Connecting a SONOFF door/window sensor to a remote system via LoRa (Long Range)

eWeLink CUBE
1

Does anyone know how to transmit the signal from a SONOFF SNZB-04P Zigbee door/window sensor located 500 meters away from a home automation system based on a SONOFF Zigbee Bridge Ultra hub or i-Host?

I’ve heard that a LoRa system—using a battery-powered (3.6V) transmitter at the source and a corresponding receiver at the destination, along with the right software or API—might work.

However, I am unfamiliar with the specific details of the process on both the transmission and reception ends. I have some fluxes in NodeRED.

Perhaps an iHost would be more useful than the aforementioned bridge (ZB Ultra) for the receiving end, utilizing a Docker add-on.

2

I don’t know if its a practical suggestion in your case but I use ESP32 boards with Openmqtt to integrate BLE into my iHost, using Node-red. I have seen references that this same setup could integrate Lora.

3

The LoRa idea, as suggested by @john.e.dixon, is certainly worth exploring. However, you can’t directly retransmit the SNZB-04P’s Zigbee signal over LoRa. You would need a Zigbee receiver near the sensor to capture its state, then forward the events over LoRa to a receiver connected to your iHost, where Node-RED could process them.

Alternatively, a standalone contact sensor with an ESP32 and LoRa module might be simpler.

The key questions are whether you have line of sight over the 500 m distance and whether you need to keep using the original SONOFF sensor.

4

Thanks for your replies, @john.e.dixon and @jam3.

I realize that directly retransmitting the SNZB-04P signal via LoRa presents a fundamental challenge.

Another key aspect regarding the signal source is the lack of mains power; the only available power source would be one or more 3.6V batteries.

Therefore, I think it makes more sense to use a standalone contact sensor other than the SNZB-04P—specifically, one that connects directly to an ESP32 board equipped with LoRa transmission capabilities.

Where could I find such an ESP32 board with LoRa transmission (TX) for the signal source?

For signal reception, I would need a LoRa receiver board (RX) and then, somehow, send that signal to the i-Host’s Node-RED.

Where could I find that LoRa RX?

Ideally, the standalone sensor would be wireless rather than wired.

So, the answers to the key questions are:

1.- The distance is 500 meters, but there is no line of sight. There is vegetation, some buildings, and a change in elevation.

2.- Regarding the signal source, we can rule out the SNZB-04P.

5

Given the lack of mains power at the remote location, I’d consider a conventional RF solution. LoRa offers excellent receiver sensitivity and good range at low power, but it isn’t necessarily the only option. A simple battery-powered RF transmitter, sending a short burst only when the contact changes state, could be very energy-efficient.

With a suitable receiver and a directional antenna at the house, a conventional RF link might also work over 500 m. The lack of line of sight makes both solutions more challenging, so the actual terrain and antenna placement will be decisive.

Obviously, LoRa offers more flexibility and built-in communication features, while a simple RF system could be much cheaper and less complex. I’d compare both based on the required reliability, battery life and ease of integration with the iHost/Node-RED.

However, I’m not aware of a straightforward, off-the-shelf kit that I could confidently recommend for your exact requirements: 500 m without line of sight, battery operation and integration with iHost. There are no obvious plug-and-play solutions here, and modifying an existing RF sensor with a power amplifier and a suitable antenna is possible.

SONOFF has also offered RF-based sensors, which could provide a starting point. If you have the necessary RF expertise, modifying the transmitter with an additional power stage and a suitable antenna may be an option. Alternatively, someone with the right experience could help with that. Either way, this is no longer a simple plug-and-play project, particularly given the 500 m distance and lack of line of sight.

That said, this is probably beyond the scope of the eWeLink forum. People here may be able to point you in the right direction, but for detailed technical guidance on designing a long-range RF or LoRa link, you’d be better off asking in a specialist radio communications or LoRa community. There are probably several suitable forums where people discuss exactly these kinds of projects.

6

I think @jam3 's idea for RF is probably good enough to cover 500m; not necessary to use Lora which can work up to 10km.
The ESP boards for both can be found on Aliexpres without any bother.

I recommend OpenMQTT flashed onto the ESP board to connect to Node-red. This allows you to integrate directly via the MQTT-in node, which is what I do with all my BLE sensors.
To get some ideas take a look at https://youtu.be/_gdXR1uklaY?is=uKog4IHL6sqPZVis
and also other vídeos on this channel for both 433 and Lora.