The Engorio IoT Encyclopedia
From your first blinking LED to connected, intelligent systems
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How to use this book
This book takes you from zero electronics knowledge to designing complete, connected IoT systems. Tech and postgraduate students, and for makers building their first product.
What is IoT
The Internet of Things (IoT) is a network of physical devices that sense the world, make decisions and act, while exchanging data over a network.
Electronics fundamentals
Three quantities explain almost every circuit you will build: voltage pushes, current flows, and resistance opposes. Master Ohm's law and the LED resistor calculation, and most beginner mistakes disappear.
Digital and analog signals
A microcontroller understands only two things: digital levels (HIGH or LOW) and analog voltages converted into numbers. Knowing the voltage limits of each pin is what keeps your boards alive.
Tools and workbench
A breadboard, jumper wires, a multimeter and a good USB cable are enough to build 80% of student IoT projects. Add a soldering iron when you are ready to make projects permanent.
Microcontroller basics
A microcontroller (MCU) is a complete small computer on one chip: processor, memory and input/output pins.
The Arduino family
Arduino boards are the easiest way to start: 5 V tolerant, nearly indestructible, and backed by thousands of libraries and tutorials. For a first project without WiFi, an Uno or Nano is still the best choice.
ESP8266 and ESP32 family
Espressif's ESP32 is the default chip for student IoT: built-in WiFi and Bluetooth, a fast dual-core processor and a price close to an Arduino clone. Learn its pin traps once and it will power most of your projects.
Raspberry Pi and single-board computers
A single-board computer (SBC) runs a full Linux operating system, so it can handle cameras, databases, web servers and AI models that a microcontroller cannot.
Other microcontrollers and choosing a board
For almost every student project the answer is an ESP32, an Arduino Uno/Nano or a Raspberry Pi.
Sensor fundamentals
A sensor converts a physical quantity, such as heat, light, distance or gas, into an electrical signal your board can read. Before you choose one, know its output type, range, accuracy and supply voltage.
Environmental sensors
Environmental sensors measure the air, water, soil and light around a device. For most projects, a DHT22 or BME280 covers climate, an MQ sensor gives a gas alarm, and a capacitive probe handles soil moisture.
Motion, distance and position sensors
These sensors tell a device whether something moved, how far away it is, which way it is tilted and where on Earth it stands.
Human, biometric and input sensors
These sensors identify people, read their body signals and take their commands. They power the most popular student projects: RFID attendance, fingerprint locks, health monitors and voice or gesture control.
Electrical and industrial sensors
These sensors measure electricity, fluids and safety hazards. They are the core of Electrical, Mechanical, Civil and Fire Safety projects: energy meters, water-flow monitors, tank controllers and fire alarms.
Motors and motion control
Motors turn your IoT decisions into movement: wheels, valves, doors, conveyors and robot arms. Never connect a motor directly to a GPIO pin; always use a driver and a separate power supply with a shared ground.
Relays and power switching
3 or 5 V, but your loads may need amps at 12 V or 230 V. Switching devices bridge that gap: transistors and MOSFETs for DC loads, relays and SSRs for AC appliances.
Displays, lights and sound
96-inch OLED for readings, a 16×2 LCD for menus, LEDs for alerts and a buzzer for alarms. Most popular displays need only four wires over I2C.
Wired communication protocols
Modules talk to your board over a handful of standard buses.
Wireless technologies
The right radio depends on three things: range, data rate and battery life.
IoT application protocols
Once a device is on a network, it needs a common language to exchange data with servers and apps.
Programming for IoT
Good IoT firmware never freezes: it reads sensors, handles the network and responds to commands at the same time.
Cloud platforms, apps and dashboards
The cloud stores your data, runs rules and lets you control devices from anywhere.
Data, edge computing and AI on the edge
Collecting data is only half the job; value comes from storing it well, showing it clearly and acting on patterns.
Power supplies and batteries
Most IoT failures are power failures: brownouts, noisy motors, dead batteries. Size your supply for the peak current, give motors their own supply, and for battery devices calculate the average current before you build.
From breadboard to product
A breadboard proves an idea; a soldered board or PCB in a proper enclosure survives a demo, a viva and real use. Move to a permanent build once the circuit and code work end to end.
IoT security
An insecure IoT device is a door into someone's home, hospital or factory. Most attacks exploit simple mistakes: default passwords, unencrypted traffic and secrets left in code.
Debugging and troubleshooting
Most IoT bugs are found in this order: power, wiring, configuration, then code. Check them in that sequence, change one thing at a time, and test each part alone before blaming the whole system.
Planning, documenting and presenting a project
Examiners grade three things: does it work, do you understand it, and is it documented properly.
Quick reference and glossary
Keep this chapter open on your bench. It collects the formulas, I2C addresses and terms you will need again and again; pin maps for the Uno, NodeMCU, ESP32 and Raspberry Pi are in Chapters 6, 7 and 8.
Sources
Facts about recently released boards and chips were checked against these pages; everything else reflects established electronics and IoT practice.