Smart Fan Controller with Temperature and Occupancy Sensing

Fans are left running in empty rooms all day — wasted electricity and wasted motor life. The fix is a controller that knows two things: how hot the room is, and whether anyone is in it. This project builds that controller: a DHT22 temperature/humidity sensor and a PIR motion sensor feed an ESP32, which drives a fan through a relay plus speed-control stage. The logic is straightforward and demonstrable: no motion for a configurable timeout switches the fan off; on occupancy, fan speed steps up with temperature across three bands. The 16x2 LCD shows temperature, humidity, motion state and fan speed at all times, and push buttons allow manual speed override. A cloud dashboard logs temperature and fan state so the energy-saving behavior is visible as data, not just claimed.

1. The DHT22 is sampled every few seconds for temperature and humidity; the PIR sensor reports motion events.
2. If no motion has been detected for the timeout period, the ESP32 switches the fan off and the LCD shows "NO OCCUPANCY".
3. On motion, the controller reads the temperature and selects the speed band: below the low threshold the fan stays off, between thresholds low/medium, above the high threshold full speed.
4. Hysteresis bands prevent rapid switching when the temperature hovers at a boundary.
5. The LCD updates with temperature, humidity, motion state and fan speed; manual buttons can override at any time.
6. Every state change and periodic readings publish over Wi-Fi to the cloud dashboard for the occupancy and temperature history.

Tech stack:

• ESP32 development board (Wi-Fi)
• Arduino IDE (C/C++ firmware)
• DHT22 temperature/humidity sensor (±0.5 °C datasheet)
• PIR motion sensor module (HC-SR501 class)
• Relay module + speed-control stage for the demo fan
• 16x2 LCD with I2C backpack
• Push buttons for manual override
• Cloud dashboard (ThingSpeak/Blynk class) over MQTT/HTTP
• Model fan + 5 V/12 V supplies

• [Temperature-based speed] The DHT22 (±0.5 °C datasheet) feeds a three-band speed map — low, medium, high — with hysteresis so the fan does not hunt between speeds at the boundary.
• [Occupancy auto-off] The PIR motion sensor watches the room; if no motion is seen for the configurable timeout (default approximately 5 minutes), the fan switches off automatically.
• [Speed-control stage] A relay plus PWM/triac-style speed stage drives the demo fan at the selected speed band; the wiring guide documents the stage for the demo motor.
• [Live LCD status] The 16x2 LCD continuously shows temperature, humidity, motion state and current fan speed — the whole control loop is visible.
• [Manual override] Push buttons set the speed manually or force the fan off; automatic control resumes on the next occupancy/temperature change.
• [Cloud logging] Temperature, humidity, occupancy and fan state publish over Wi-Fi to a dashboard, producing a visible record of the auto-off energy saving.
• [Hysteresis design] Speed-band switching uses separate up/down thresholds so the fan never oscillates — the report documents the hysteresis values.

• Working prototype: ESP32, DHT22, PIR sensor, relay + speed stage, model fan, LCD, buttons
• Complete ESP32 firmware (sensor reading, occupancy timeout, hysteresis speed logic, LCD, cloud publishing)
• Speed-band and hysteresis configuration guide
• Cloud dashboard setup guide
• Wiring diagram and connection table
• Project report PDF (background, control logic, methodology, working, results)
• PPT presentation for final review
• Viva Q&A preparation document (DHT22/PIR interfacing, hysteresis, relay driving, IoT logging)

• The demo uses a low-voltage model fan; switching a real 230 V ceiling fan needs a properly rated isolation stage and is electrical-installation work outside the project scope.
• PIR sensors detect motion, not presence — a perfectly still person can time out; the report documents this honestly and the timeout is configurable.
• The DHT22's ±0.5 °C is a datasheet figure; band thresholds should be set with that tolerance in mind.
• Speed control on the demo fan is stepped (3 bands), not continuously variable.
• The dashboard needs Wi-Fi; the controller and LCD work locally without it.