Internet of Things

An IoT system has four layers: the device (sensor and small computer), the connection, a platform that stores and routes data, and an application people use.

• Sensors measure (temperature, light, motion). Actuators act (a relay, a motor, a light).
• The connection carries data to a platform. The platform stores, checks and forwards it.
• The application shows charts or sends alerts.
• A fault in any layer looks like missing data. Learn to test each layer on its own.

Activity. Draw the four layers for one product you know and name one failure at each layer.

Standard to meet. Name all four layers with correct jobs, and describe four distinct failures.

A sensor changes a physical quantity into an electrical signal. The board reads the signal and converts it to a number with a unit.

• Always keep the unit with the number: 4.2 C, not 4.2.
• Calibrate against a trusted reference. A glass of ice water should read close to 0 C.
• Sampling: how often you read. More readings cost more power.
• Reject impossible values (for example minus 100 C) before storing them.

Activity. Calibrate your sensor against ice water and a second reference and record the offsets.

Standard to meet. Record offsets with date and method, and filter out impossible values.

No connection is best everywhere. Choose by range, power, data amount and cost.

• Wi-Fi: high speed, short range, high power. BLE (Bluetooth Low Energy): low power, short range. LoRaWAN (a long-range, low-power radio network): long range, tiny messages, very low power. Cellular: wide coverage, higher cost and power.
• Ask four questions: how far, how often, how much data, what power source.
• Check local radio rules for each technology in your place.
• Write a one-line reason for the choice.

Activity. Fill a comparison table for three real cases and justify each choice.

Standard to meet. Answer the four questions for every choice, and check the local rules.

Battery life depends on how long the device is awake. A short wake with a long sleep stretches the battery.

• Average current = (active current x active time + sleep current x sleep time) / total time.
• Example: active 80 mA for 2 s every 600 s, sleep 10 microamps (0.01 mA). Active share = 80 x 2 / 600 = 0.267 mA; sleep adds about 0.01 mA; average about 0.277 mA.
• A 2000 mAh battery gives 2000 mAh / 0.277 mA = about 7,220 hours, roughly 300 days, before reductions for cold, ageing and self-discharge (slow loss of charge when idle).
• Apply a safety factor of 0.7 and state it.

Activity. Calculate your device's battery life at three sampling intervals and compare.

Standard to meet. Show the formula, use correct units, state the factor, and present three results in a table.

Devices send small structured messages. JSON is a simple text format; MQTT is a lightweight way to publish messages to a topic.

• A message: {"device":"cold-01","t":4.2,"unit":"C","time":"2026-11-02T09:00:00Z"}.
• Publish to a topic such as site/coldroom/temp. Subscribers get every message.
• Keep messages small and include a time and a device id.
• If the connection drops, store readings and send them later in order.

Activity. Publish ten readings to a test topic and confirm each one arrives with a time.

Standard to meet. Receive ten messages, check that the times are correct, and pass one outage test.

Connected devices are often attacked through default passwords and old software. Good habits are cheap.

• Change every default password. Never share one password across devices.
• Encrypt traffic and keep a list of devices with their software version.
• Update on a schedule; remove devices you no longer use.
• Give each device only the access it needs.

Activity. Audit your own build against the four habits and fix what fails.

Standard to meet. Remove every default or shared password, and date the version list.

Bring the pieces together: sensor, calibration, sleep cycle, message, storage and chart.

• Wire only at 5 V or below and check polarity before power.
• Test on the bench for one day before leaving it for seven.
• Keep a build log: change, reason, result.
• Export the data to a spreadsheet and chart it.

Activity. Run the logger for seven days and produce the chart and report.

Standard to meet. Check that fewer than 2 percent are missing, label the chart with units, and complete the build log.

The last step is judging your own design honestly and writing a report another person can act on.

• State what worked, what failed, what you would change.
• Show the battery calculation and the data quality figure.
• List risks you did not cover.
• Ask two peers to rate the report with the rubric.

Activity. Write a two-page report and present it for five minutes.

Standard to meet. Trace all numbers, and have two peers rate it Meets or better.

On the slide: L1 Basic · What IoT means

Notes: Name the four layers of an IoT system. Notes: device, connectivity, platform and application; learners match each to a smart-home example.

On the slide: L2 Awareness · Sensors and safety

Notes: Tell a sensor from an actuator and keep to 5 V or below with no mains. Notes: check the voltage rule before any wiring and record it.

On the slide: L3 Foundation · Send a reading

Notes: Send a sensor reading as a message with a time and device ID. Notes: use a topic name that makes sense; learners check that readings can be ordered and traced.

On the slide: L4 Practitioner · Build the temperature logger

Notes: Build a logger, filter impossible values and test its accuracy. Notes: compare with a reference thermometer at two points and record the error.

On the slide: L5 Specialist · Power and security

Notes: Estimate battery life with a safety factor and set strong device passwords. Notes: average current is the sum of active and sleep current-times divided by total time; apply a safety factor for cold and ageing.

On the slide: L6 Advanced · Lead a deployment

Notes: Plan the install of several devices with a naming plan, test and maintenance round. Notes: sample three devices for data quality and security.

On the slide: L7 Super expert · Design an IoT system

Notes: Design a system with connectivity choice, power budget, security and data plan. Notes: justify LoRaWAN or another link by range, message size and power; present risks and a review schedule.