Arduino Controlled Silly String Shooter




This is a fun device that's very simple to make.

I put mine in a pumpkin for Halloween. I also added an IR  motion sensor, sound, and Twitter.
You can follow the victim count on Twitter by following: hackolantern

Step 1: Materials Checklist

Items needed:

- Arduino microcontroller
- A couple cans of Silly String (it's no fun with just one can!)
- Wire coathanger
- Standard sized servo (I used a 39g servo)
- Zip ties
- Basic tools (I'm not going to list everything. You're smart, surely you'll figure it out.)

Step 2: Mark, Measure, and Cut

Take the cap off the Silly String. Measure and mark the cutout locations.

You might be able to use my measurements in the images below, but your brand of Silly String may have different dimensions. Good luck.

Step 3: Bendy / Twisty

Bend your coathanger to resemble the image below. This will act as the trigger.

Step 4: Mount Servo

Run the zip tie through the top holes, and attach the servo.

The trigger should be adjusted to fit YOUR can of Silly String. With my setup, the internal bend is horizontal when the outside lever rests all the way against the servo. This allows for the servo to make a full 90 degree rotation without applying any stress to the other components.

Step 5: Example Code

This code is pretty stupid, but it will give you an idea of how to start.

** I used the SoftwareServo.h library only because the standard servo.h library and the VirtualWire.h library don't get along. If you want to use the standard servo library, it works just fine, but you'll have to whip up your own code (it shouldn't be too hard).

Download the sketch anyway, and take a look.

The other sketches on here, SillStringShooter2.pde and Hackolantern_Tweet.pde, is the actual code I used for my pumpkin. Enjoy!

Runner Up in the
Arduino Contest

Finalist in the
Halloween Contest



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    44 Discussions

    Quite tricky to get the wire to press the spray button in the center. My spray won't shoot a string if you hit it off center, the stuff will just flow out but not shoot.
    So the wire must be mounted slightly off the cap's diagonal to get it to press the button's center. Alternatively it should also work if it is on the diagonal but high enough above the button so that by the time the V-part rotates onto the spray button it's centered on the button.

    This setup should also alleviate the problem of the cap coming off that a previous commenter mentioned.


    6 years ago on Introduction

    dude u need to give credit where credit is due!

    3 replies

    Reply 6 years ago on Introduction

    Wow, I hope he got a good grade! I also hope you're referring to the individual who wrote that report and not me. Look at the dates. I did this project in 2009 and he did his in 2011. That's a bummer he didn't add this instructable as a reference :(


    Reply 6 years ago on Introduction

    You're right! Foot in mouth syndrome! My sincerest apologies. Excellent instructable!


    5 years ago on Introduction

    Can u provide an explanation of the pinouts to the arduino? (which pins r used for what)?

    Great project. I'm a noob at arduino and when trying to load the sketch (shooter2 as I don't want to tweet, etc), I get all sorts of compilation errors and others errors such as 'digitalWrite was not declared, etc? I have the software servo and virtual wire libraries installed. Sorry to bother but can't figure out problem?


    5 years ago

    Great instructable! for those interested, tried the ssscat to shoot silly string, clogged on the first shot. gonna see if I can mod the solenoid valve and nozzle in it to get it to work - I'll post an instructable if so.


    8 years ago on Introduction

    I really want to do this but I'm a total noob and having trouble figuring out how to connect the ir sensor and the servo to the arduino, Help please.


    8 years ago on Introduction

    How do you keep it from pushing the cap off when you have it press the spray nozzle? Getting the shape of the hangar just right to even turn correctly is quite the art, how many attempts on the hangar did it take you?

    1 reply

    Reply 8 years ago on Introduction

    The cap i used had a really snug fit, so i never had a problem with it popping off. I would try to add some paper or something as a shim if the cap is too loose. As for achieving the correct bend in the hanger - it only took minor tweeking. The primary issue I had was simply trying to find a good angle which allowed the arm of the servo to operate the lever correctly. Keep at it, you'll get it!


    9 years ago on Introduction

    Great idea!

    Hope you don't mind some suggestions though.

    You should use the side view showing the mounted servo in a lower-down step, not just in the intro.

    You could also give a brief description of how the arduino is all set up. Which of the three sketches is used in the finished project?

    2 replies

    Reply 9 years ago on Introduction

    Thanks for the input.

    I added the picture of the mounted servo to the final step, and the sketches were described in the code step.

    I'll have to take a snapshot of my Arduino setup. That would be the easiest way to see the configuration.



    Reply 8 years ago on Introduction

    There are two levels of wireless connectivity for this project. Notice the stack of components to the left of the pumpkin? Within that stack is a wifi shield from There are also two very inexpensive RF modules that you can't see. One is inside the pumpkin, and the other is connected to the stack of components on the left. I set it up this way so to avoid ruining my wifi shield with pumpkin goo. Wifi shield costs about $65, and the RF modules only cost $6 combined. So, to answer your question, it's already integrated! Just download the sketch that involves sending tweets, and you can run from there. Have fun!


    8 years ago on Introduction

    Great project and outstanding photo's!

    How did you get your photos so nice :)

    Rated 5* and will vote when the time comes! :)