Abstract

One of the sophisticated features of Rain Machine is its ability to tie in weather to the watering schedule. Using prediction logic and information gathered by weather sits, it determine if there is too much or too little water. In other words it can alter the watering schedule to be “just right”. This all works well if the predicted rainfall does occur but should it not, the lawn can suffer.

In my area of the country, a thunder storm is usually predicted to occur each day. However having them actually happen or even hit my area and deposit enough Rain is a crap shoot. More often than not, the rain may miss or drop a sprinkle far less than what the weather site predicted. Yet the next town over may have gotten slaughtered by rain.

The purpose of this writeup is to combine the rain sensor to the Rain Machine prediction logic so that rain confirmation and scheduling can occur accurately.

Rain Sensors

In general a rain sensor is a set of water absorbing discs that expand based upon a given amount of water. Depending upon the device employed, they can be set for certain amounts of water “inches” before signaling they reached their threshold. In turn, devices such as Rain Machine use this binary on/off signal to determine that a rain fall amount has been achieved.

Later, depending upon the weather the water evaporates and signals the watering device that it can resume watering. In essence, there are two valuable pieces of information here. First is the detection of water meeting a specific threshold and second, the amount of time it takes for the water to evaporate and re-enable the sensor.

Although there are a plethora of sensors offered, they all work pretty much the same way using water absorbing discs. For this feature to work with Rain Machine, it would need to know the tripping point for what the rain sensor is set to. In other words, if the sensor is set to trip at .5 inches of water, Rain Machine would need to know this as well confirming that at minimum, the amount of rain has fallen.

Theory of operation

With the rain sensor enabled along with the “smart confirmation”, Rain Machine will combine its rain prediction logic with the rain sensor as confirmation that the rain occurred.

Rather than base its watering cycle on a predicted amount of rain, Rain Machine will also rely on the rain sensor to confirm that the amount of rain fall has taken place. This confirmation offers the user two vital functions:

1. The ability to notify Rain Machine whenever rain has occurred and a threshold has been reached. This is the functionality that the rain sensor provides now.
2. Should rain be predicted, the rain sensor would be used to confirm that the rain occurred allowing it to accurately change the watering schedule due to sufficient water amounts.

Finally, the amount of time it takes for the rain sensor to reset is also vital. This amount of time if calibrated could be used to tell how fast the soil dries out after a rain fall. In essence, should a rain fall occur and the sensor is triggered yet an hour later it resets, Rain Machine could tell that the rainfall was small and or the heat conditions are high enforcing strong evaporative condition.