DIY Rain Alarm Using 555 Timer




Introduction: DIY Rain Alarm Using 555 Timer

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Building a home made rain alarm.

This circuit beeps for about 40 seconds when it detects rain. This circuit uses a 555 timer.

This circuit can also be used with pressure sensor or with LDR for detecting light

Step 1: Things Required

1. 330 Ohm Resistor

2. 1M Ohm Resistor - 3

3. 330k Ohm Resistor - 3

4. 10k Ohm Resistor

5. 100uF / 25 Volt Capacitor

6. 0.1uF Ceramic Capacitor

7. 0.01uF Ceramic Capacitor

8. LED

9. 555 Timer

10 Buzzer

11. BC177

12. 2 pin connector male & female

13. PCB Board, Wires& Battery

14. Plastic Bottles - 2

15. Soldering Rod, Soldering Wire & Soldering Paste

16. Insulation Tape, Scissor & Hot Glue Gun

Step 2: Making Video

You can watch the making of the DIY Rain alarm or continue reading the post on how to make the DIY rain alarm

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Step 3: Circuit Diagram

Step 4: Circuit Construction

Mount all the components on the PCB boards and connect the circuit according to the circuit diagram as shown in the previous step.

Step 5: Rain Switch Making

1. To make the rain switch we need two bottles.

2. Cut them as shown in the 1st and 2nd image

3. Make two holes in the sides of the cap to insert the wires

4. Now insert the wires and secure them with hot glue. Note : make sure the ends of the wire are exposed and the two wires does not come in contact with each other

Step 6: Finished Images

To watch the testing video CLICK HERE

Testing begins @ 8:58


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555 Timer :

Buzzer :

Resistors, Capacitors & Others Things :

PCB Board Connectors -


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Wires -

Battery -

PCB Board -

Insulation Tape -

Scissor -

Hot Glue Gun -

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555 Timer :

Buzzer :

Resistors, Capacitors & Others Things :

PCB Board Connectors -


3.5 mm Jack -

Soldering Kit -

Wires -

Battery -

PCB Board -

Insulation Tape -

Scissor -

Hot Glue Gun -


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    8 Discussions

    Thanks. great little project will give this one a try!!

    3 replies

    Enjoy making..For any help just leave a comment...

    Hello, thank you for an interesting idea, I was trying to figure out the circuit, and I still can't seem to understand why the pnp transistor is wired that way... Every tutorial in the web points that emitter (marked with an arrow) should be connected to Vcc, while here it is grounded. Can you please provide some insight on this? Thank you very much :)

    Hello, The emitter is grounded because it is a common emitter circuit, which means the emitter is common for both input & the output & Common emitter has very high gain

    The reason for using common emitter is, to amplify the faint signals received by the rain sensor.

    Hope my answer helps you


    2 years ago

    Can you give more details about how the rain sensor part in the bottles works please

    1 reply

    The two wires in the rain sensor are not connected which means the circuit is in open loop state. Since we know water conducts electricity. So, when the water gets collected in the cap the wire gets connected through water as the medium and circuit becomes closed loop and triggers the alarm..

    Hope this answer helps you !!!


    2 years ago

    In image 2 have you finished cutting the second bottle? I cannot tell from the photo, but it looks like it is inverted with the threaded portion removed to accept the inverted portion of the first bottle?

    1 reply

    You can use the same bottles top and bottom. I used two different bottles.