This project creates an energy-saving HVAC control system that automatically adjusts temperature settings based on room occupancy. When a room is occupied, the system maintains normal temperature; when the room is empty for a set period, it enters an energy-saving mode with a temperature setback. This can reduce heating and cooling costs by 10-20% annually.<\/p>\n
Difficulty:<\/strong> Intermediate PIR sensors placed in key rooms detect occupancy. When no motion is detected for a set period (e.g., 30 minutes), the system sends a signal to the HVAC system to adjust the temperature setpoint (higher for cooling, lower for heating). When occupancy is detected again, the system returns to the normal setpoint. Multiple sensors can be networked for whole-home occupancy tracking.<\/p>\n This project assumes you have a smart thermostat with API access (Nest, Ecobee) or an HVAC system with remote control capability.<\/p>\n This project can integrate with various smart thermostats:<\/p>\n This tutorial uses Home Assistant as the central controller for simplicity.<\/p>\n Create the following automations in Home Assistant:<\/p>\n If you don’t have Home Assistant, you can use an ESP32 to control a relay that directly interfaces with a simple thermostat:<\/p>\n For whole-house control, create a template sensor that aggregates all PIR sensors:<\/p>\n According to DOE, setting thermostats back 7-10\u00b0F for 8 hours per day can save 10% on heating and cooling costs. This system can achieve similar savings by automatically managing setbacks based on actual occupancy.<\/p>\n This occupancy-based HVAC control system automatically reduces energy waste when rooms are empty, lowering utility bills without sacrificing comfort. With proper installation, it can pay for itself within one heating or cooling season.<\/p>\n","protected":false},"excerpt":{"rendered":" Project Overview This project creates an energy-saving HVAC control system that automatically adjusts temperature settings based on room occupancy. When a room is occupied, the system maintains normal temperature; when the room is empty for a set period, it enters an energy-saving mode with a temperature setback. This can reduce heating and cooling costs by […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[],"class_list":["post-3916","post","type-post","status-publish","format-standard","hentry","category-projects"],"blocksy_meta":[],"yoast_head":"\r\n
\nEstimated time:<\/strong> 3-4 hours
\nEstimated cost:<\/strong> $30-50<\/p>\nHow It Works<\/h2>\n
Materials Needed<\/h2>\n
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Thermostat Compatibility<\/h2>\n
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Home Assistant Setup<\/h2>\n
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ESPHome Configuration for PIR Sensors<\/h2>\n
# ESPHome configuration for multiple PIR sensors\nesphome:\n name: occupancy_sensors\n\nesp32:\n board: esp32dev\n\n# Wi-Fi configuration\nwifi:\n ssid: \"YourWiFiSSID\"\n password: \"YourWiFiPassword\"\n fast_connect: true\n\n# API for Home Assistant\napi:\n password: \"YourAPIPassword\"\n\nota:\n password: \"YourOTAPassword\"\n\n# Binary sensors for each PIR\nbinary_sensor:\n - platform: gpio\n pin: GPIO4\n name: \"Living Room Motion\"\n device_class: motion\n filters:\n - delayed_on: 100ms\n - delayed_off: 60000ms # Stay on for 1 minute after last motion\n \n - platform: gpio\n pin: GPIO5\n name: \"Bedroom Motion\"\n device_class: motion\n filters:\n - delayed_on: 100ms\n - delayed_off: 60000ms\n \n - platform: gpio\n pin: GPIO6\n name: \"Kitchen Motion\"\n device_class: motion\n filters:\n - delayed_on: 100ms\n - delayed_off: 60000ms\n<\/code><\/pre>\nHome Assistant Automations<\/h2>\n
Automation 1: Enter Away Mode When No Motion<\/h3>\n
# configuration.yaml or via UI\nautomation:\n - alias: \"HVAC - Enter Away Mode\"\n trigger:\n - platform: state\n entity_id: \n - binary_sensor.living_room_motion\n - binary_sensor.bedroom_motion\n - binary_sensor.kitchen_motion\n to: \"off\"\n for: \"00:30:00\" # 30 minutes of no motion\n condition:\n - condition: state\n entity_id: binary_sensor.house_occupied\n state: \"on\"\n action:\n - service: climate.set_temperature\n target:\n entity_id: climate.main_thermostat\n data:\n temperature: 62 # Heating setback\n hvac_mode: heat\n - service: input_boolean.turn_off\n target:\n entity_id: input_boolean.house_occupied\n<\/code><\/pre>\nAutomation 2: Return to Normal Mode When Motion Detected<\/h3>\n
automation:\n - alias: \"HVAC - Return to Normal\"\n trigger:\n - platform: state\n entity_id: \n - binary_sensor.living_room_motion\n - binary_sensor.bedroom_motion\n - binary_sensor.kitchen_motion\n to: \"on\"\n condition:\n - condition: state\n entity_id: binary_sensor.house_occupied\n state: \"off\"\n action:\n - service: climate.set_temperature\n target:\n entity_id: climate.main_thermostat\n data:\n temperature: 68 # Normal heating temperature\n - service: input_boolean.turn_on\n target:\n entity_id: input_boolean.house_occupied\n<\/code><\/pre>\nInput Boolean for Occupancy Status<\/h3>\n
input_boolean:\n house_occupied:\n name: House Occupied\n initial: true\n icon: mdi:home\n<\/code><\/pre>\nArduino Code (Standalone Version without Home Assistant)<\/h2>\n
\/\/ Standalone HVAC Controller with PIR\n#include <WiFi.h>\n\nconst int pirPin = 4;\nconst int relayPin = 5; \/\/ Controls setback circuit\n\n\/\/ Wi-Fi for logging (optional)\nconst char* ssid = \"YourWiFiSSID\";\nconst char* password = \"YourWiFiPassword\";\n\nunsigned long lastMotionTime = 0;\nconst unsigned long setbackDelay = 1800000; \/\/ 30 minutes\nbool inSetback = false;\n\nvoid setup() {\n Serial.begin(115200);\n pinMode(pirPin, INPUT);\n pinMode(relayPin, OUTPUT);\n digitalWrite(relayPin, LOW); \/\/ Normal mode (relay off)\n \n WiFi.begin(ssid, password);\n delay(60000); \/\/ PIR warm-up\n}\n\nvoid loop() {\n bool motion = digitalRead(pirPin) == HIGH;\n \n if (motion) {\n lastMotionTime = millis();\n if (inSetback) {\n \/\/ Return to normal mode\n digitalWrite(relayPin, LOW);\n inSetback = false;\n Serial.println(\"Motion detected - returning to normal mode\");\n }\n }\n \n if (!inSetback && (millis() - lastMotionTime > setbackDelay)) {\n \/\/ Enter setback mode\n digitalWrite(relayPin, HIGH);\n inSetback = true;\n Serial.println(\"No motion - entering setback mode\");\n }\n \n delay(100);\n}\n<\/code><\/pre>\nMultiple Room Occupancy Tracking<\/h2>\n
# template.yaml\ntemplate:\n - binary_sensor:\n - name: \"Any Motion\"\n state: >\n {{ is_state('binary_sensor.living_room_motion', 'on') or\n is_state('binary_sensor.bedroom_motion', 'on') or\n is_state('binary_sensor.kitchen_motion', 'on') }}\n delay_off:\n minutes: 30\n<\/code><\/pre>\nInstallation Steps<\/h2>\n
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Energy Savings Calculation<\/h2>\n
Project Extensions<\/h2>\n
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Troubleshooting<\/h2>\n
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Conclusion<\/h2>\n