What is a Raindrop Sensor?

The Raindrop sensors are used for the detection of rain and also for measuring rainfall intensity.  Raindrop sensors can be used for all kinds of weather monitoring.

 

A raindrop sensor is a board on which nickel is coated in the form of lines. It works on the principle of resistance. The raindrop sensor measures the moisture via analog output pins and it provides a digital output when a threshold of moisture exceeds.

 

The module is based on the LM393 op amp. It consists of an electronics module and a printed circuit board that “collects” the rain drops. As raindrops are collected on the circuit board, they create paths of parallel resistance that are measured via the op-amp. It also has a power indicator LED and an adjustable sensitivity through a potentiometer.

Pin Configuration of Rain Drop Sensor

The raindrop control sensor is embedded with an LM393 voltage comparator, and current limiting resistors to adjust signal states and divide the voltage and capacitors as biasing elements.

 

The raindrop sensor control board is usually of the size 3.2cm x 1.4cm. The pin configuration is as detailed below:

 

VCC: This is the positive power supply pin that powers the sensor.

GND: This is the reference potential pin.

D0: This is the digital output pin of the internal comparator circuit.

A0: This is the analog output pin that gives analog signals between 0-5 Volts.

+/-: This is where the rain pad is connected to the LM393.

Raindrop Sensor Features

  1.  The LM393 uses a wide voltage comparator.
  2. The sensor provides both digital and analog output.
  3. It has an output LED indicator.
  4. It is compatible with Arduino.
  5. It is TTL Compatible.
  6. The sensor uses the high-quality FR – 04 double material, a large area of 5.5 * 4.0 CM
  7. Treatment of nickel plating and surface, has fight oxidation, electrical conductivity, and life has more superior performance.
  8. The comparator output, signal clean, good waveform, and driving ability is strong, for more than 15 mA.
  9. It has a potentiometer sensitivity adjustment.
  10. The output format: digital switch output (0 and 1) and analog AO voltage output.
  11. It has a fixed bolt hole, which is convenient for installation.
  12. Adopts high-quality of RF-04 double-sided material.

How to use the Raindrop Sensor

We can interface it with Arduino. To do so we need the following components:

Make the following connections:

  • Raindrop Black Board +ve to the Integrated  Chip +ve
  • Raindrop Black Board –ve to the Integrated Chip –ve
  • Vcc  with  Arduino Board +5V
  • GND with  Arduino Board GND
  • Integrated Chip D0  with Arduino Board Digital pin 2
  • Integrated Chip A0  with  Arduino Board Analog pin A1

Raindrop sensor connected to an Arduino Uno

Raindrop sensor connected to an Arduino Uno

Use the above circuit as a reference for the connections.

Procedure:

  1. Connect the components based on the figure shown in the wiring diagram and the instructions given earlier using pin connectors. The pin number will be based on the actual program code.
  2. After the hardware connection, insert the sample sketch into the Arduino IDE.
  3. Using a USB cable, connect the ports from the Arduino to the computer.
  4. Upload the program.
  5. See the results in the serial monitor

Code:

void setup()

{

// put your setup code here, to run once:

  Serial.begin (9600);

  pinMode (2 , INPUT);

}

void loop()

{

  // put your main code here, to run repeatedly:

  int value = analogRead(A1);

  int digital = digitalRead(2);

  Serial.println (value);

  Serial.println (digital);

  delay(2000);

}

Rain Drop Sensor Working

A raindrop sensor has a board on which nickel is coated in the form of lines. It works on the principle of resistance. The principle is that when there is no rain drop on board, the resistance is high so we get high voltage according to V=IR. When raindrops are present the resistance is reduced as water is a conductor of electricity and its presence connects nickel lines in parallel so the reduced resistance and there is a voltage drop across it.

Copper Pads

The working of the raindrop sensor module is easy and straightforward. The sensor has a series of exposed copper paths that act as variable resistors whose resistance varies according to the amount of water on its surface. Generally, they are not connected but are bridged through the water. This resistance is inversely proportional to the amount of water. The more water on the surface of the rain pads the better the conductivity and this results in lower resistance. The sensor produces an output voltage which is used to determine whether it is raining or not.

Sensor Module

The raindrop sensor module consists of a control sensor and a rain-sensing pad which can be connected to any microcontroller. The module produces an output voltage according to the resistance of the sensing pad and is given at the analog output pin. The same signal is also passed over to the LM393 high-precision comparator to digitize and is made available at the TTL digital output pin.

Control Circuit

In addition, the raindrop module has a potentiometer that is responsible for adjusting the output of the digital pin. This potentiometer is calibrated to receive accurate readings. The potentiometer is connected to the inverting end of the LM393 comparator and sets the reference or threshold voltage meanwhile the input analog voltage is applied to the non-inverting side of the comparator. Then the respective comparator compares both the voltages. This leads to two conditions and gives the output accordingly. If the voltage given as an input is more than the reference voltage then the comparator shows a high state.

Indication LED

Whereas if the threshold voltage is more than the applied voltage then the comparator output will be low. Apart from these, the module has two LEDs, a power LED and a status LED. The power LED will light up when the module is powered and the status LED glows and indicates the digital output pin status.

Applications

The following are a few applications of raindrop sensors:

  • It is used as a water preservation device and this is connected to the irrigation system to shut down the system in the event of rainfall.
  • It is used to support the regular windscreen wiper’s mode and to protect the internal parts of an automobile.
  • This sensor is used in specialized satellite communications aerials for controlling and activating a rain blower over the opening of the aerial feed, to get rid of water droplets from the mylar wrap to keep pressurized as well as dry air within the waveguides.

Conclusion

In this article, we have seen the functions, working, and applications of a Rain Drop Sensor.  We have also seen the procedure to integrate a raindrop sensor and an Arduino UNO.

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