This documents is useful for an embedded engineer who is advancing in Internet of things.

1. By
Santhi Kumaran
ACEIoT

2. Types of Signals
Analog:
An analog signal is a continuous signal and is often represented
by a V(t).
A dimmer light switch continuously increases/decreases the
current.
Digital :
A digital signal is a discrete time signal, binary signal.
An On/Off light switch applies a fixed, predetermined voltage.

3. Analog and Digital Signals
Light intensity
Temperature
Pressure

4. Analog-to-Digital Conversion
Sampling – converts the continuous signal into a series of discrete
analog signals at periodic intervals
Quantization – each discrete analog is converted into one of a finite
number of (previously defined) discrete amplitude levels
Encoding – discrete amplitude levels are converted into digital code
Variable
Time
Analogue Signal
1001 1101 0101
Discrete
Variables

5. Features of an ADC
Sampling rate – rate at which continuous analog signal
is polled e.g. 1000 samples/sec
Quantization – divide analog signal into discrete levels
Resolution – depends on number of quantization levels
Conversion time – how long it takes to convert the
sampled signal to digital code
Conversion method – means by which analog signal is
encoded into digital equivalent
 Example – Successive approximation method

6. Sensors and Actuators
Sensor (e.g., thermometer)
 a device that detects/measures a signal or stimulus
 acquires information from the “real world”
Actuator (e.g., heater)
 a device that generates a signal or stimulus
real
world
sensor
actuator
intelligent
feedback
system
sensor
input
signal
(measurand)
microcontroller
signal processing
communication
sensor data
analog/digital
network
display
Typical Electronic Sensor System

7. Analog Sensors
 Sensors that produce continuous analog output signal and these
sensors are considered as analog sensors.
 This continuous output signal produced by the analog sensors is
proportional to the measurand.
 Practical examples of various types of analog sensors are as
follows: accelerometers, pressure sensors, light sensors, sound
sensors, temperature sensors, and so on.

8. Accelerometers
Analog sensors that detect changes in position, velocity, orientation,
shock, vibration, and tilt by sensing motion are called as
accelerometers.
These accelerometers are available as analog and digital sensors, based
on the output signal. Analog accelerometer produces a constant variable
voltage based on the amount of acceleration applied to the accelerometer.

9. Light sensor
Analog sensors that are used for detecting the amount of light striking
the sensors are called as light sensors. These analog light sensors are
again classified into various types such as photo-resistor, Cadmium
Sulfide (CdS), and, photocell.

10. Sound Sensor
Analog sensors that are used to sense sound level are called as sound
sensors. These analog sound sensors translate the amplitude of the
acoustic volume of the sound into an electrical voltage for sensing sound
level. This process requires some circuitry, and utilizes microcontroller
along with a microphone for creating an analog output signal.

11. Pressure Sensor
The analog sensors that are used to measure the amount of pressure
applied to a sensor are called as analog pressure sensors. Pressure
sensor will produce an analog output signal that is proportional to the
amount of applied pressure. These piezoelectric sensors are used for the
generation of electric charge.

12. Analog Temperature sensor
Temperature sensors are widely available as both digital and analog
sensors. Typically used analog temperature sensors are thermistors.
Thermistor is a thermally sensitive resistor that is used for detecting
changes in temperature. If the temperature increases, then the electrical
resistance of thermistor increases. Similarly, if temperature decreases,
then the resistance decreases.

13. Ultrasonic sensors
The high frequency sound waves generated by active ultrasonic
sensors are received back by the ultrasonic sensor for evaluating the
echo. Thus, the time interval taken for transmitting and receiving the
echo is used for determining the distance to an object. But, passive
ultrasonic sensors are just used for detecting ultrasonic noise which is
present under specific conditions.

14. Digital Sensors
Electronic sensors or electrochemical sensors in which data conversion
and data transmission takes place digitally are called as digital sensors.
These digital sensors are replacing analog sensors as they are capable
of overcoming the drawbacks of analog sensors. In digital sensors, the
signal measured is directly converted into digital signal output inside the
digital sensor itself.

15. Digital Sensors
Button
Motion
Bumper Switch Sensor
Lever
Limit Switch Sensor
Ultrasonic sensor

16. Digital Temperature Sensor
DS1620 is a digital temperature sensor that provides temperature of device
with 9-bit temperature readings. It acts a thermostat with its three thermal
alarm outputs. If the temperature of device is greater than or equal to user
defined temperature TH, then THIGH is driven high. If the temperature of
the device is less than or equal to user defined temperature TL, then the
TLOW is driven high. If the temperature of the device exceeds TH and
remains high until it falls below that of TL, then the TCOM is driven high.

17. Digital Accelerometers
The method of generation of variable frequency square wave output by
the digital accelerometer is called as pulse-width modulation. The output
PWM signal, pulse width or duty cycle is proportional to the acceleration
value.

18. Sensors for a
Robot
Touch sensors tell the robot
when it bumps into
something.
Light sensors measure light
intensity.
gyroscopes tell the robot which
direction is up.
Heat Sensors which measure
temperature.
Ultra Sonic Rangers tell the robot
how far away objects are.
1. Resistive
2. Infra-red
3. Light
4. Sonar
5. Other

19. Other Sensors
RFID
Barcode
Proximity
Vision
Gyroscope
Compass
Tilt/Acceleration
Etc.

21. Actuators
Hardware devices that convert a controller command
signal into a change in a physical parameter
The change is usually mechanical (e.g., position or
velocity)
An actuator is also a transducer because it changes
one type of physical quantity into some alternative
form
An actuator is usually activated by a low-level
command signal, so an amplifier may be required to
provide sufficient power to drive the actuator

22. THANKYOU