is a motion-tracking, telepresent pepperspray machine searching twitter for mentions of anyone getting pepper sprayed at an #OccupyWallSt protest… if an attack is reported it echoes this by spraying anyone in range…


Building your own is SUPER easy thanks to Arduino and Processing. Below are links to the code and the parts. Put them together and BAM you’ve got a motion-tracking pepper spray machine. I based the construction of this around a Graffiti Research Labs design for casing and solenoid-activating spray cans that they have open sourced here.


Searching Twitter:
Thanks to realtime posts from the Occupy Wall St. twitter account, we’re able to get a general sense of when pepper spray attacks might have occurred. Spray It Forward is searching for such instances and if it finds one will spray for about two seconds. For the time being it’s reading the @occupywallst twitter stream using the simple Twitter Search syntax to check for mentions of pepper+OR+pepperspray+OR+arrested+OR+arrest. If the piece were to search for any or all mentions of pepper spray on twitter, this would be too broad and innaccurrate to determine a link to someone actually being sprayed. Restricting the search to the @occupywallst stream increases the chance the mention is linked to a real incident, and also prevents it from reacting to multiple reports of the same instance. I’m currently thinking about the best way to increase the scope of possible inputs while also increasing the 1:1 translation of attack to telepresent spray.  This will likely include a combination of gathering input streams on a wider array of scheduled international protest cities and times and implementing more advanced string parsing.

The Moving Parts
Processing does the twitter searching, then it sends a byte of data to Arduino. The program running on the arduino board is looking for these, if it gets one it will depress the spray can using the solenoid. The motion tracking happens on the arduino side thanks to cheap infrared distance sensors (see part list). There is a servo motor underneath the can turning in the direction of the distance sensor that is reporting the highest value.

You can try the code here.

Arduino board
Motor Shield
Proto Shield (you can use any circuit board or breadboard, you don’t have to use this, same goes for the motor shield, these are just super handy)
Solenoid – you’ll need something like this, but any large-ish one should do. It requires external power at high enough amps to melt your other circuit so don’t mix the solenoid current with the arduino boards
external power relay
2x distance sensors
Servo and base, or you can go the easy route and buy a preassembled rotating platform
a power adaptor strong enough to power your solenoid you will likely need something in the 3amp range
MOUNTING BRACKET AND PIECES – see the excellent design docs the Graffiti Research Labs have posted

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