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Rain Sensor

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grkmr

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Hi all,

I'm responsible to build a rain sensor with the help of PIC programming. However, I don't know in which stage I should use it.
Project is simply to detect water and run an engine using the data that comes from the sensor. I plan such a circuit basically:

Water ---> Sensor ---> PIC ---> (Amplifier if needed) ---> Engine

The main problem is that I don't know what kind of code should I use in PIC, what is the purpose of PIC? Will it work as an DAC(Digital to analog circuit)?

Thanks!
 
Things you should be thinking about:

What is the basis of the sensor? What measurable property is effected by the presence or absence of water?

How you convert the measurement into an action; i.e. start/stop the motor?

What does it take to operate (power) the motor?
 
I have seen mainly 2 types of rain sensors.
1) being a float switch style that mounts in your gutter and when enough rain falls into the gutter the float is activated.

2) is a rain monitor which consists of a funnel with a spoon or scoop shaped lever under the funnel, as the spoon fills with water the extra weight makes it tilt down and then empty the spoon, with this action it triggers a reed switch and creates a pulse.
The pulses are counted over a time period to give an indication of how heavy the rain fall is.

So in the first example the pic would time how long the float was activated for.

In the second sensor the pic would count the pulses over time to calculate the measured amount of water by how many pulses there was.

You also need some way of knowing when there has been enough rain to require the engine to be started, this can also be preset as a value in the pic.

Pete.
 
What are the rules? Suppose it only rains 1 drop per 1 square foot a tiny little summer time sprinkle? What about a flash flood or something in between?

You can use a large funnel to catch all the rain is a give area so a tiny sprinlke will be detected.

Is this a 1 time thing or does it have to detect rain each time it rains even if it only rains once a month?

You can use a small spoon to catch 1 drop of water enough weight to tip a tiny balanced mercury switch from N.O. to N.C.
 
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