This document discusses different sensors, actuators, and input/output subsystems used in embedded systems. It describes LEDs, 7-segment displays, stepper motors, push button switches, and keyboards. It provides details on how each component interacts with a microcontroller, their configurations, and operating principles. Sensors receive input from the external environment. Actuators such as stepper motors are output devices that convert signals into physical actions.

1. SENSORS, ACTUATORS &
I/O SUB SYSTEMS
4 SEM - 18CS44 - Microcontrollers & Embedded Systems 5/15/2020

2. Contents:
– LEDs
– 7-Segmet displays
– Stepper motor
– Push button switch
– Keyboard
4 SEM - 18CS44 - Microcontrollers & Embedded
Systems
5/15/2020
1. Sensors
2. Actuators
3. I/O Sub systems

3. 1.Sensor:
• A sensor is a transducer device that converts energy
from one form to another.
• E.g.: Temperature sensor, magnetic Hall Effect sensor,
humidity sensor, etc
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4. 2. Actuator:
• An actuator is a form of transducer device
(mechanical or electrical) which converts signals to
corresponding physical action.
• Actuator acts as an output device.
– E.g.: Stepper motor
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5. 3. I/O Sub systems:
• The interaction happens through the sensors and actuators
connected to the input and output ports of the embedded
system.
• The sensors may not be directly interfaced to the input ports,
instead they may be interfaced through some I/O subsystems.
• Few of the I/O subsystems are explained here.
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6. a)Light Emitting Diode (LED):
• Light Emitting Diode (LED) is an important output device for visual
indication in any embedded system.
• LED can be used as an indicator for the status of various
signals or situations.
• Light Emitting Diode is a p-n junction diode and it contains an anode
and a cathode.
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7. LEDs can be interfaced to the port pin of a processor/controller in two
ways:
– In the first method, the anode is directly connected to the port pin
and the port pin drives the LED. Cathode is grounded. It is called
common cathode method.
– In the second method, the cathode of the LED is connected to the
port pin of the processor/controller and the anode to the supply
voltage through a current limiting resistor. It is called common
anode method.
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8. b)7-segment LED display:
• The 7-segment LED display is an output device for displaying alpha numeric
characters.
• 7 LED segments used for displaying alpha numeric characters and 1 LED used
for representing 'decimal point' in decimal number display.
• The LED segments are named A to G and the decimal point LED segment is
named as DP.
• The LED segments A to G and DP should be lit accordingly to display numbers
and characters.
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9. The 7-segment LED displays are available in two different configurations,
namely; Common Anode and Common Cathode.
• In the common anode configuration, the anodes of the 8 segments are
connected commonly whereas in the common cathode configuration,
the cathodes of 8 LED segments are connected commonly.
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10. C)Stepper Motor:
• A stepper motor is an electromechanical device which
generates discreate rotations.
• Stepper motor is widely used in industrial embedded
applications, consumer electronics, robotics etc.
• Printer/fax machines uses stepper motor for its functioning.
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11. • Based on the coil winding arrangements, 2 phase stepper motor is
classified into 2 types
1.Uipolar
2.Bipolar
There are 3 different stepping modes in stepper motor
1.Full step
2.Wave step
3.Half step
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12. 1.Full step mode:
In full step mode, both the phases are energized
simultaneously. There are 4 coils. Out of which two are
energized.
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13. 2.Wave step mode:
In wave step mode, only one phase is energized at a
time ad each coil is energized alternatively.
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14. 3.Half step mode:
• Half step mode is a combination of both wave step
and full step modes.
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15. d)Push Button Switch:
• It is an input device.
• It comes in two configurations, namely 'Push to Make' and 'Push to
Break’.
– In the 'Push to Make' configuration, the switch is normally in the
open state and it makes a circuit contact when it is pushed or
pressed.
– In the 'Push to Break' configuration, the switch is normally in the
closed state and it breaks the circuit contact when it is pushed or
pressed.
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16. • Depending on the way in which the push button
interfaced to the controller, it can generate either a
‘HIGH’ pulse or a 'LOW' pulse.
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17. e) Keyboard:
• Keyboard is an input device for user interface.
• If the number of keys required is less, the push button switches can
be used with the port pins.
• Where more o of keys are required, then matrix keyboard is the
suitable one.
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