IOT Architecture

Components

• Uniquely identifiable embedded system connected with the internet infrastrcuture
• IOT Devices collect data through sensors
• The data is sent to the internet through the gateway
• Things and Gateway are generally considered as the edge of the internet
• Data analytics takes place in the cloud
• Following anayltics actuator commands might be sent

Why do anayltics on the IOT device rather than the cloud

• Security
• Time
• Cost

• Sensor reads in analog data that is converted to digital forms using analog to digital converter
• Actuator receives digital signal that is converted to electrical or electromechnical signals through DAC
• Controller contains a processor
• Controller is connected to the internet

Example

• 10 sensors

Sensor

• Connect the analog world to digital
• Each IOT sensor collects a stream of time correlated data that must be transmitted securely, possibly anaylsed and possibly stored
• Value of IOT is in the data in aggregate from multiple sensors
• Sensor data may not be always be reliable and sensors can fail in field

Digital input

• Example: On off Switches
• Push button: Reverse for normally closed switch
• Push on switch: Must be depressed again too release

Contact bounch of mechanical switch

• Contact bounce: Mechanical switches do not make clean transition between on off position, makes/break contact multiple times for tens of millisecons
• Microcontroller is fast and can recognised each swithc bound
• Debouncing solution:
  • Hardware debounce circuit
  • Software technique: Insert delay

Analog sensors

• Converts the analog data to digital
• Examples
  • Temperature sensor uses the fact that as the temp increases, the voltage across a diode chantges at known rate
  • Flex sensor provides a change in resistance for a change in sensor flexture

Continous time signal

• A continuous time signal is defined over all instance of time
• A function of time (The real number) to the co-domain X

Discrete signal

• Sequence or series of signal values defined in discrete points of time
• THe distance in time between each point of time is the time step

Digital Signal: Quantisation

• Digital signal is a discrete signal for which not only the time but also the amplitude has been made discrete
• ADC samples and quantizes an analog signal to digital signal

ADC (Quantization and encoding)

• Input boltages are typically mapped in range of 0-5 volts
• b bit allows to divide the input signal range into 2^b different quantization level
• The more bits we have available, the higher resolution: (volatage span)/2^b = (vref (hih) - Vref(low))/2^b

Output devices and actuators

• Digital Output
  • Example: LED
  • Informs the presence of logic 0 or logic 1 at a specific pin of a microcontroller
• Analog actuators

Pulse width modulation (PWM)

• Method to create an analoig signal from a digital processor
• The main idea is to keep the signal high for an amt of time proportianl to the aplitude of the required analog sigals

Example

• During the period, the pulses are on for a certain period of time
• What is different is how many percentage of the time is the pulse on.

Sensor/Actuators interface with microcontoller

• Sensor data has to be processed and transmitted
• Sensor connect to a microcontller through established I/O interfaces and communication system
• Video system need much faster I/0 such as MIPI, USB, UCB expresee

I2C communcation protocol

• Reqyures 2 wires
• Serial interace
• Sending one bit at a time
• Use for short distance communication

Sensor

• Ambient light sensor
• Infrared Tempt sensor
• Humidity and temperature sensor
• Barametric pressure sensor
• Motion sensor
• 3D accelerometer and gyroscope
• Bungee Jump Acceleration

Summary

• IOT device consist of sensor actuators and microcontroller
• Variery of sensor connect to the cyber world to the physical world
• ADC And DAC perform transformation between analog and digital

Slides