What is the Internet of Things?
The Internet of Things (IoT) connects ordinary objects (lamps, meters, watches, pumps, cars) to the internet so they can sense, share data and act without a person doing each step.
Features of IoT:
- Connectivity: each thing is on a network and has an address.
- Sensing: things measure the world.
- Automation: rules act by themselves.
- Remote control: you control things from far away.
- Huge data: billions of devices create big data that AI can study.
Applications: smart homes, health bands, smart farms, factories (Industry 4.0), smart cities, logistics tracking.
Parts of an IoT system: sensors, actuators, clients and servers
- Sensor: changes a physical quantity into an electrical signal (temperature, light, motion, gas, soil moisture).
- Microcontroller: a tiny computer on one chip that reads sensors and runs a program (for example Arduino-type or ESP32 boards, micro:bit).
- Actuator: does the opposite of a sensor; it turns a signal into action (motor, relay, buzzer, LED, valve).
- Gateway / router: joins the local devices to the internet.
- Server (cloud): stores data and runs rules. The device or phone app is a client that sends requests to it.
A simple project: temperature sensor → microcontroller → Wi-Fi → cloud dashboard → fan relay.
How IoT devices communicate: the three-layer model
- Perception layer: sensors and actuators touching the real world.
- Network layer: carries data. Short range: Wi-Fi, Bluetooth, Zigbee, RFID/NFC. Long range: 4G/5G mobile, LoRa, NB-IoT. Data is sent in small packets using protocols such as MQTT or HTTP.
- Application layer: cloud services and apps that store, show and act on data.
A smart home often has a hub that talks Zigbee or Bluetooth to small sensors and Wi-Fi to the router. Some decisions are made in the cloud; some are made on the device itself (edge computing) for speed.
Benefits, problems, privacy and security
Benefits: saves energy and water, early warnings (gas leak, fall alarm), less manual work, new services such as pay-per-use.
Problems: devices with weak default passwords can be hacked; cameras and speakers can leak private life; devices stop working without internet; e-waste.
Protection:
- Technical: encryption (data locked so only the receiver can read it), firewalls, software updates, sandboxes that keep apps apart.
- Organisational: strong unique passwords, give each app only the data it needs, read privacy settings.
- Physical: keep hubs and routers where strangers cannot reach them.
Try it: design a smart-home system
On paper, design a “smart plant pot”. List: the sensor (soil moisture), the actuator (small pump), the rule (if moisture < 30% water for 5 s), the network (Wi-Fi), the app screen, and one security step. If you have a micro:bit or similar board, build it with a cup of soil. In the 3D, raise the temperature above the limit and watch the fan switch on.
Key formulas and definitions
- IoT loop: Sense → Send → Decide → Act
- Sensor: physical change → data; Actuator: data → physical action
- Three layers: Perception · Network · Application
- Short range: Wi-Fi, Bluetooth, Zigbee, NFC; long range: 4G/5G, LoRa, NB-IoT
- Rule form: IF condition THEN action (e.g. IF T > 28 °C THEN fan ON)
- Security: encryption + strong passwords + updates + firewall
Worked examples
1. Name the sensor and actuator in an automatic street light.
Sensor: light sensor (LDR) measures daylight. Actuator: relay that switches the lamp on when it gets dark.
2. A smart bin sends its fill level every 30 minutes. How many messages does it send in a day?
24 h × 2 per hour = 48 messages per day.
3. Write the rule and list the layers for a smart irrigation system.
Rule: IF soil moisture < 30% AND no rain forecast THEN open valve for 10 minutes. Perception: moisture sensor + valve. Network: LoRa or 4G to the cloud. Application: farmer's phone app showing moisture and a manual button.
4. A family's smart camera still uses the password “admin”. What could go wrong and how do you fix it?
Attackers who scan the internet for default passwords can watch the video. Fix: set a strong unique password, update the firmware, turn on encryption and two-step login.
Common mistakes
- Mixing up sensors and actuators: a sensor measures, an actuator moves or switches.
- Thinking IoT means only Wi-Fi. Many devices use Bluetooth, Zigbee, LoRa or mobile networks.
- Thinking a device is safe because it is small. Weak passwords on cameras and plugs are a common attack route.
- Forgetting that a rule needs data first: no sensor reading, no decision.