I am not actually measuring rain with it, just the output from my dehumidifier. This is the one I am using:
I have an older version of it that I used outside, it has a bigger collection system and a removable screen. I don’t know that they make it anymore. It worked quite well as far as I knew.
For my dehumidifier, I took apart the gauge part and soldered a three conductor cable, +power, gnd, and switched side of the reed switch. I hooked these up to a NodeMCU that is running Tasmota
The reed switch goes to one of the digital inputs, where I have it set up as a pulse counter. Every 30s it uses MQTT to send information about its sensors. I have POW that measures the power and energy used by the dehumidifier and sends it to MQTT. It too is running Tasmota.
I have NodeRED running and there is a flow on it that subscribes to the topic and gets the updates. It parses the string into JSON and then grabs the counter. There is some math to figure out the starting counter and power and then the ending one and calculate the efficiency.
Here is the dehumidifier one:
And the measuring one:
And here is what the power and energy efficiency graph looks like:
it took me a little while to get to the point where I had good and efficient control. The graph is telling, you can see when the compressor starts (zooming in shows the fan too). Notice how the compressor has to run for several mins before any water starts coming out. Also note that the efficiency droops on some of the runs. The coils are probably starting to ice there. What is more interesting is how long it takes for all the water to come out and be counted. The compressor typically runs for about 30min. It takes about that long again before all the water it created makes it out. The typical control for one of these would basically short cycle the compressor, i.e. it is on for about 5-10min and then off for the same amount. The fan would be running the whole time (it uses about 60-80W) and it would be blowing much of the condensed water back into the air, so the temperature of the room would increase significantly too. (All that energy has to go somewhere.)
The rain gauge has 200 bucket tips per cup, so right now I am getting about 3.2 cups/KWhr (about 0.75liter/KWh). It is about 18C and I aim to keep the humidity below 60% on average to keep mold from growing.
Here are the temps and humidity of the input air:
There is a Heat Pump Water Heater in a nearby room and it cools the space. This is why there was a rise from just before 02:00 to 07:00. The HPWH was off then. It is typically on for 18 hours a day, but it only draws about 500W in heat pump mode, so it is much less energy usage in total than when it uses its element.
