There’s an old proverb algebra teachers often recite: You have to use what you know to find out what you don’t know. The same could be said about sensors. For example, analog to digital converters use something computers are good at finding (like time) and use it to determine something they aren’t good at finding (like voltage). So how do you detect rainfall? If you are [lowflyerUK], you use the microphone in your web camera and a Raspberry Pi.
The idea was to reduce irrigation usage based on rainfall, so an exact measurement isn’t necessary. The Python code that analyzes the audio input is calibrated with three configuration parameters and attempts to remove wind noise. Even so, it needs to be in a room that gets a lot of noise from rainfall and ambient noise can throw the reading off.
The weather service is never going to adopt this system. Still, it is a great example of taking something you know and using it to get something you don’t know. If you want a more complete weather station, we have a few options for you.
Now you can find out how hard it is raining outside without leaving the confines of your mancave/womancave. Pictured above is the sensor portion of what [Frapedia] calls his visual rain sensor.
Most rain gauges just use a graduated cylinder to capture water as it falls from the sky. That will give you a reasonably accurate measure of how much it rained, but it tells you nothing about how hard it rained. The measurement made here is based on sound. The harder it rains, the lounder the sound will be from water hitting an up-turned metal bowl. The unit above turns the system on when water bridges the traces, then a microphone is used to monitor the sound from the bowl. This is visualized by a VU-meter chip on a column of LEDs mounted inside the house.
After the break you can see the project box that houses the status display. We say it’s too small an needs to be replaced with a much larger LED meter.
Continue reading “Visual rain sensor — so you never have to look outside”
One thing that annoyed [Jashua] to no end was hearing his automated sprinkler system kick on in the middle of the night, when it had rained earlier in the day. He wished that his sprinklers were a bit smarter, so he decided to give the system an upgrade.
Rather than pay hundreds of dollars for a more sophisticated automation system, he spent about $45 on supplies and scrounged together some items he had sitting around the house to make a rain-sensing module of his own.
The resulting project, Pysprinklers, uses Python along with a handful of components to better manage his water usage. He got his hands on a cheap rain gauge, and modified it with a game controller and a set of magnetic surface contacts. If there has been a significant amount of rain in the last 24 hours, his system will prevent the sprinklers from turning on. Additionally, if there is rain in the forecast, the sprinklers will be delayed a bit to see if rain makes its way into the area.
We’re all for saving money (and water), so we think [Jashua’s] system looks great, especially because he ended up using a handful of things he already had on hand.