Introduction: DIY Rain Alarm Using 555 Timer
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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9 Comments
1 year ago
Can you explain to me how the circuit operation is
6 years ago
Thanks. great little project will give this one a try!!
Reply 6 years ago
Enjoy making..For any help just leave a comment...
Reply 6 years ago
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 :)
Reply 6 years ago
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
6 years ago
Can you give more details about how the rain sensor part in the bottles works please
Reply 6 years ago
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 !!!
6 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?
Reply 6 years ago
You can use the same bottles top and bottom. I used two different bottles.