Tell workplace pen thieves and pranksters how you really feel with a barrage of foam darts. This project hacks a Nerf gun to automatically fire at large heat signatures. Simply replace the toy’s trigger system with a servomotor, wire up a home security sensor, add an extended clip, and attach it all to a tripod. Anyone who steps into the sensor’s detection zone gets pelted with darts until they leave—or the clip runs out. Follow these instructions to deter would-be cubicle intruders.
- Nerf N-Strike Elite Stryfe gun (with clip)
- Servomotor with an X-shaped arm
- Single pole single throw (SPST) reed relay
- Passive infrared (PIR) sensor (with 9V battery)
- Roll of 22-gauge hook-up wire
- ¼-inch nut and washer
Phillips-head screwdriver, wire cutters, soldering iron
- Disassemble the Nerf gun with the screwdriver and study the location of the parts inside (see diagram below).
- Remove the electric trigger system, acceleration trigger, jam-clearing door, and one anti-jam feed finger from the muzzle. (You may need a knife.)
- Disable the jam-clearing door’s safety switch by removing the part and reinserting it backward into its slot.
- Solder the PIR to the SPST relay, and the SPST relay to the gun’s acceleration trigger switch (refer to the diagram below).
- Mount the servomotor inside the gun so that its X-shaped servo arm rotates within the dart breech and can push a dart into the rear of the muzzle.
- Solder the servomotor’s negative lead to the gun battery compartment’s negative terminal. Solder the output pole to the acceleration trigger switch.
- Fasten the PIR to the tactical rail on top of the gun and attach the tripod to the heel of the toy’s handgrip with the nut and washer.
- Reassemble the Nerf gun, aim the barrel (and sensor) at the usual point of intrusion, and dare your officemates to cross you again.
- Insert the 9V battery into the PIR first and wait for the servomotor to stop spinning, then load a clip into the Nerf gun.
- Do not use fully loaded clips. Rather, insert only half the required number of darts for each clip capacity (e.g., three darts inside the standard six-dart clip).
- Once activated, the PIR has a refractory period of approximately two to five seconds during which time the sentry will not fire.
- Alignment errors with the servomotor can cause dart jams. Gently tweak your alignment until the darts are fed into the acceleration motor smoothly.
- Dart firing will be rapid and continuous until the PIR sensor no longer detects movement.
Approximate time to build this project: 4 hours
Cost: About $65
WARNING: These instructions will remove important safety features, could ruin the toy, and might even start a foam-dart arms race.
_This article originally appeared in the May 2014 issue of _Popular Science.