How to make Rain Alarm Detector at your Home

Here is a simple Rain alarm Detector or Water Drop Detector Alarm Circuit based on a transistor and buzzer pair for sensing the rain. This circuit produces an audible and visible alarm using a buzzer and LED respectively when the rain falls on the sensing plate. This is a useful device and plays an important role in various industries such as irrigation and wireless communication. The main component of this rain alarm circuit is a rain sensor. The sensitivity range of this circuit varies with the change in R1 resistance value. 


Circuit Diagram of Rain Alarm Circuit:

We make a rain alarm detector circuit using a transistor, buzzer, 100Ω and 1K resistor and a LED.

How to make Rain Alarm Circuit   

To connect the all components according to the above circuit diagram.

  1. The positive terminal of 9V power supply is connected with 1K resistance, 100Ω resistance and the positive terminal of the buzzer.
  2. Rain alarm sensor’s one terminal connected with 100Ω resistance and another terminal connected with the base of the NPN transistor.
  3. The emitter of the transistor is grounded and collector is connected in series with the negative terminal of LED and buzzer.
  4. The positive terminal of LED is connected with 1K resistance.

how to make rain alarm circuit

Working Principle of Rain alarm Detector

The main purpose of this rain alarm circuit is to turn on the LED and produce an audible alarm when rain falls on the plate. The rain alarm sensor plate is made up of with mica or Bakelite board having aluminium coating on it. The coating has a distance of 3-5mm between the wire gaps. This construction works on the principle of “Transistor Switch” when we giving voltage at the base terminal the transistor starts the conduction. When we remove the supply from the base of the transistor goes to cut off condition. In normal condition, the sensor is in open circuit. When rain or water drop falls on rain alarm sensing plate the sensor, it will short the points and a voltage would get applied on the base terminal of the transistor, and it will become on. Current starts flowing through the transistor. The LED and buzzer are connected in series with the collector of the transistor. So, when rain or water drop falls on the sensor the buzzer and LED turn on and produces audible and visible alarm respectively. 

The output of Rain alarm Detector:

How to make rain alarm circuit

See tutorial of Rain Alarm Detector:


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