Gas Meter Smart Meter Reader for BK-G4 MT

With this model, a **Honeywell BK-G4 MT gas meter** can be made smart and integrated into **Home Assistant**

The Gas Smart Meter Reader consists of a 3D-printed housing/holder, a **Wemos D1 Mini / ESP8266**, and a directly soldered **reed switch**. The reed switch detects the gas meter's pulses. ESPHome counts these pulses and calculates the gas consumption in m³ from them

This way, the current meter reading or gas consumption can be automatically displayed in Home Assistant and used, for example, in the energy dashboard

The reed switch is soldered directly onto the Wemos D1 Mini board. No separate sensor cable is needed

On my Honeywell BK-G4 MT it states:

**1 imp = 0.01 m³**

This corresponds to:

**100 pulses = 1 m³**

Important Safety Notice

This model does **not** interfere with the gas meter. It is only attached externally

Nothing on the gas meter is opened, altered, or seals tampered with. The Gas Smart Meter Reader is only attached to the outside of the meter

Work on gas installations, gas pipes, or sealed parts may only be carried out by qualified personnel

In case of gas smell or uncertainty, immediately contact the responsible network operator or specialist company

Required Parts

• 1× 3D-printed housing / holder
• 1× Wemos D1 Mini / ESP8266
• 1× Reed switch in elongated design
• Optional: some glue or hot glue for fixing the board

Used Reed Switch

I used an elongated reed switch / magnetic switch

The alignment of the reed switch is important:

The **seam on the reed switch must point to the side**

The seam must **not point upwards towards the gas meter**. If the seam is misaligned, the reed switch may not detect any pulses or only unreliable ones

Before final assembly, the function should be tested

Wiring

The reed switch is soldered directly onto the Wemos D1 Mini pins and used like a simple switch

In the ESPHome configuration, the internal pull-up is activated for GPIO5:

mode: INPUT_PULLUP

This eliminates the need for an additional pull-up resistor

Assembly

1. Solder the reed switch directly onto the Wemos D1 Mini board
2. Use D1 / GPIO5 and GND for this
3. Ensure that the seam of the reed switch is later aligned to the side
4. Insert the Wemos D1 Mini into the printed housing
5. Place the reed switch into the designated groove
6. Position the Gas Smart Meter Reader on the outside of the Honeywell BK-G4 MT
7. Connect the device to ESPHome
8. Check in Home Assistant if pulses are detected
9. If no pulses are detected, slightly move the housing or the reed switch and test again

Meter Factor

On the Honeywell BK-G4 MT meter, it states:

1 imp = 0.01 m³

This implies:

100 pulses = 1 m³

In ESPHome, gas consumption is therefore calculated as follows:

Gas consumption = pulses × 0.01

If the current meter reading is to be adopted, the starting value must be entered in pulses:

Pulses = current meter reading in m³ × 100

Example:

Meter reading: 3278.29 m³ Start value: 327829

This value is entered in the ESPHome configuration for initial_value

ESPHome Example Configuration

# ============================================
# ESPHome configuration for Gas Smart Meter Reader
# Honeywell BK-G4 MT + Wemos D1 Mini + Reed switch
# ============================================

esphome:
 name: gas-smartmeterreader
 friendly_name: Gas Smart Meter Reader

esp8266:
 board: d1_mini
 restore_from_flash: true

preferences:
 flash_write_interval: 5min

logger:

api:
 encryption:
   key: !secret gas_smr_api_encryption_key

 services:
   - service: update_counter_pulses
     variables:
       counter_pulses: int
     then:
       - globals.set:
           id: total_pulses
           value: !lambda 'return counter_pulses;'

ota:
 - platform: esphome
   password: !secret gas_smr_ota_password

wifi:
 ssid: !secret wifi_ssid
 password: !secret wifi_password
 min_auth_mode: WPA2

 ap:
   ssid: "Gas-Smartmeterreader"
   password: !secret gas_smr_ap_password

captive_portal:

globals:
 - id: total_pulses
   type: int
   restore_value: true
   initial_value: '0'   # Enter the current meter reading in pulses here

binary_sensor:
 - platform: gpio
   id: internal_pulse_counter
   pin:
     number: GPIO5       # D1 on Wemos D1 Mini
     mode: INPUT_PULLUP
   name: "Live Pulse"
   filters:
     - delayed_on: 100ms
   on_press:
     then:
       - lambda: id(total_pulses) += 1;
       - output.turn_off: led
   on_release:
     then:
       - output.turn_on: led

sensor:
 - platform: template
   name: "Gas Consumption"
   device_class: gas
   unit_of_measurement: "m³"
   state_class: "total_increasing"
   icon: "mdi:fire"
   accuracy_decimals: 2
   lambda: |-
     return id(total_pulses) * 0.01;
   update_interval: 60s

 - platform: wifi_signal
   name: "WiFi Signal"
   id: wifi_dbm
   update_interval: 60s

 - platform: uptime
   name: "Uptime"
   id: device_uptime

output:
 - platform: gpio
   pin: GPIO2            # D4 / internal LED
   id: led
   inverted: true

Home Assistant

The sensor is created in Home Assistant as gas consumption with the unit m³

The ESPHome configuration uses:

device_class: gas state_class: total_increasing unit_of_measurement: "m³"

This allows the sensor to be used in the Home Assistant energy dashboard, provided Home Assistant correctly recognizes the sensor

Print Settings

I printed the model with the **standard print profile**

A normal standard profile with a 0.4 mm nozzle was used. No special settings were required for me

PLA or PETG is suitable as a material. For warmer rooms or permanent use, PETG is recommended

Notes

This model was created and tested for my **Honeywell BK-G4 MT**

Other gas meters may have different housing shapes or sensor positions. In this case, the Gas Smart Meter Reader may not fit, or the reed switch may need to be positioned differently

The ESPHome configuration must be adapted to your own Wi-Fi, your own secrets, and the current meter reading

The starting value initial_value should not simply be adopted, but must be calculated to match your own gas meter

DE:

Wenn du das Modell gedruckt hast, freue ich mich sehr über eine Bewertung, einen Kommentar oder ein Make. Schreib gern dazu, was dir gefällt oder was ich verbessern kann – so werden die Modelle für alle besser.

EN:

If you printed this model, I’d really appreciate a rating, comment, or make. Feel free to share what you liked or what could be improved – it helps make the models better for everyone.