Monitoring my swimming pool temperature with a cheap BLE sensor and ESPHome

on home assistant, home automation, esphome, 3dprinting, diy

One accurate measurement is worth a thousand expert opinions.
– Grace Hopper

Maintaining the right temperature for my swimming pool is crucial for enjoying a good swim. Instead of frequently checking a thermometer or relying on a mobile app, I wanted to get real-time temperature updates remotely. Here’s how I achieved this using an affordable BLE sensor and ESPHome.

BLE Sensor

I found a suitable BLE sensor on AliExpress that fit my requirements perfectly:

  • Power efficiency: the sensor runs on two AAA batteries, lasting about six months.
  • Precision: it has good precision with an error of just 1° C approximately.
  • Data collecting: it works well with its dedicated mobile app, but doesn’t integrate with third-party apps.

BLE Pool Sensor

Despite its limitations, the sensor was perfect for my project. However, I needed a way to access the temperature data in real-time without using the mobile app or being near the pool.

ESPHome

To bridge this gap, I used an ESP32-WROOM-32U, which I also bought from AliExpress. The external antenna on this model ensures a reliable connection over a longer range.

ESP-WROOM-32U

The ESP32 will work just as a BLE <> Wi-Fi bridge, connecting to the sensor on each hour, reading the temperature and sending the data to Home Assistant sensors.

Here’s how I set it up on ESPHome config:

esphome:
  name: "esphome-pool-monitor"
  friendly_name: Pool Monitor

esp32:
  board: esp32dev
  framework:
    type: arduino

# Enable logging
logger:

# Enable Home Assistant API
api:
  encryption:
    key: "wmIdKCoFredactedNGeGZHeQI="

ota:

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

time:
  - platform: homeassistant
    id: homeassistant_time
    on_time:
      - seconds: 0
        minutes: 30
        then:
          - switch.turn_on: ibs_p01b_switch
          - delay: 5s
          - while:
              condition:
                and:
                  - switch.is_on: ibs_p01b_switch
                  - binary_sensor.is_off: ibs_p01b_connected
              then:
                - logger.log: "Trying connection to IBS-P01/B"
                - esp32_ble_tracker.stop_scan:
                - delay: 5s
                - esp32_ble_tracker.start_scan:
                - delay: 1min

esp32_ble_tracker:
  scan_parameters: 
    active: false
    continuous: false
    duration: 1min
  on_ble_advertise:
    - mac_address: "XX:XX:XX:XX:XX:XX"
      then:
        - lambda: |-
            ESP_LOGD("ble_adv", "IBS-P01/B device found");

button:
  - platform: template
    name: "BLE Start Scan"
    on_press:
      - esp32_ble_tracker.start_scan:
  
  - platform: template
    name: "BLE Stop Scan"
    on_press:
      - esp32_ble_tracker.stop_scan:

  - platform: restart
    name: "ESP32 Restart"

binary_sensor:
- platform: status
  name: "ESP32 Status"

- platform: template
  id: ibs_p01b_connected
  icon: mdi:bluetooth-connect
  name: "IBS-P01/B Connected"

ble_client: 
  - mac_address: XX:XX:XX:XX:XX:XX
    id: ibs_p01b
    on_connect:
      then:
        - wait_until:   
            lambda: |-
              esphome::ble_client::BLEClient* client = id(ibs_p01b);
              esphome::ble_client::BLECharacteristic* chr = client->get_characteristic(0xFFF0, 0xFFF2);

              return chr != nullptr;              
        - lambda: |- 
            ESP_LOGD("ble_client_lambda", "Connected to IBS-P01/B");
            id(ibs_p01b_connected).publish_state(true);

    on_disconnect:
      then:
        - lambda: |-
            ESP_LOGD("ble_client", "Disconnected from IBS-P01/B");
            id(ibs_p01b_connected).publish_state(false);

switch:
  - platform: ble_client
    id: ibs_p01b_switch
    ble_client_id: ibs_p01b
    name: "IBS-P01/B Enabled"
    restore_mode: ALWAYS_OFF

sensor:
  - platform: uptime
    name: "ESP32 Uptime"

  - platform: template
    device_class: timestamp
    name: "IBS-P01/B Last Measurement"
    id: "ibs_p01b_last_measurement"

  - platform: template
    name: "IBS-P01/B Temperature"
    id: ibs_p01b_temperature
    unit_of_measurement: "°C"
    accuracy_decimals: 1
    state_class: measurement
    device_class: temperature

  - platform: ble_client
    id: ibs_p01b_sensor
    type: characteristic
    ble_client_id: ibs_p01b
    service_uuid: 'fff0'
    characteristic_uuid: 'fff2'
    notify: true
    internal: true
    update_interval: 30s
    lambda: |-
      if (x.size() == 0) return NAN;

      // https://community.home-assistant.io/t/hex-string-to-dec-value/458945/2
      auto temp = (float)((int16_t)(x[1]<< 8) + x[0])/100;

      if (temp != NAN) {
        id(ibs_p01b_temperature).publish_state(temp);

        // https://community.home-assistant.io/t/publish-timestamp-into-text-sensor/122531/11
        id(ibs_p01b_last_measurement).publish_state(id(homeassistant_time).now().timestamp);

        id(ibs_p01b_switch).turn_off();
      }

      return 0.0;

Notes:

  • For obvious reasons, I redacted the mac address of my device.
  • You can find the mac address and inspect the characteristics for your sensor with apps like BT Inspector or LightBlue.
  • IBS-P01/B is the name/model of my sensor. You can use other devices for this purpose since they have bluetooth support.
  • I’ll not cover the details for setting up ESPHome and devices, but you can watch a detailed tutorial from Everything Smart Home Youtube channel.

After uploading the firmware to ESP32 and with a little luck, you will see something like that on the logs:

[16:24:04][D][switch:012]: 'IBS-P01/B Enabled' Turning ON.
[16:24:04][D][switch:055]: 'IBS-P01/B Enabled': Sending state ON
[16:24:05][D][button:010]: 'BLE Start Scan' Pressed.
[16:24:05][D][esp32_ble_tracker:266]: Starting scan...
[16:24:11][D][ble_adv:069]: IBS-P01/B device found
[16:24:11][D][esp32_ble_client:110]: [0] [XX:XX:XX:XX:XX:XX] Found device
[16:24:11][D][esp32_ble_tracker:665]: Found device XX:XX:XX:XX:XX:XX RSSI=-82
[16:24:11][D][esp32_ble_tracker:686]:   Address Type: PUBLIC
[16:24:11][D][esp32_ble_tracker:215]: Pausing scan to make connection...
[16:24:11][D][esp32_ble_tracker:303]: End of scan.
[16:24:11][I][esp32_ble_client:067]: [0] [XX:XX:XX:XX:XX:XX] 0x00 Attempting BLE connection
[16:24:24][I][ble_sensor:031]: [ibs_p01b_sensor] Connected successfully!
[16:24:26][I][esp32_ble_client:227]: [0] [XX:XX:XX:XX:XX:XX] Connected
[16:24:26][D][ble_client_lambda:115]: Connected to IBS-P01/B
[16:24:26][D][binary_sensor:036]: 'IBS-P01/B Connected': Sending state ON
[16:24:32][D][sensor:094]: 'IBS-P01/B Temperature': Sending state 22.77000 °C with 1 decimals of accuracy
[16:24:32][D][sensor:094]: 'IBS-P01/B Last Measurement': Sending state 1722626688.00000  with 1 decimals of accuracy
[16:24:32][D][sensor:094]: 'ibs_p01b_sensor': Sending state 0.00000  with 0 decimals of accuracy
[16:25:02][D][sensor:094]: 'IBS-P01/B Temperature': Sending state 22.77000 °C with 1 decimals of accuracy
[16:25:02][D][sensor:094]: 'IBS-P01/B Last Measurement': Sending state 1722626688.00000  with 1 decimals of accuracy
[16:25:02][D][sensor:094]: 'ibs_p01b_sensor': Sending state 0.00000  with 0 decimals of accuracy
[16:25:43][D][ble_client:121]: Disconnected from IBS-P01/B
[16:25:43][D][binary_sensor:036]: 'IBS-P01/B Connected': Sending state OFF
[16:25:43][W][ble_sensor:037]: [ibs_p01b_sensor] Disconnected!

And, of course, the data in Home Assistant device:

Home Assistant sensor

Wrapping Up

It’s working but it’s not finished. I need to keep the ESP32 turned on and near the pool, running continuously.

I used a standard USB 5V DC adapter plugged into a wall outlet near the pool. To protect the hardware from the elements, I 3D printed a box to accommodate both the ESP32 and the DC adapter:

ESP32 BLE Pool Monitor

If you want to print the same box for your project, download the model from my Printables profile.

This setup has been running flawlessly for the past 10 months, providing me with accurate and (almost) real-time water temperature, making pool maintenance much easier. From here, I can create automations to turn the heater on, send a message on family group when the temperature is ideal, and much more.

Enjoy o/

References

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