Home Improvement → [Landscaping] Anyone Build their own rain sensor?

I have a hunter sprinkler system. I get tired of either watering the lawn when it's raining, or remembering to turn off/on the system if it is sunny/raining, etc.

I see what you can purchase a rain sensor for some what cheap, but I was wondering if anyone had built their own, if so, how did it go, etc? I am considering making my own, mainly for the fun of it.

This is a problem to which there are many solutions. There's dozens of different ways to design a rain sensor, some very simple, and some can get very complex.

Most commercial rain sensors for irrigation systems use discs of absorbent material. When the discs get wet, they expand slightly and activate a mechanical switch.

But perhaps the easiest to achieve DIY might be absorbent material with a couple electrodes in it. When wet, electricity will pass between the electrodes. A simple comparator circuit could then activate a relay when moisture is detected.

The trick with such sensors though, is that the type of absorbent material used is critical to how the device will perform. Ideally, it should get wet and dry off at about the same rate as the soil.

It can also get very complex. Some rain sensors used for meteorological observations use capacitive or optical (infrared) methods to detect precipitation, or a combination of both. This would be coupled with a microprocessor and mathematical algorithms to determine the approximate type and amound of precipitation.

Another approach called a "tipping bucket" can be used to accurately measure rainfall amount.

And there's lots more. Depends how much time and effort you want to put into it.

I tried several types of water sensors in the rain. The cheap one from Olimex works quite well even in very light rain but you have to protect the wire to the sensor and of course rest of the electronics. Lots of DIY weather stations use it - search Google.

*** Just thought of a better sensor for a solution which measures total amount of rainfall to decide if you want to water or not. Use a standard diameter rain gauge with a Milon eTape to measure the height. »www.milonetech.com/About ··· Tape.php

I am actually working to make a more high-tech solution.
As I have a server running 24/7, I plan on writing code to query a weather service and get past rain info and forecast. Then trigger a remote relay to make/break the sensor contact.
This way I can not only prevent the irrigation when there has been enough rain recently, but also prevent it when rain is forecast very soon.

Yeah, I just bought one of these. »www.rainmachine.com/

It's easier.

Seems that buying a 21.00 out of the box sensor might be the most time effective

And you thought you could DIY for cheaper such an electronic device?

That is an amazing deal ... but behind the flashy GUI, it is actually similar to the web-query method proposed by cowboyro .

Actual rainfall in YOUR YARD may not match the local forecast or history. My son once came home from school totally drenched but it did not rain at home.

It is possible that some other commercial device exists which measure actual rainfall, but they will probably cost a lot more than DIY.

The difference is that I have a weather station, so I can get past/current rainfall amount