Introduction: Arduino Controlled Silly String Shooter

Picture of 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

Picture of 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

Picture of Bendy / Twisty

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

Step 4: Mount Servo

Picture of 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!


thomas.kirchner.3760 (author)2014-10-26

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.

Doc_RMK (author)2012-10-16

dude u need to give credit where credit is due!

erickingston (author)Doc_RMK2012-10-17

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 :(

Looks like they borrowed heavily from your instructable there.

Doc_RMK (author)Doc_RMK2012-10-18

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

robertmkmd (author)2013-10-30

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

silmarillion55 (author)2013-10-23

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?

grarged (author)2013-09-21

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.

Mr.Monkey16 (author)2012-10-07

Can I use a Parallax Ping Sensor instead of an IR sensor?

gradof6b (author)2010-11-24

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.

Raccoon81 (author)2010-10-29

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?

erickingston (author)Raccoon812010-10-29

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!

trialex (author)2009-10-29

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?

erickingston (author)trialex2009-10-29

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.


dpapas665 (author)erickingston2010-10-25

Just curious if you ever got that shot of your arduino setup together. Very cool project.

seanturvey (author)2010-10-23

WARNING: Silly string is highly combustible and can be ignited by a lit cigarette.

erickingston (author)seanturvey2010-10-24

Not the stuff i was using, but thanks for the warning.

ly333 (author)2010-10-12

How would I integrate wifi?

erickingston (author)ly3332010-10-13

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!

scraptopower (author)2010-10-06

Great project and outstanding photo's!

How did you get your photos so nice :)

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

zascecs (author)scraptopower2010-10-06

He must of used one of these

erickingston (author)zascecs2010-10-08

Nope, just a big piece of paper and lots of light!

zascecs (author)erickingston2010-10-08

close enough... =P

jaspalmca06 (author)scraptopower2010-10-06


scraptopower (author)jaspalmca062010-10-08

Hi :)

Longchamp (author)2010-10-07

Awesome project. Can this be combined with other projects?

As in, can this thing tweet, take a webcam photo, and fire the silly string all at once when the sensor is tripped?

erickingston (author)Longchamp2010-10-08

Absolutely... Sky is the limit my friend!

Jakeg (author)2010-10-07

Is there any way of doing this without using an Ardunio? I'm kindof interested in crapflinger's idea but I'm not sure if I want to spend the money...

erickingston (author)Jakeg2010-10-08

Sure, just look for silly string shooting toys. You should be able to easily "hack" into them, and hook them up to a cheap motion sensor.

crapflinger (author)2009-10-29

i've got one of These, it's an automated cat scare-the-crap-out-of-er (really effective by the way)....i found that if i take the nozzel off of a can of silly string (or spray paint, or hairspray)...and replace it with this thing...that it actually works pretty well (the silly string doesn't go quite as far because of the nozzel shape)....really great for scaring people

Jakeg (author)crapflinger2010-10-07

Was it the new or the old Ssscat that you have because I'm interested in buying one for this very reason. Is the distance of shooting greatly decreased or is it just by a little bit? I am just wondering if I will have to mod the nossle...


ylpihs (author)2010-10-07

Very nice guide. Will definite try this when Halloween comes.

Computothought (author)2010-10-06

Cool and thanx... Can not wait to adapt that idea for my pc. Already control servos from the parallel port.

siliconghost (author)2009-11-02

What did you use for the IR motion sensor?  That's the once piece I wanted to see but there is no mention of it.  Please add a little more detail!

I used the Sharp IR proximity sensor from

I plan on upgrading to the long range version from

Personman (author)erickingston2009-11-14

 With this PIR sensor at about 1/3 the cost you have an adjustable range of up to about 16-1/2ft.  I'm sure you could rig something up get around the 60 deg beam angle.  I'm giving it a try anyway :) If I'm wrong I'll find another use for it. 

Digi-Key part #269-4710-nd

Apparently I now have to pay to post a link or I would have,  and FYI thats ridiculous.  I could see paying for some features but to post a link?

erickingston (author)Personman2009-11-15

Hey personman,

That's a nice find - I like the price. Take a peek at my post below, and you'll see a link on how to narrow a PIR's detection angle. I picked one up at Radioshack for $10, so I figure the price is about the same as the one you mention after you add shipping.

The part I like about using proximity sensors, is that you can adjust the trigger distance. It's nice, because I can limit the range, letting it only shoot when an object is at a specified distance. So, in this case, we could say only activate when an object is at least 3 feet away, but not more than 8 feet away. Just a little extra control.

Excellent! Thank you! I didn't even know that one existed (and it is very reasonable).

- John

There is one other option, and it's even less expensive. You can use a PIR motion sensor (check your local Radioshack) pointed through a short piece of tubing to make it unidirectional, such as Jonathan did in this instructable:

Whatcha building anyway?

adamw ROX OUT LOUD (author)2009-11-05

i just thought of something - you could widen the hole in the nozzle of the can with a drill to get a shotgun effect.  you know, hit more people. 

tippmannphreak (author)2009-10-31

dude...I'm mad this thing is so cool and NOW I see it...on halloween day... : /

Sweet instructable! I just wish I had seen it about two weeks ago though lol.

5 stars

gmoon (author)2009-10-29

This is too funny--great job! 5 big ones for the rating...

(warning to anyone who's entered in the Halloween contest, and then down-rates someone else's projects--the staff eliminates your negative votes to keep it honest...)

gmoon (author)gmoon2009-10-29

Although I gotta say you should document this in greater detail...

concinos (author)2009-10-29

Very cool, I like how modular the solution is with the spray cap, you can keep changing the can without making new caps. Also this could be used for many other spray automation projects. Plus the pictures are absolutely professional.

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