Wednesday, January 20, 2016


Here at the office we have a never ending, pretty much daily Nerf Gun War. The battles typically start without much warning when someone fires a shot in your general direction. We have a vast assortment of Nerf Gun and ammo to choose from.

To liven things up a bit some co-workers also bought a thunder pack of smaller Knockoff Nerf Footballs from China. Throughout the day a football will enter your airspace without warning. Thus the need for MAWS

Missile Advanced Warning System

I wanted a way to know when a missile or other large object was incoming to give me time to duck or at least brace for impact. I also wanted a reason to order some PIR sensors for the Arduino. I was the lucky recipient of an Amazon gift card for Christmas so I quickly ordered a pair of sensors.

Hooking the sensors up to the Arduino was a cinch. Basically I just wanted to light up an LED when the sensor noticed movement. The sample code worked perfectly. All I had to do was add another set of variables to control the second sensor. MAWS is outfitted with two PIR sensors for double, that's right double the motion sensing power.


Inital testing indicated that there was little chance MAWS v1 would pick up the Nerf Elite Strike darts. These darts are small and travel fast (especially from the modified Nerf Guns in the office) to be detected by the 2 dollar PIR sensors I purchased.

The NERF Mega darts are also too small to be detected. The MAWS system did pick up a few shots from the Mega darts but the success rate was very low.

Larger projectiles were detected...sometimes.These include Nerf footballs and other various soft projectile type objects.


No fewer than 5 minutes were spent in MAWS construction. This is all prototype so nothing fancy was needed. I grabbed a couple cardboard boxes and a box cutter. Since this was a prototype I decided to just tape together wires with electrical tape to extend the reach of the LEDs.

I taped the LEDs to the top corner of my monitor and ran the MAWS system up to the top of my cube. I moved it back a little so the MAWS system would not pick up my movements for false positives.


The MAWS system is performing at least as well as in the initial testing. I'd say the success rate is about 2.5% just spit-balling. I'd call that a successful project (considering my past projects). I mean imagine if 1000 projectiles are being thrown my way. That is 25 projectiles that are successfully identified before impact...not bad.

It has been a good conversation piece if nothing else. Also it functions well as an advanced warning system if a visitor walks up behind me. So all and all not a bad project.

I imagine if I swing for some more pricey sensors I would have a bit more success.


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