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PM2.5 Air Quality Kit (SHT30)

Unit PoE Cam W v1.1 Kit

Sensor

Unit ENV-IV

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Unit MQ

Unit AMeter

Unit VMeter

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Unit VMeter Home Assistant Integration

Unit VMeter is a voltage sensor for real-time voltage monitoring. It uses a 16-bit ADC converter ADS1115 internally and communicates over I2C (0x49).

Note
Because Unit VMeter is only a standalone sensor platform, an additional host device (such as Atom Lite, Core2, CoreS3, etc.) is required to integrate it into Home Assistant

Get the latest ADS1115 configuration from ESPHome

Configure the sensor

You need to enable the I²C component in your ESPHome configuration:

yaml
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# Example configuration entry for ESP32
i2c:
  sda: GPIOXX
  scl: GPIOXX
  scan: true

The GPIO pins here will vary depending on the host device used. For example, when using Atom Lite as the host:

yaml
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# I2C Bus on Grove Port (HY2.0-4P)
i2c:
  sda: GPIO26
  scl: GPIO32

Unit VMeter configuration example

  • First, configure the base component ADS1115
yaml
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ads1115:
  - address: 0x49

sensor:
  - platform: ads1115
    multiplexer: "A0_A1"
    gain: 1.024
    sample_rate: 128
    name: "Unit VMeter A0_A1 Ref"
    id: diff
    update_interval: 10s
Tip
Unit VMeter only uses the AIN0 and AIN1 channels, so you can use up to 3 multiplexer options: "A0_A1", "A0_GND", "A1_GND"; for voltage measurement this configuration uses only A0_A1.
  • Configure EEPROM to read calibration parameters and create custom data using a Template sensor
yaml
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i2c_device:
  id: eeprom
  address: 0x53

sensor:
  # Previous ads1115 declarations
  ...
  - platform: template
    name: "Input Voltage"
    id: input_volt
    unit_of_measurement: "V"
    icon: "mdi:flash"
    accuracy_decimals: 2
    update_interval: 10s
    lambda: |-

      float d = id(diff).state;

      if (isnan(d)) return NAN;

      const float PRESSURE_COEFF = 0.015918958f;

      // Remember to change the 'EEPROM_REG' if you changed the 'gain'
      const uint8_t EEPROM_REG = 0xE8;

      uint8_t calib[8];
      uint16_t hope, actual;

      // Read EEPROM
      if ( id(eeprom).read_register(EEPROM_REG, calib, 8) != i2c::ERROR_OK ) {
        ESP_LOGD("vmeter.sensor", "Failed to read from EEPROM..");
        return NAN;
      }

      uint8_t xor_result = 0x00;

      for (uint8_t i = 0; i < 5; i++) {
          xor_result ^= calib[i];
      }

      if (xor_result != calib[5]) {
          return NAN;
      }

      hope   = (calib[1] << 8) | calib[2];
      actual = (calib[3] << 8) | calib[4];

      float calibration_ratio = (float)hope / actual;

      ESP_LOGD("vmeter.sensor", "Factory calibration factor: %f", calibration_ratio);
      
      float vin = - d / PRESSURE_COEFF;
      vin = vin * calibration_ratio;

      return vin;

When reading the EEPROM, you need to change the EEPROM_REG read address in the lambda expression according to the gain value set for ADS1115:

c++
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// In lambda expression
// remember to change the 'EEPROM_REG' if you changed the 'gain'
// for an example, when 'gain' is 1.024
const uint8_t EEPROM_REG = 0xE8;
ADS1115 Gain EEPROM Data Register Max Input Voltage (theory)
6.144 0xD0 -
4.096 0xD8 -
2.048 0xE0 -
1.024 0xE8 64 V
0.512 0xF0 32 V
0.256 0xF8 16 V

Recommended gain values are 0.256, 0.512 and 1.024; among them, for voltages below 16V resolution is 1mV, for voltages above 16V resolution is 7.9mV. Choose the appropriate gain value and the corresponding calibration parameters read from EEPROM according to the voltage under test. For accurate data, only one of AIN0 or AIN1 can be measured; do not connect both channels to voltage inputs.

WARNING
The product's designed optimal measurement range is ±36V. Do not input voltages outside this range to avoid device damage; the EEPROM (0x53) contains factory calibration parameters — do not perform write operations to the EEPROM, otherwise calibration data may be overwritten and measurements may become inaccurate.

Add the sensor to Home Assistant

After adding it to the Dashboard, you can view the sensor data in Home Assistant

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