Picture of Rain Detector
Make a rain detector with a few household items. A great project for the kids!
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Step 1: Gather Materials

You will need a cup, a 9 volt battery, two paperclips, electrical tape, some wire, a light, and some salt. The only tools needed are a pair of wire cutters and some wire strippers.

Step 2: Put it all together

Picture of Put it all together
Bend the paperclips straight. Then put them along the sides of the cup so that they are touching the bottom, bend the excess over the edge of the cup. You may have to tape the paperclips to the cup so that they stay. Next, take a length of wire and strip off the ends. Attach one end to a paperclip and the other end to a battery terminal. Then take another length of wire and strip the ends off. Attach one end to the second paperclip and the other end to the light. I chose to use an LED, but it can be any small light. If you use an LED, make sure you get the polarity correct so it will work. Lastly, take another piece of wire, strip the ends, and run it from the light to the battery. Use tape to fasten all of the connections.

Step 3: Test It!

Picture of Test It!
Sprinkle some salt in the bottom of the cup. This will improve the conductivity of the water. Then put a small amount of water in the cup, just enough to cover the bottom. That should complete the circuit and the light should turn on. If not, then go back and check the connections. Once it works, you can extend the wires and run the cup outside and have yourself a handy little rain detector.
nanda.prian.93 months ago

nice idea! Thanks for this idea I won at my innovation competition.


beehard445 years ago
good if you want to detect rain 3 minutes after the first drops but what if you want to detect the first drops?
check my one it works on the first drop
shaheer322 years ago
there is another way of doing this
1. get a base with 3 stands
2. attach a tissue to a clip
3. add a metal to the clip
4. put it all on the base and tape the unattached end of the tissue to the first stand
5. make a wire to a light bulb
6. cut the + terminal of the wire into half
7. put it on the stand so if the metal falls it will complete the circuit
8. put the battery and it works!

the tissue paper breaks by water causing the circuit to be complete
yrajput3 years ago
SAUL U R THE BEST DUDE!!!!!!!!!!!!!!!!!!!!!!!!!!!!

yrajput3 years ago
Really I am passing this comment at night at 11 o clock tommorow is my science exhibition ,you came like god 2 me INSTRUCTIBLES ROCK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

itz a gud model.............. bla bla
could u also use baking soda?
can i use melted aluminum?
hmm... maybe if i replace the light with a relay to trigger something...
arcticfox6 years ago
This is brilliant. Instead of light, it can be a buzzer or even a motor to close your windows etc.
what type of buzzer can i use
Better civil servant with a transistor
mamai7 years ago
what is the use of salt? does it really detect wqhen the rain comes?
cool post. Actually, the salt can be omitted in most cases. LEDs don't need a lot of current. I remember making a salt switch back in grade school (when LED's where still rare). It was pretty much the same as this except it used a big ol' incandescent flashlight bulb and D cell batteries. When you were using those big clunky bulbs (they needed huge current!)you had to put in the salt or it wouldn't work at all. And, the batteries were drained quite quickly. Thanks for the post!
Rokko8652 mamai7 years ago
It says it helps the conductivity of the water
jazeleh7 years ago
hi im new here.....just want to ask.....ammm what is the use of the salt and the paper clip? please.....
radiorental9 years ago
Nice idea generator, a buzzer wuld be more fun. Kids will ask what is the point of a light if you can just stick your hand out to feel the rain. Some suggested improvements would be good such as an array made from a proto/bread board (the type with the ling of copper on the board ready for solder) or adding in salt to make conductivity better very cool hook in to circuitry
instead of a light.....use a REALLY loud alarm...lmao
WolvesOfWar9 years ago
nice idea for other projects simular. like an alarm.
power9 years ago
nice invention i wouldn't thought of doing it myself
latobada9 years ago
nice, i did this with a fountain, and a buzzer after a certain water level so it could be re-filled. this one is nice for kids though, i doubt they would be paitient enough to try it once it rains, but a good activity if it is raining!
jtobako9 years ago
i think a grid across the bottom or a cup with a pointed bottom would be a better detector. the way this is set up it would have to be raining for a while for this to detect it.
jason3659 years ago
It would be really fun to add an array of inputs and thereby measure the depth of the water. Then you could send the info to your computer. Of course you would need to secure your cup if you were going to keep it outside.
ericcherry9 years ago
I had been toying with the idea of making such a thing for under my sink. I'm a bachelor and honestly don't spend much time in my kitchen, it'd be to the point of -too late- by the time I noticed that the sink had a slow link. A little LED hanging from the cupboard by the baseboards could save me some bucks. Clever!