Hi and welcome to my very first instructable.

For my course , we had to create something revolving around the theme of digital streetart. The only requirements were that we had to work with an arduino.

For this project I created a prototype of a paintball printer. For this I wrote a little program which can convert small or (big) images into a series of points for the paintball sentry gun to fire, printing out the image on the wall. The street art angle is that the images are converted to a type of stencil.

Step 1: Gathering All the Parts

For this project you need several parts. I divided them here into 3 categories.

Electronics:

Arduino Uno ( or any other arduino)
3 Three standard servo's (no continuous rotation)
- Two reasonably strong model servo's. I used the modelcraft RC-car servo 4519 bb (http://www.servodatabase.com/servo/modelcraft/4519-bb) for the tilt and pan.
- And a tiny one for the trigger. I used the standard one that comes with the arduino starter kit for this. http://arduino.cc/en/Main/ArduinoStarterKit
Three capacitors, also the ones provided with the arduino starter kit. I used the 100µF ones.( http://arduino.cc/documents/datasheets/cap100uF.pdf )
Couple of jumper wires
A green and red LED.
A couple of resistors ( I used 2.2k Ohms)

Hardware

Couple of MDF sheets. I used 4mm thick ones for the base and the gears.
Some woodscrews
Some bolts and nuts ( needed to make the base for the gun)
Paintball gun. I used a tipmann model (see picture)
Laptop/ pc to run the software of course

Step 2: The Software

For this project I used processing in combination with the arduino code.

I used serial communication to send the converted values of the converted images to the arduino.

First I calculated the number of white dots. I do this by scanning the pixels of an image and comparing the brightness of each pixel with a threshold. If the brightness is higher than the threshold, I make that pixel a white dot. I extrapolated and saved the x and y coordinates to an array and I send this array with serial to the arduino. The arduino then converts these x values to pan and tilt values and sets the corresponding servo's in the right position, moving the gun to the correct location. Once an x and y value are successfully placed, the trigger servo triggers and so on.

Below are my processing sketch and my arduino code. (There still are a lot places the code can be improved but It seemed fine for me).

The software only works for images which are 15 x 15 for now.

Step 3: The Base for the Gun

For the gun we need to build a base.

For the pan unit I lasercut some gears out of some sheets of MDF (4mm thick) and attached the pan servo like this

(INSERT PICTURE HERE)

The pdf for the lasercut I used is attached.

For the tilt part of the base I used a piece of plywood 8.5cm wide and 42 cm high. I drilled a hole into the piece and fitted the tilt servo in like shown in the picture

I would suggest you would check http://projectsentrygun.rudolphlabs.com/make-your-own for a better guide.