RapidShark

Nerf RapidStrike CS-18 mod using an Arduino and LiPo battery upgrade to rain foamy annoyance upon one's enemies.

The name originally came from my initial idea to use a pair of NSR Shark 40krpm motors, originally for 12V slot car racing. It quickly became a reference to Randall Munroe's [XKCD comic about lowering one's standards for success as a project wears on...]https://xkcd.com/349/

Versions

This project has undergone a number of major and minor redesigns, and my documentation isn't exactly the best, especially for earlier versions where I assumed this would be a quick hack involving relatively little electronics knowledge (oh, to be 3 years younger and less naive...).

• Mark I

• Completed build

• Used slightly larger motors: 24mm 12V 12850rpm [PAN14EE12AA1]http://www.digikey.com/product-detail/en/PAN14EE12AA1/P14346-ND/2417070

• Covered cut-outs for above with some horribly done epoxy work

• 4S LiPo battery (14.8V nominal)

• Flywheels ran directly off battery voltage

• Rate of fire controlled via diodes (1N5209's?) in series

• Segmented LED display only showed battery voltage.

• Extremely noisy, had jamming issues especially at higher ROF

• Very clumsy controls (giant knob on the side for ROF)

• Overall, kinda crappy prototype

• Mark II

• Never finished build

• Originally going to be 2S LiPo based

• Proved too noisy for reasonable use

• Mark III

• Completed build

• Same [PAN14EE12AA1]http://www.digikey.com/product-detail/en/PAN14EE12AA1/P14346-ND/2417070 as in Mark I

• Used heat gun to deform plastic to accomodate motors

• 4S LiPo battery (14.8V nominal)

• Flywheels again directly off line voltage

• Rate of fire controlled via stupidly big linear regulator (LM335, then LT1083)

• Custom PCB from OSHPark for speed controller

• Actually bothered to paint this one

• Slightly better slide switch for ROF control

• Added pushbutton laser "sight" because reasons

• First attempt at ammo counter using SparkFun Pro Mini 5V to drive a 2 digit segmented display

• Detected shots at first using IR LED & photodiode, but was too noisy so went to reed switch

• Button panel for fiddling with/resetting counter

• Counter was awesome but proved very unreliable in practice

• Noticable voltage drop-out during flywheel spin-up

• Mark IV

• Work in progess

• Skipping paint job to make this one a "sleeper" model

• Motors unselected but will be 130 Mabuchi form-factor to fit in existing case with little modification

• Will feature two proper H-bridges, the [Pololu VNH5019 Motor Driver Carrier]https://www.pololu.com/product/1451

• Since the H-bridges will be electronically controlled, switched to subminiature microswitches hooked up to uC (instead of giant 15A microswitches directly flipping current around)

• [Adafruit Metro Mini]https://www.adafruit.com/products/2590 as main controller

• OLED display (either SparkFun Microview or Ye Olde Generic From Ebay)

• IR interrupter for dart firing detection confirmation, in combination with mechanical position detection for the dart pusher.

• Whole slew of small custom PCB's to aid in wiring

License

• AVR C code (basically, everything under the firmware directory) is licensed under the GPLv2.0.
• Everything else is Creative Commons 4.0, Attribution-Share-Sharealike (CC-4.0-BY-SA)

Acknowledgements

I would not be nearly as far along (or in the ICU from exploding batteries) if not for the help and previous work & knowledge of [torukmakto4]http://torukmakto4.blogspot.co.uk/; read some of the linked posts below for a good breakdown of the basic fire control circuit in the RapidStrike.

I also would like to thank the folks from Blastersmiths UK for their information shared on [Diaries of a Nerf Armorurer]http://nerfarmourer.tumblr.com, as it both provided inspiration, guidance, and a lot of helpful pictures for this project.

References

[The Dart Zone: Wiring and electrical practices]http://torukmakto4.blogspot.co.uk/2013/04/tech-wiring-and-electrical-practices.html [The Dart Zone: Standard Rapidstrike, an Illustrated Guide]http://torukmakto4.blogspot.co.uk/2013/10/standard-rapidstrike-illustrated-guide.html [The Dart Zone: Why compensating for resistance using additional voltage is bad design]http://torukmakto4.blogspot.co.uk/2014/05/why-compensating-for-resistance-using.html [Diaries of a Nerf Armourer: 'Sharked' Rapidstrike CS-18 - Raja and Triakis]http://nerfarmourer.tumblr.com/post/59029888581/sharked-rapidstrike-cs-18-raja-and-triakis [Diaries of a Nerf Armourer: NSR Shark 40 Necrospy]http://nerfarmourer.tumblr.com/post/69776618533/nsr-shark-40-necrospy [Diaries of a Nerf Armourer: Rapidstrike Modification Guide]http://nerfarmourer.tumblr.com/post/57957334515/rapidstrike-modification-guide-also-commissions