If you have an old-style gasmeter to measure gas consumption it's still possible to turn it into a smart device.
- basic solder skills
- Raspberry Pi with free connectors
- MQTT Server
The software works on the hardware of the magnetic sensor QMC5883L. Find assembly instructions in german or here in english version.
Note: The above Tutorials are referencing the HMC5883L hardware from Honeywell while this software takes care for QMC5883L - the chinese version of the chip. For hardware assembly this makes no difference but software will differ!
Before running this Software you need to check hardware is basically working:
[03:13:20] openhabian@openhab:~$ i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- 0d -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
The software is written in python3. If
python3 --version
returns a valid result you're fine. Otherwise follow the install instructions
Now switch to your desired directory and clone the repo
git clone https://github.com/weymann/smartmeter-gas.git
Install the needed python modules to enable hardware access plus distributing data via MQTT
- QMC5883L python driver
- Paho MQTT for data distribution
Check if dependencies are solved with a quick call
smartmeter_gas.py help
Configuration is stored in config.json in the same directoy as the python script. Basically three sections needs to be configured:
- hardware configuration of values which shall trigger a count
- MQTT configuration to distribute data
- some technical data from your gas bill to calculate kwh consumption and pricing
{
"device_measure_field" : 0,
"device_upper_bound" : 0,
"device_lower_bound" : -3000,
"mqtt_server" : "whereever.youwant.com",
"mqtt_port" : 8883,
"mqtt_user" : "user",
"mqtt_pwd" : "password",
"mqtt_topic" : "home/smartmeter/gas",
"cert_location" : "/etc/ssl/certs/ca-certificates.crt",
"z_number" : 0.955,
"heating_value" : 10.308,
"gas_price" : 0.0578,
"gas_fee_month" : 6
}
Figure out your device settings running the script with parameter setup
smartmeter_gas.py setup
Each second a log output is given with the current measured values. Find a time slot when gas is consumed. The example in the picture below is showing the changes during consumption - values are going down from approx 1000 to -4000 and up again. Record such a cycle and derive your config
device_measure_field- column of the desired measurement (green)device_upper_bound- value to enter state count (blue)device_lower_bound- value to exit state count (orange)
In order to calculate kwh consumption and a corresponding price take your latest bill. You should find the z-number and heating value somewhere. If this isn't declared leave it to the already defined values in config json. It's a fair assumption: 1 m3 ~ 10 kwh.
Pricing should be found in your bill. Prices in the below german example are ex vat so you need add the tax rate in order to get the paying price.
You should be aware of your mqtt settings.
If not encrypted change the mqtt_port to 1883 and leave the cert_location empty.
If even anonymous is allowed leave mqtt_user and mqtt_pwd empty.
Use e.g. MQTT Explorer to check my IoT devices. You'll see the current values in the left tree and on the right side history for the selected topic is found.
This screenshot shows already the provided values. Below table gives more details
- Prefix Topic is given in configuration.
- Values marked with Write can be overwritten with publish.
| Sub-topic | Name | Write | Description |
|---|---|---|---|
| / | total | X | total gas count in dm3 this should match to the origin counter |
| / | timestamp | timestamp of last measurement | |
| / | success-rate | daily read success rate of the magnetic sensor | |
| /config | heating-value | X | heating value from your gas bill |
| /config | z-number | X | Z-number from your gas bill |
| /config | gas-price | X | kwh gas price from your bill |
| /config | gas-fee | X | monthly fee from your gas bill |
| /day | count | daily gas consumption in dm3</ | |
| /day | kwh | daily gas consumption in | |
| /day | price | daily price incl. partial fee | |
| /month | count | monthly gas consumption in dm3 | |
| /month | kwh | monthly gas consumption in kwh | |
| /month | price | monthly price incl. monthly fee | |
| /year | count | yearly gas consumption in dm3 | |
| /year | kwh | yearly gas consumption in kwh | |
| /year | price | yearly price incl. monthly fees till today |
Values from day / month / year are published in yesterday / previous-month / previous-year after the timeframe ended.
The kwh and price values of the configuration can be changed with a simple publish call e.g. using the MQTT Explorer. So if you receive a new bill adapt the new values and publish them - no software restart necessary.
It's also possible due to some miscounting or device errors the reported total counter and the real measured counter diverges. From time to time check the counter manually. If the number from this smartmeter doesn't match simply publish the correct counter value - no software restart necessary.
Great! You turned an old fashioned gas meter which needs to be checked manually into a full fashioned auto reporting smart meter.
Use now your data and put it into your favorite Smarthome Software. I use openHAB which provides the capability to receive MQTT data.
