Need a really good prank? How about one that can last for days on end?
while this isn't the best constructed project I've ever built (had to implement it on a pretty quick time line) it's most definitely one of the most fun and evil projects I've built.
So what is it you might ask? Well an air-horn activated by a servo and controlled by arduino of course. YES THERE ARE MANY BETTER WAYS TO DO IT THAN HOW I DID IT, but like I said i was on a tight timeline and pretty much had 1 night to build it and put it in the house i was pranking from when i thought it up. Im also very new to arduino, so if there are any suggestions or better codes or better ways to go about this I'm welcome to suggestions:) this as just a quick and dirty prank.

So how does it work?

I have a frame that holds the air horn in place and the servo right above it. then i programmed the arduino to wait a certain amount of time, rotate the servo to push the air-horn for a quick burst (enough to wake the house up but not let them locate the apparatus), then wait 24 hours and do the same thing again. hopefully it will go for quite a while setting off the air-horn at 4 am every morning. as far as i know the arduino does not have a clock feature, so i guessed about what time i would plug in and hide the unit and told it to wait x hours before setting off the airhorn, then it just loops every 24 hours.

My unit is running off of a power supply, but you could run it off of batteries and get a lot closer to the right time if you want, i was off by about an hour when i set mine up because it took me a while before i could get alone to hide it.

Supplies You'll Need

Air-horn: I got mine at walmart in the party section for about $4
Servo: I already had one, but you can get them on ebay/amazon/localy for anywhere from $3-8
Arduino: should already have one of these but you can get them for around $30

Step 1: Physical Construction

Building the actual unit is pretty straight forward, you just need some kind of box or enclosure to hold everything.
I used an old pretzel tin, but you can really get however creative you want and maybe make it a little more camouflage using an old box or something.

Set the air horn in the corner of the box and secure it ( but make sure the horn is replaceable, if your prankee doesn't find the unit you can just replace the horn and let it keep on going.
Mount the servo above the air-horn in a manner that it can push down the top of the horn.
mount the arduino board somewhere in your box, and attatch the wires.

Heres how I had my servo attatched based on my coding, Red goes to the +5v pin, Black goes to the Gnd pin, and Yellow goes to the Digital pin 9.

Then just plug in whatever power supply your using (wall transformer or battery) and your ready to program!

Step 2: Programming

The coding for this project is very simple, and im sure there are better ways to do it, so if someone wants to take the time to figure something better out and post the code id love to try it out when i get my unit back from pranking, and put it on my ible giving you credit:)

All the code does is tells the Arduino to wait 8 hours, move the servo from 90* to 1* and back, then every 24 hours to move from 90* to 1* and back.

Step 3: Hide Your Prank and Wait

Now just find a good place to hide your prank and hope that whoever your pranking doest smash your Arduino when they find it.
Hopefully it still works for you after you hide it:)