), etc.

4. SINGLE POLE
SINGLE THROW
SWITCH (SPST)
The pole represents the number of
individual power circuits that can be
switched.
The number of throws represents the
number of states to which current can
pass through the switch.
This is the basic ON and OFF switch
consisting of one input contact and
one output contact.
It switches a single circuit and it can
either make (ON) or break (OFF) the
load.
The contacts of SPST can be either
normally open or normally closed
configurations

5. SINGLE POLE
DOUBLE THROW
SWITCH (SPDT)
This switch has three terminals,
one is input contact and
remaining two are output
contacts.
This means it consist two ON
positions and one OFF position.
In most of the circuits, these
switches are used as changeover
to connect the input between two
choices of outputs.
The contact which is connected to
the input by default is referred as
normally closed contact and
contact which will be connected
during ON operation is a normally
open contact.

6. DOUBLE POLE
SINGLE THROW
SWITCH (DPST)
This switch consists of four terminals,
two input contacts and two output
contacts.
It behaves like a two separate SPST
configurations, operating at the same
time.
It has only one ON position, but it can
actuate the two contacts
simultaneously, such that each input
contact will be connected to its
corresponding output contact.
In OFF position both switches are at
open state.
This type of switches is used for
controlling two different circuits at a
time.
Also, the contacts of this switch may

7. DOUBLE POLE
DOUBLE THROW
SWITCH (DPDT)
This switch consists of six terminals;
two input terminals (pole) and two
terminals for each pole, so total four
output terminal (throw) as shown in
figure-4a. Operation of this switch is
similar to the two separate SPDT
switches operate at a same time. In
this switch, two terminal of input
(pole) are connected with one set
(two) of output (throw-1) in position-
1 of switch. If we change the position
of switch, it will connect this input
with second set of output (terminal-2)
as shown in figure-4b. Here as shown
in example, let us assume that, in
position-1 if motor is rotating in
clockwise direction, if we change to
position-2 motor will rotate in anti-

8. PUSH
BUTT
ON
SWITC
H
When you press the switch, contacts of switch is
closed and make circuit close to flow the current
and when you remove pressure from the button,
contacts of switch is open and break the circuit.
So, this switch is momentary contact switch which
is able to control the circuit by making and
breaking its contact. In push button switch, when
you remove pressure from the switch, there is an
arrangement of spring to open contact.

9. TOGGLE
SWITCH
This type of switch is
commonly used in
household application to
ON and OFF electrical
appliances. It has a lever
by which we can move up
or down to ON and OFF
appliances.