In this guide, we'll explore how to transform an easily accessible Aqara Water Leak Sensor into an instantaneous rain meter. Requiring no soldering skills and only a handful of jumper wires and a rain sensor board, this project is a breeze to complete. With a simple setup process and seamless integration with Home Assistant, as long as you're already utilizing Zigbee and have a hub in place, you'll be good to go.
Choosing the right sensors
It's worth noting that when shopping for an Aqara sensor, you may come across a newer version with the suffix T1. These Aqara T1 devices boast Zigbee certification and employ Zigbee 3.0. In this particular case, however, the Aqara Water Leak Sensor T1 is only verified to be compatible with Zigbee2MQTT and ZiGate. While the T1 variant is a solid choice, the non-T1 version offers broader compatibility.
I've consistently admired Aqara Zigbee products for their sleek designs, affordability, and remarkable accuracy. They embody the very essence of practical smart home products that I appreciate. Moreover, as this project demonstrates, they can be effortlessly repurposed to serve a distinct function than originally intended.
The crux of this project lies in the use of a rain sensor, which features a series of exposed traces on one side. These traces are not interconnected but are in close enough proximity to be bridged by raindrops. As a result, the moment the first raindrop falls, the circuit is closed, instantaneously altering the binary status of the Aqara Water Leak Sensor.
How to attach a rain sensor to an Aqara Water Leak Sensor
The fact that the Aqara Water Leak Sensor has two probes on its underside, to which you can attach any binary sensor, makes this project a lot easier. There is absolutely no soldering involved. All you need is a hex screwdriver to loosen the probes.
Most rain sensors will come with a daughterboard (sometimes also called the control board), which will turn the digital signal (on/off) in to an analogue signal, which can report the exact impedance back to the controller. This project only uses the rain sensor, so it will only report whether it is raining or not, and not how much water is on the board.
The rain sensor will have two pins on one of its sides, which you can easily attach to the probes using two jumper wires. To make things a bit more secure, I would use some hot glue to attach the wire to the sensor more permanently.
Where to place the rain meter
As the Aqara Water Leak Sensor is IP67-rated, it should survive in a body of water up to a meter deep for half an hour. For you, that means that you needn't be too picky about where to place your newly constructed rain meter.
There are also numerous 3D prints available for exactly this project. Just make sure you buy a rain sensor that fits the slot, or you will have to manually adjust the model.
Possible issues with the Aqara rain meter
Depending on where you live, the nighttime humidity might be enough to trigger the sensor, as the creator of this 3D model found out. But as you're unlikely to need a rain meter during the night, you might be able to live with it.
Another issue is that the rain sensor isn't heated as it would be on many commercially available products. While your sensor will immediately react to rain, it might take some time for it to be able to report that it isn't raining any more.
Finally, a shoddily constructed rain meter will degrade over time. The traces might rust, or the jumper wires come loose. If you do want to extend the lifetime of your rain meter, make sure you give it proper protection by placing everything that doesn't need to be exposed into a chassis.