20 USD for a sdr with rtl_433 compatibility¹. Like this NooElec USB stick link privided by @Stolid on the chat. @AngularSpecter was giving this github link fro Realtek RTL2832 based DVB dongles. Haven’t found solid documentation still.
I need to choose which is the quickest and nafest path to connect it with this gas sensor
I’m not sure about the others but I can tell you about the sonoff. I flashed mine with espurina and configured it as an mqtt bridge. In this mode, it forwards any sensor data it receives to a single mqtt channel that you configure. The payload contains the sensor data ( a big hex packet ), a timestamp and some other metadata. To be useful, you have to write middleware to translate the sensor data into something you can use. I had to write a python daemon that subscribes to the in topic, does the regex and translation then publishes a new topic for home assistant to work from.
Something else to consider is that not all 433 is the same. Sensors may use a modulation that doesn’t work with your bridge. I’m using a non-somoff sensor with mine, but I had to hunt to make sure it would work.
Another option not on your list is an sdr with rtl_433. It’s a cheap solution that will work with a huge variety of sensors ( including a lot of wireless weather stations ) but it is rx only and will require some coding to get up and running and possibly some reverse engineering of the signal if it isn’t already supported.
Thanks for the sdr link, I’ve added it to the list.
Is in your opinion the extra middleware code needed in the first, more expensive solution?
Did you have experience with that product?
Did you release you Python code?
I believe the middleware is required. The bridge publishes everything to the same mqtt topic and the sensor data is all in the payload. So to make sense of it, you have to bitmask the payload to extract the sensor ID and sensor state. I don’t believe you can template that out in the mqtt sensor inside home assistant.
I can post my middleware code for the sonoff bridge tonight. Unfortunately, rtl433 doesn’t have a built in demodulator for these sensors and I haven’t had a chance to write one yet, but that would likely require some middleware as well as you still need the logic to properly do the mqtt publishing
I don’t quite agree with mjbeals regarding middleware in case of Sonoff RF bridge (Espurna) + HA.
Correct me if I’m wrong, but it seems like TS wants to create a system that picks up a RF alarm signal from a gas leak sensor and pass it to HA, which in turn will react somehow - notify user, play sound etc.
In such case it’s just an ordinary detector, and the only meaningful information is change of its state (i.e when it sends a signal).
I’m working on a system with a Sonof PIR sensor, Sonoff RF bridge (Espurna) and HA@RPi3.
From my point of view, the goal is the same.
RF bridge treats sensor as a relay, so you receive a clear MQTT message that the relay is on or off. I currently use MQTT switch component in HA, and the only thing I need to take care of is to set the relay off after say, 5 seconds, otherwise it remains constantly ON. No middleware so far.
Can post my configs and explain my views on various RF bridges if necessary.
However, mjbeals is right that Sonoff RF bridge is simple and works with Sonoff sensors, but there is no guarantee it will work with third-party sensors despite them being marked as 433MHz.