Instructables

Nerf Vulcan Sentry Gun

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In this instructable, I will show you how to modify a Nerf Vulcan to automatically aim and fire at targets.  As an added bonus, this gun won't fire at anyone wearing a shirt with the instructables robot on it. I had this project in mind for a long time and finally managed to find the time to bring it to life.

If you've been browsing through my other instructables, you might have noticed that I am obsessed with Nerf guns. So far, I’ve managed to infect just about everyone around me with the Nerf virus. It is really fun to see how these plastic toys turn grown men into small boys!

My main aim was for it to look awesome; which was difficult to achieve without removing the front part of the gun. But, I managed to accomplish this without removing the barrel, and I’m really happy with how it turned out!

A big thanks goes to Bob who authored an awesome write up on how to build a sentry gun.

Please do not attempt this mod unless you are convinced that you will be able to do it; otherwise you might destroy your gun.

 
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Step 1: Stuff you need

Picture of Stuff you need
05.png
15.png
Stuff you need

To build the base:
  • Wood: 5 mm, 9 mm, 15 mm plywood
  • 20 x 40 x 45 mm and 20 x 40 x 128 mm rectangular block of wood (you can also use the 1.5 mm plywood)
  • Junior drum throne
  • 2 x ball-bearing (12 x 28 x 8 mm)
  • Axial ball bearing (80 x 105 x 19 mm)
  • 12 mm wooden pole
  • Wood glue
  • Sand paper
  • Wood filler
  • Paint/paint brush
  • 15 x spax/wood screws M4 x 40 mm; 4 x screws M4 x 16 mm
  • 4 x wing nuts: M5
  • 4 x machine screws: M5 x 16 mm
  • 4 x brackets
  • Two component glue

Electronics
  • Servo for the turn axis: BMS-660DMG+HS
  • Servo for the tilt axis: Hitec HS-805BB
  • Wire
  • Arduino Uno
  • TIP120 transistor
  • 1N4004 diode
  • 1k resistor
  • Pin header

Other
  • Nerf Vulcan (e.g. here)
  • 6 Volt battery pack
  • 5 kg replacement spring for the Vulcan (e.g. here)
  • Optional: Paint and plastic primer for the gun
  • 3 mm lead pearls or something similar as a counter weight
  • 6V 3700mAh battery pack
  • 9.6V 2000mAh battery pack
  • Webcam
  • Laptop 


Tools
  • Drill (3, 5, 12, 28 (to fit the bearing) mm drill bits)
  • Sander
  • Scroll saw
  • Soldering iron
  • Claw hammer
  • Phillips Head screw driver
  • Hot glue gun

Things like a scroll saw and a powerful drill are useful, but not a 100% necessary. I finished the whole tilt axis with just a fret saw and a cordless drill which was far too weak to drill the 28mm hole (I used the fret saw instead).
racataca7 days ago

What is the working frequency?

Hey! I'm creating this for my last year in university but I'm having some trouble understanding some of the pictures in your guide, I bought my vulcan in the UK and im afraid the internals might be slightly different. I can't figure out where exactly to solder the two wires (the one to the gun servo, and the one to the trigger circuit) because they just look different and the glue in the pics is kinda covering part of the circuit. Could I maybe send you a pic or two of what I did for you to double check? I just don't want it to start puffing smoke when i turn it on lol Any help would be appreciated! And congrats for the guide, and for your painting skills! A warhammer fan maybe?

FWACATA8 months ago
WOW. I WOULD LOVE TO SEE THIS APPLIED TO A PAINTBALL GUN AND MAYBE A COURSE.
Super impressed.

she modified this from an existing paintball project

https://sites.google.com/site/projectsentrygun/home

Squidyman1 month ago

I am curious about the tracking abilities given the webcams very close view range and low resolution as well as poor light/dark contrasting abilities. What is the effective range and ability? About 5 years ago or so I used to play with those guns with my friends and they only reached about 30 feet with a lot of gun arching. Do you have any way to compensate for distance using ultrasonic and gun elevation? I have read about squirt guns that shoot squirrels trying to bird food. Same principles apply here I imagine? Looks like even with all its complexities it is just an arduino, a couple servos, a camera, and a laptop. I might just have to give this a try once I find my guns!

And very cool project btw!

(I used to replace the cap of the nerf bullet with a thumb tack so that is stuck into whatever it landed on (including people) (don't try this XD)).

I've seen other builds of this platform track people at over 30 ft. The important thing is that the webcam doesn't have to focus on an object as much as needed for humans. The software that this platform uses only registers blobs of basic colors (red, green, blue) and does so at a very low resolution to reduce processing (it must process every pixel per frame it processes, usually 10+ frames per second. a single meg pixel would is 1,000,000 pixels). This platform isn't designed to calculate trajectory but can using the same webcam and a cheap laser pointer. Google 'webcam laser range finder'. There good for the 30 ft range, but not much beyond. Check out

http://hackaday.com/2013/06/11/giving-an-rc-tank-a-fire-control-computer/

Hey! Your project was in a Cracked.com article today. Congratulations. Rock on!
BrittLiv (author)  incorrigible packrat11 days ago

Thanks for telling me! It is a really nice write-up.

cr8smthng11 days ago
this is the coolest instructable on the site. I'm definitely making one for "my kids" ;)
jgreat20 days ago

Great tutorial. I'm working on making my own based on your tutorial and others. I have a question about the wiring for the motor. It looks like you are just bypassing the trigger switch with the transistor. So you would still have to use the Nerf battery pack, or wire a battery pack to the existing terminals. Is this correct or am I missing something?

vlre1 month ago

Thanks for all your support Britt! I have put firing base signal from pin 7 and it works marvelously! I am having 5 v out of Pin 7. Pin 10 though does not give me 5V, only 0.43V, so, no result.

As for any other problems...when I put it on the auto movement tracking, and there's nothing moving in front of it, anyway, the program comes up with some square and it goes red out of a sudden, and firing starts! Nothing is moving though!

Tried settings...none...did you have any problems with it?

BrittLiv (author)  vlre26 days ago

Hi, sorry no I didn't. I am not sure what could have gone wrong.

hunter99927 days ago

WOW! 4 medallions at the top! This is such an awesome, detailed 'Ible. Congratz on your win Britt. Thanks for sharing!

vlre2 months ago

Hello. Could you please give some instructions for using and installing the software?

The thing is that link you provided is not working anymore, and I am stuck on this step... everything is ready, all parts altogether...but there's a problem with this software.

Please help. Thank you.

BrittLiv (author)  vlre2 months ago

Where are you stuck? It has been some time since I build it, so I hope that I am still able to help you. You can still find the page I was referring to, here:

https://sites.google.com/site/projectsentrygun/

vlre BrittLiv2 months ago

Hello,

I am stuck with the part where you upload the code to Arduino.

Step 10.

When I try to upload the code, it says

backup as not declared in this scope

sketch_feb07a.ino: In function 'void loop()':
sketch_feb07a:222: error: 'backup' was not declared in this scope
sketch_feb07a:227: error: 'restore' was not declared in this scope

You also have a part of the code named "Backup" but there's no mention where to put that piece...

Tnank you

BrittLiv (author)  vlre1 month ago

Hi, I am sorry I totally missed your comment. You will have to open all three files in the Arduino software in order for it to work (hit ctrl+shift+n to open a new tab).

vlre1 month ago

Everything works no problems!

BUT the gun does not fire.

I checked transistior and the gun itself - no problems.

There's a problem with the code.

Did you change the code from what Bob Rudolph developed?

BrittLiv (author)  vlre1 month ago

Weird, yes, I changed it slightly. Did you use my Arduino code? To which pin did you connect the gun motor and what does the code say?

This has got to be the best automated turret tutorial i have seen for this. i've wanted to put a nerf vulcan on a robot ever since college, and you have achieved it! I am impressed and hoping to use your great work here to create a mobile turret that adds pathfinding algorithms.

Also, I want to try and port the processing scripts over to the raspberry Pi as a substitute for the laptop, for portability and cost reasons.

Thanks for sharing your work here.

-M-

pr3da70r6 months ago
Amazing tutorial!

I'm also wondering, like grozman, if this can be done on a pi instead to eliminate the laptop. Have you had a chance to look into it at all? I'm new to all this so I'm not entirely sure how the firing portion will be doable but besides that, everything else should be straightforward. I have the camera working and I'll be testing the servos when I receive them early next week and then mounting the Vulcan.

If you have any suggestions on readings on how to hook up the wires such that the pi could trigger the Vulcan to fire, I'll appreciate that.

Thanks again for an amazing article. Can't remember the last time I read anything that had be so inspired and impressed.

Pr3da70r,

I have been looking into this. i want to reproduce this substituting the pi for the laptop. there is some way to get Processing to run on the Raspberry Pi.

http://scruss.com/blog/2014/01/07/processing-2-1-o...

Once this is achieved, and the webcam works (or raspi camera module?), the arduino will still be used to work the servos for the turret. Raspi cant source enough current nor can it do a true PWM signal, so you would need an external driver (aka the arduino) in order to control the servos.

I hope to reproduce the turret and port the processing sketch over to the Raspberry pi, hopeully without having to re-code it in Python if processing works successfully.

Best of luck, feel free to pm me for collaboration.

-M-

Kona-chan7 months ago
all hail this gun!

Pew pew pew pew pew

beapilot5 months ago
Hi BrittLiv,

I followed your tutorial with lots of interest and congrats for your win!

I want to build the same project as you but without the servo motors. I will simply use a motor for rotation on 180 degrees. My question is a simple one since i'm a beginner with electronics and specially Arduino.

I've already wired the Nerf gun motor and i wondering how i can easily connect this wire to Arduino in order to trigger fire on/off. So basically i have the orange wire connected to the motor and wonder if with this wire alone i can connect it to Arduino and trigger at a certain condition.

thanks again for this amazing tutorial and sorry for my poor english.

mmokhtar26 months ago
wow thats really cool project , i will remake it with some modifications like installing the gun on moving body , i will make it look like this one i attached

Good luck you are awesome ,,,keep it up ;)
15085_560687273996889_1111700266_n.jpg15085_560687273996889_1111700266_n.jpg15085_560687273996889_1111700266_n.jpg15085_560687273996889_1111700266_n.jpg
danialarbab6 months ago
can u change the logo
u said 'this gun won't fire at anyone wearing a shirt with the instructables robot on it.'
can I change the logo?
BrittLiv (author)  danialarbab6 months ago
Hi, I used a Logitech C525 HD. Yes any logo will work. The robot is already quite complicated. An easier logo will work even better.
Btw. it is an ambitious project, you might want to think about building it with just one axis (just the turning one), to make your life easier. Tell me should you need help.
danialarbab6 months ago
hi britt liv, im doing this for my technology project for school, the webcam you used what was it?
cfree17 months ago
what is the amount of ram you need to run the program as well as video processing to run the program seamlessly and where do i get it
cfree1 cfree17 months ago
i ask this because i would rather get a cheap net-book that is smaller than my huge gaming laptop to do run the program.
You are the goddess of nerf!
BrittLiv (author)  pyromaniac1234567897 months ago
*blush*, wow thanks! My next instructable will be an other Nerf gun project.
zuludaemon8 months ago
Hi Britt, thanks very much for the detailed instructions. I'm getting ready to build a few of these, but I have a question about the axial bearing. It looks like your bearing is not a sealed bearing - is that correct? How much friction can the bearing exert on the system before it is a problem? Presently the BMS-660DMG+HS servos are on backorder, so I will just use the two of the Hitec HS-805BB. Is there any need to specify a low-friction axial bearing, or could i use a lazy susan bearing or some sealed bearing instead? Lazy susan bearings are easily obtainable at stores that specialize in woodworking here in the US. Also, does the panning servo experience any downward force, or is all the force supported by the bearing? Is there a groove that supports your bearing on the lower deck, or does it just sit on the platform? If you could provide a bit more detail on that step it might be helpful. I think that I've got enough info to build this, but a bit more explicit info on the wiring might also help - i.e. how much tolerance is needed on the resistor, etc. Again, thanks very much for this, I'm very excited to do this project!
BrittLiv (author)  zuludaemon7 months ago
Hi, yes the bearing is not sealed. Sorry, I don't know about the friction but considering its size and the small weight of the vulcan I doubt, that you will have a problem.
I am currently using two Hitec HS-805BB and am very happy with the performance.
The downward fore is supported by the bearing (at least how I build it). Remember, that the hitec servo is higher, so you will have to adjust the measurements.
The bearing just sits in the platform.
Sorry, I don't know much about electronics (I am just starting...), so I can't tell you anything about tolerances.
I made a few minor changes to the gun and will probably write an update, but I have 3 other project I would like to finish first.
snoopindaweb8 months ago
Holey Bats.! Take down those mosquitoes.. ~( ;- })={
THIS is why you are considered one of the best on this site!
Spyro2608 months ago
That's awesome!
BrittLiv nice project but can I changed to fire and people that I just want to shoot by Facial scannig
mrrocket68 months ago
Your beautiful and smart ! Wow!
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