As I am (still) using a gas boiler I need to monitor gas leakage to ensure that if it happens I am aware before it caused any damage.
In the past, I was using "dumb" sensors with only sound/led indication of the leak. Now, as it was time to replace the old sensor anyway, I decided to try something more intelligent.
Some of the criteria I was using to find the device:
- It should be able to work autonomously, with a sound leak alarm no matter what.
- It should use standard WIFI. I already have coverage of the entire house with WIFI and I see very little value in using other wireless protocols and their gateways.
- It should use open standards and should be able to operate without any kind of cloud connectivity. It is very important to me to have the device fully functional even if the vendor will decide to shut down its own cloud servers or "end of life" the current protocol.
After all, I found that the "Shelly Gas" sensor meets all the criteria – according to specification it supports MQTT, REST and can work without vendor app/cloud connectivity. So, I decided to give it a try.
Device experience
The device seems to be built on the Expressif platform (using Mongoose-OS) and once turned on provides an Access Point to connect. Once connected it is possible to configure the device using a web browser and switch it to client mode. I have a dedicated SSID for home IoT devices, without internet connectivity, so I decided to use it. After configuration device successfully acquired an IP address using DHCP and was available on it for the configuration.
There is not too much to configure – "eco mode", buzzer volume, and 3 actions. Actions are webhooks with user-defined URLs triggered on alarm status change (mild/heavy/gone). There are also settings to enable and configure MQTT and CoIoT protocols. It is also possible to control a smart gas valve with it, however, I do not have such.
Getting data from the device
I decided to integrate the device with Grafana, to build real-time graphs and use its alerting functionality. To push data in the InfluxDB I am already using Telegraf, so it was logical to integrate it with Shelly Gas.
The device itself has an HTTP server that serves UI and API. Vendor provides a very detailed description of the device API.
To grab device data I was using /status HTTP endpoint. Here is a sample reply:
{
"wifi_sta": {
"connected": true,
"ssid": "IOT",
"ip": "192.168.1.10",
"rssi": -54
},
"cloud": {
"enabled": false,
"connected": false
},
"mqtt": {
"connected": false
},
"time": "18:22",
"unixtime": 1675617720,
"serial": 59,
"has_update": false,
"mac": "10521CF2AAAA",
"cfg_changed_cnt": 0,
"actions_stats": {
"skipped": 0
},
"gas_sensor": {
"sensor_state": "normal",
"self_test_state": "not_completed",
"alarm_state": "none"
},
"concentration": {
"ppm": 0,
"is_valid": true
},
"valves": [
{
"state": "not_connected"
}
],
"update": {
"status": "unknown",
"has_update": false,
"new_version": "",
"old_version": "20221027-111245/v1.12.1-ga9117d3"
},
"ram_total": 52528,
"ram_free": 39640,
"fs_size": 233681,
"fs_free": 92368,
"uptime": 187828
}
What I like is that device provides all required data in a single HTTP call and uses JSON format, so it was very easy to integrate it.
Building Grafana dashboard
To get data from the device in the InfluxDB I used the following configuration:
[[inputs.http]]
urls = [
"http://192.168.1.10/status"
]
tagexclude = ["url", "host"]
data_format = "json_v2"
[[inputs.http.json_v2]]
measurement_name = "shellygas"
[[inputs.http.json_v2.tag]]
path = "wifi_sta.ip"
rename = "ip"
[[inputs.http.json_v2.tag]]
path = "mac"
[[inputs.http.json_v2.field]]
path = "concentration.ppm"
rename = "concentration"
type = "int"
[[inputs.http.json_v2.field]]
path = "gas_sensor.sensor_state"
rename = "sensor_state"
[[inputs.http.json_v2.field]]
path = "gas_sensor.alarm_state"
rename = "alarm_state"
[[inputs.http.json_v2.field]]
path = "ram_total"
type = "int"
[[inputs.http.json_v2.field]]
path = "ram_free"
type = "int"
[[inputs.http.json_v2.field]]
path = "fs_size"
type = "int"
[[inputs.http.json_v2.field]]
path = "fs_free"
type = "int"
Once restarted Telegraf started to poll the device every 10s and push data to InfluxDB. Here is a sample dashboard I created:
The exported version could be downloaded from my GitHub.
Testing
To test the device I used dust-off compressed gas aerosol. Once the concentration is high enough device starts sound/audio indication and the PPM counter is also increasing. Here is a Grafana output of the test:
More things to do
Connect the device to the Domoticz using the MQTT protocol
- Configure alerts for the device status and availability
- Think about integration of the device alerts with SMS (using AWS SNS?) and email
Conclusion
I like the way Shelly built the device – it has cloud integration but it is optional. Support of open and well-documented protocols allowed me to easily integrate it into my setup.
smallhacks 