Rain Alarm Working School Science Exhibition Model, Winning Model for Students (Assembled), 100% Tested


In everyone’s life, water is a basic need but conserving water as well as its proper maintenance is very important. So here is a rain sensor to detect the rain in the agriculture field & generates an alarm whenever there is rain so that we can take some proper actions to conserve the water as well as crops. Consequently, we can enhance the underground water levels through a recharge technique used underwater.

This sensor detects the rain and gives an alert to concerned persons in different fields like irrigation, automobile communication, home automation, etc. This article discusses an overview of a rain sensor and its circuit working.

What is a Rain Sensor?

A sensor that is used to notice the water drops or rainfall is known as a rain sensor. This kind of sensor works like a switch. This sensor includes two parts like sensing pad and a sensor module. Whenever rain falls on the surface of a sensing pad then the sensor module reads the data from the sensor pad to process and convert it into an analog or digital output. So the output generated by this sensor is analog (AO) and digital (DO).


The specifications of rain sensors like different parameters with values are mentioned below.

  • Operating voltage ranges from 3.3 to 5V
  • The operating current is 15 mA
  • The sensing pad size is 5cm x 4 cm with a nickel plate on one face.
  • Comparator chip is LM393
  • Output types are AO (Analog o/p voltage) & DO (Digital switching voltage)
  • The length & width of PCB module 3.2cm x 1.4cm
  • Sensitivity is modifiable through Trimpot
  • Red/Green LED lights indicators for Power & Output

Working Principle

The rain sensor working principle is pretty simple. The sensing pad includes a set of uncovered copper traces which mutually work like a variable resistor or a potentiometer. Here, the sensing pad resistance will be changed based on the amount of water falling on its surface. So, here the resistance is inversely related to the amount of water.

When the water on the sensing pad is more, the conductivity is better & gives less resistance. Similarly, when the water on the surface pad is less, the conductivity is poor & gives high resistance. So the output of this sensor mainly depends on the resistance.

Rain Sensor Pin Configuration

The rain sensor is super easy to use and only has 4 pins to connect.


The rain sensor module includes a sensing pad which includes two series copper tracks coated with nickel. This pad includes two header pins which are connected internally to the copper tracks of the pad. The main function of these two header pins is for connecting the Sensing Pad with the rain sensor module with the help of two jumper wires. Here, the rain sensor module’s one pin provides a +5v power supply toward the one path of the sensing pad, whereas the other pin gets the return power from another path of the pad.

Generally in dry situations, this pad gives huge resistance as well as less conductive. So, the voltage supply cannot be supplied from one path to another path. Here resistance mainly depends on the quantity of water on the sensing pad surface.

Once water falls on the surface of the sensor pad, then its resistance will be reduced & conductivity will be enhanced. So, once the amount of water increases on the surface of the pad then it can supply huge power from one path to other.


At first, the sensing pad has to connect to the sensor module using a jumper wire. Now, both the pins of rain sensor modules like GND & VCC are connected to a 5V power supply pin. After that, fix the threshold voltage at the Non-Inverting terminal of the LM393 IC in the dry state of the pad by turning the knob of the potentiometer to fix the sensitivity of the rain sensor.

the volume of raindrops on the surface of the pad increases then its conductivity increases & resistance decreases. After that from the pad, a less amount of voltage can be provided to the Inverting input terminal of the LM393 IC. Then this IC evaluates this voltage through the threshold voltage. In this state, the input voltage is low as compared to the threshold voltage, as a result, the output of the rain sensor goes LOW.

When no rain falls on the surface of the pad then it has high resistance & less conductivity. After that, the high voltage will be assigned across the pad. Thus, the high voltage from the pad can be provided to the Inverting input of the IC. Once more the integrated circuit evaluates this voltage by using the threshold voltage. So, in this state, this input voltage is higher as compared to the threshold voltage. As a result, the output of the sensor module goes high.


The applications of rain sensors include the following.

These are essential components for the automatic systems used in the agriculture field because rainfall is detected throughout the months of irrigation. These automatically disable the irrigation system while receiving a preferred amount of rainfall & allow this system to restart its fixed conditions once the sensor module gets dried.