Sensors and Actuators

Sensors and Actuators

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
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

4. 2. Actuator:
•Anactuatorisaformoftransducerdevice
(mechanicalorelectrical)whichconvertssignalsto
correspondingphysicalaction.
•Actuatoractsasanoutputdevice.
–E.g.:Steppermotor
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

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.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

6. a)Light Emitting Diode (LED):
•LightEmittingDiode(LED)isanimportantoutputdeviceforvisual
indicationinanyembeddedsystem.
•LEDcanbeusedasanindicatorforthestatusofvarious
signalsorsituations.
•LightEmittingDiodeisap-njunctiondiodeanditcontainsananode
andacathode.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

7. LEDs can be interfaced to the port pin of a processor/controller in two
ways:
–Inthefirstmethod,theanodeisdirectlyconnectedtotheportpin
andtheportpindrivestheLED.Cathodeisgrounded.Itiscalled
commoncathodemethod.
–Inthesecondmethod,thecathodeoftheLEDisconnectedtothe
portpinoftheprocessor/controllerandtheanodetothesupply
voltagethroughacurrentlimitingresistor.Itiscalledcommon
anodemethod.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

8. b)7-segment LED display:
•The7-segmentLEDdisplayisanoutputdevicefordisplayingalphanumeric
characters.
•7LEDsegmentsusedfordisplayingalphanumericcharactersand1LEDused
forrepresenting'decimalpoint'indecimalnumberdisplay.
•TheLEDsegmentsarenamedAtoGandthedecimalpointLEDsegmentis
namedasDP.
•TheLEDsegmentsAtoGandDPshouldbelitaccordinglytodisplaynumbers
andcharacters.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

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.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

10. C)Stepper Motor:
•Astepper motoris an electromechanical device which
generates discreate rotations.
•Stepper motoris widely used in industrial embedded
applications, consumer electronics, robotics etc.
•Printer/fax machines uses stepper motor for its functioning.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

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
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

12. 1.Full step mode:
Infullstepmode,boththephasesareenergized
simultaneously.Thereare4coils.Outofwhichtwoare
energized.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

13. 2.Wave step mode:
In wave step mode, only one phase is energized at a
time ad each coil is energized alternatively.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

14. 3.Half step mode:
•Half step mode is a combination of both wave step
and full step modes.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

15. d)Push Button Switch:
•Itisaninputdevice.
•Itcomesintwoconfigurations,namely'PushtoMake'and'Pushto
Break’.
–Inthe'PushtoMake'configuration,theswitchisnormallyinthe
openstateanditmakesacircuitcontactwhenitispushedor
pressed.
–Inthe'PushtoBreak'configuration,theswitchisnormallyinthe
closedstateanditbreaksthecircuitcontactwhenitispushedor
pressed.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

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.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems

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.
5/15/20204 SEM -18CS44 -Microcontrollers & Embedded Systems