Rain Sensor

 

The rain sensor module is an easy tool for rain detection. It can be used as a switch when raindrop falls through the raining board and also for measuring rainfall intensity. The module features, a rain board and the control board that is separate for more convenience, power indicator LED and an adjustable sensitivity though a potentiometer.

The analog output is used in detection of drops in the amount of rainfall. Connected to 5V power supply, the LED will turn on when induction board has no rain drop, and DO output is high. When dropping a little amount water, DO output is low, the switch indicator will turn on. Brush off the water droplets, and when restored to the initial state, outputs high level.

Working Principle:

This module allows you measure moisture via analog output pins and it provides a digital output when a threshold of moisture is exceeded. The module is based on the LM393 op amp. It includes the electronics module and a printed circuit board (control board) that “collects” the rain drops. As rain drops are collected on the circuit board, they create paths of parallel resistance that are measured via the op amp. The lower the resistance (or the more water), the lower the voltage output. Conversely, the less water, the greater the output voltage on the analog pin. A completely dry board for example will cause the module to output five volts.

Additional info:

Rain sensor can also be used as an alternative of water sensor but the sensitivity will be more.

 

Features :

  1. Operating voltage: 5V
  2. Provide both digitaland analog output
  3. Adjustable sensitivity
  4. Output LEDindicator
  5. Compatible with Arduino
  6. TTLCompatible

 

Specification :

  1. Adopts high quality of RF-04 double sided material.
  2. Area: 5cm x 4cm nickel plate on side
  3. Anti-oxidation, anti-conductivity, with long use time
  4. Comparator output signal clean waveform is good, driving ability, over 15mA
  5. Potentiometer adjust the sensitivity
  6. Working voltage 5V
  7. Output format: Digital switching output (0 and 1) and analog voltage output AO
  8. with bolt holes for easy installation
  9. Small board PCB size: 3.2cm x 1.4cm
  10. Uses a wide voltage LM393 comparator

Link to datasheet:

https://www.openhacks.com/uploadsproductos/rain_sensor_module.pdf

Do’s:

  1. Always take sensor from sides only.
  2. Read the specifications before using any sensor.

Don’t’s:

  1. Don’t laid the sensor to be freezed.
  2. Don’t apply voltage on wrong pins.

 

Storing Instructions:

It must be stored in thermocol or in a box with care, so that static energy does not damage the components of sensor.

 

Advantages

  1. It helps in saving money by switching off the irrigation system when it rains. This saves money by cutting off bills on electricity consumption. 
  2. Operating principle is very easy. 
  3. Rain sensors help save water during rain events and hence water is available during summer and emergency applications such as firefighting etc. 
  4. Installation of rain sensor based systems are very much simple.
  5. Individual rain sensor costs very less.

Disadvantages

  1. The rain sensor based system functions when water falls on the sensor directly. 
  2. The cost of overall system increases as additional components are needed along with rain sensor.
  3. In order to avoid false detection of rain, it requires rain sensors to take decision after few minutes.

Schematics

Interfacing with Arduino:

Arduino Code:

int Sensor = 2; 

int Led    = 13;

void setup()

{

 pinMode(Led, OUTPUT);

 pinMode(Sensor, INPUT);

 Serial.begin(9600);

 }

void loop()

{

 int temp = digitalRead(Sensor);

 if (temp == LOW)

 {

   digitalWrite(Led, HIGH);

   Serial.println(“It’s Raining”);

 }

 else

 {

   digitalWrite(Led, LOW);

   Serial.println(“Not Raining”);

 }

}

Applications:

  1. Irrigation System
  2. Automotive System

FAQ’s:

Q1. How long does it take for the rain sensor to dry out?

Ans. Dry out time could be as little as 4 hours, depending upon weather conditions (temperature and humidity) and how the vent ring is set. If the weather remains cold and damp, your sensor could be active for months.

 

Q2. Can I save money by installing my own system?

Ans. No. In fact in many cases, you’ll spend more. It is primarily focused on the irrigation system.

 

 

 

Reference:

 

http://www.instructables.com/howto/rain+sensor/

https://circuitdigest.com/electronic-circuits/rain-alarm-project

https://www.electronicshub.org/rain-alarm-project/ https://www.bluejayirrigation.com/faq

https://www.hunterindustries.com/en-metric/homeowners/product-support/sensors

https://en.wikipedia.org/wiki/Rain_sensor

http://www.rfwireless-world.com/Terminology/Advantages-and-Disadvantages-of-Rain-Sensor.html

https://wiki.eprolabs.com/index.php?title=Raindrop_Sensor

https://www.openhacks.com/uploadsproductos/rain_sensor_module.pdf

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