# Lesson 14 Rain Detection

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Introduction

The rain detection module detects rain on the board. Place the rain detection board in the open air. When it is raining, the rain detection module will sense the raindrops and send signals to the Raspberry Pi.

Components

– 1 * Raspberry Pi

– 1 * Breadboard

– 1 * Network cable (or USB wireless network adapter)

– 1 * Rain Detection module

– 1 * PCF8591

– 1 * LM393

– 1 * 2-Pin ribbon cable

– 1 * 4-Pin anti-reverse cable

– Several jumper wires (M to F)

– 1 * Glass of water (Self provided)

Experimental Principle

There are two metal wires that are close to each other but do not cross on the rain detection board. When rain drops on the board, the two metal wires will conduct, thus there is a voltage between the two metal wires. The schematic diagram is as shown below:

Experimental Procedures

Step 1: Build the circuit

Note:The two pins on the rain detection board are exactly the same. You can connect them to pin IN and GND on LM393.

For C language users:

Step 2: Change directory

cd /home/pi/SunFounder_SensorKit_for_RPi2/C/14_rain_detector/

Step 3: Compile

gcc rain_detector.c –lwiringPi

Step 4: Run

sudo ./a.out

For Python users:

Step 2: Change directory

cd /home/pi/SunFounder_SensorKit_for_RPi2/Python/

Step 3: Run

sudo python 14_rain_detector.py

Now dip some water onto the rain detection board until “raining” display on the screen. You can adjust the potentiometer on LM393 to detect the threshold of rainfall.

C Code

``````#include <stdio.h>
#include <wiringPi.h>
#include <pcf8591.h>
#include <math.h>

#define		PCF     120
#define		DOpin	0

void Print(int x)
{
switch(x)
{
case 1:
printf("\n***************\n"  );
printf(  "* Not Raining *\n"  );
printf(  "***************\n\n");
break;
case 0:
printf("\n*************\n"  );
printf(  "* Raining!! *\n"  );
printf(  "*************\n\n");
break;
default:
printf("\n**********************\n"  );
printf(  "* Print value error. *\n"  );
printf(  "**********************\n\n");
break;
}
}

int main()
{
int analogVal;
int tmp, status;

if(wiringPiSetup() == -1){
printf("setup wiringPi failed !");
return 1;
}
// Setup pcf8591 on base pin 120, and address 0x48
pcf8591Setup(PCF, 0x48);

pinMode(DOpin, INPUT);

status = 0;
while(1) // loop forever
{
analogVal = analogRead(PCF + 0);
printf("%d\n", analogVal);

if (tmp != status)
{
Print(tmp);
status = tmp;
}

delay (200);
}
return 0;
}``````

Python Code

``````#!/usr/bin/env python
import PCF8591 as ADC
import RPi.GPIO as GPIO
import time
import math

DO = 17
GPIO.setmode(GPIO.BCM)

def setup():
GPIO.setup(DO, GPIO.IN)

def Print(x):
if x == 1:
print ''
print '   ***************'
print '   * Not raining *'
print '   ***************'
print ''
if x == 0:
print ''
print '   *************'
print '   * Raining!! *'
print '   *************'
print ''

def loop():
status = 1
while True:

tmp = GPIO.input(DO);
if tmp != status:
Print(tmp)
status = tmp

time.sleep(0.2)

if __name__ == '__main__':
try:
setup()
loop()
except KeyboardInterrupt:
pass
``````