Rain Alarm Circuit using NE555 Timer IC

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Hello friends! Welcome back to ElectroDuino. This blog is based on a Simple Rain Alarm Circuit using NE555 Timer IC. Here we will discuss Introduction to Rain Alarm Circuit, Project Concept, Block Diagram, Components Required, Circuit Diagram, and Working Principle.

Introduction

In the rainy season, when we dry our clothes in the sun, we keep an eye on whether it is raining or not. This is a very boring job and breaks our concentration to do other important work. Otherwise, there are some industries and companies where you have to constantly check whether it is raining outside. That’s why these industries and companies have to deploy a worker to check the outside weather. To resolve these problems, in this project tutorial we will be going to design a Simple Rain alarm circuit, which detects the rainwater and warn us by making a loud Sound. This system makes our life so simple, and also saves our time and money.

Project Concept/Overview

This is a very simple project based on the famous 555 timer IC. The key component of this project circuit the Water Sensor Board, Transistors, 555 Timer IC, Buzzer and LED. Where the water sensor board is used to detect the rainwater that falls on its surface. When rainwater falls on the water sensor, then the rain sensor gives the signal to the base terminal of the transistor. Now the transistor is turned ON and it gives a signal to the 555 timer IC to activate the Buzzer and LED. where the 555 Timer IC is configured in its Astable Mode. The Buzzer and LED are used as an indicator that indicates Rain is falling.

Block Diagram of Simple Rain Alarm Circuit using NE555 Timer IC

Block Diagram of Simple Rain Alarm Circuit using NE555 Timer IC, Introduction to Rain Alarm Circuit, Project Concept, Block Diagram, Components Required, Circuit Diagram, and Working Principle
Block Diagram of Simple Rain Alarm Circuit using NE555 Timer IC

Components Required

Components NameQuantity
NE555 Timer IC (U1)1
BC547 Transistor (Q1)1
2N2222 Transistor (Q2, Q3)2
Water Sensor Board1
220KΩ Resistors(R1)1
330Ω Resistors (R2)4
10KΩ Resistors (R3)1
470KΩ Resistors (R4)1
3.3KΩ Resistors (R5, R6)1
68K ohm Resistors (R7)1
22μF/50V Electrolytic capacitor (C1)1
100μF Electrolytic Capacitor (C2, C4)2
10ηF  Electrolytic capacitor (C3)1
100ρF Ceramic Capacitor (C5)1
Red LED1
12v Buzzer1
Slide Switch (SW1)1
Terminal Block1
12V Power Supply1
PCB board1
Connecting WireAs required in the circuit diagram


Tools Required

Tools NameQuantity
Soldering Iron1
Soldering wire1
Soldering flux1
Soldering stand1
Multimeter1
Desoldering pump1
Wirecutter1

Circuit Diagram Simple Rain Alarm Project using NE555 Timer IC

Circuit Diagram of Simple Rain Alarm Circuit using NE555 Timer IC, Introduction to Rain Alarm Circuit, Project Concept, Block Diagram, Components Required, Circuit Diagram, and Working Principle.
Introduction to Rain Alarm Circuit, Project Concept, Block Diagram, Components Required, Circuit Diagram, and Working Principle.

Working Principle: How the Rain Alarm Circuit Works

When a small amount of rainwater falls on the water sensor board, then the Aluminium Wires on the Water Sensor Board will start conducting and create a close path between points A and B. So the positive supply voltage would get applied on the base of Transistor Q2.
As a result, The Transistor Q2 is turned ON and the current started flowing from the collector terminal to the emitter terminal. The emitter terminal of the transistor Q2 is connected to the base terminal of the transistor Q2 through the Resistor(R3), so the transistor Q1 also turns ON and the Red LED (LED1) starts Glowing.
The emitter terminal of the Transistor Q3 is connected to the Reset Pin (Pin 4) of the 555 Timer IC. Here the timer IC is configured in Astable Mode. So, when this transistor (Q3) reaches the saturation mode then the Reset Pin of the 555 Timer IC gets positive voltage.
Now the timer IC becomes active and It will generate oscillation frequency (Pulse signal) at the output pin (Pin 3). This output will turn ON the buzzer and it starts beeping.
We should note that initially there was no positive voltage at Reset PIN because this pin was connected to the ground through resistance R5 (3.3k). So, the 555 timer IC only works when the Reset pin gets positive voltage.

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