Why?
Key Goals.
Parts.
Beginning.
Functionality.
Code me up.
Cable tied.
Operations.
Conclusions.

Published August 15, 2017 © GPL3+

Nerf Gun Ammo Counter / Range Finder

Why? Because ammo counters are cool and range finders are also pretty cool and Nerf is cool – mix them together and it's ice cold.

IntermediateFull instructions provided4 hours2,972

Things used in this project

Hardware components

Raspberry Pi Zero

sd card

Resistor 1k ohm

resistor 2k

proximity sensor

Jumper wires (generic)

Male Header 40 Position 1 Row (0.1")

Pi header

Ultrasonic Sensor - HC-SR04 (Generic)

Nerf gun

wire

veroboard

blu-tak

sugru

OpenBuilds Cable Ties (10 Pack)

powerboost

battery

pi zero case

USB-A to Micro-USB Cable

usb hub

Pimoroni Rainbow HAT

Software apps and online services

pibakery

Hand tools and fabrication machines

Soldering iron (generic)

wire cutter

veroboard cutter

Story

Oh yeah.

Why?

Because ammo counters are cool and range finders are also pretty cool and Nerf is cool – mix them together and its ice cold.

I had the idea for this a while back but have only now just decided to build, with the release of the awesome Rainbow Hat from Pimoroni.

This would give me the display needed for the range in CM and a clear display for the ammo counter itself.

Key Goals.

Make a device that can measure distance from the barrel of a Nerf gun.

That can also count down remaining ammo in a clear way.

Make it modular.

Parts.

Rainbow Hat

Raspberry Pi Zero

Resistor Kit

Proximity Sensor

Jumper Wires

Pi Zero Header

Header

Ultrasonic Sensor

NERF N-STRIKE ELITE RETALIATOR

NERF MODULUS RECON MKII BLASTER (Optional)

Wire

Veroboard

Blu-Tak

Sugru

Cable Ties

Powerboost 500

LiPo Battery 1000mAh

Pi Zero Case

Micro USB Cable

Veroboard cutter

SD Card

USB Hub

Beginning.

First its best to wire up the battery and the Powerboost 500, for instructions on this refer to my previous project.

Next job is to solder the Pi Zero 40 pin header onto the Pi itself – see here for an introduction into soldering.

Next you’ll want to put the Pi Zero together with the Case purchased from above, this is pretty simple, you can then put the Rainbow Hat on top.

The hat and the proximity sensor

IMG_20170809_091704

IMG_20170809_094511

Next grab the veroboard, snap the male header from above into 2 parts of nine and solder them into either side of the board as such, with the top resistor being a 1k and the lower one being a 2k, this will attach to the GND pin and form the voltage divider as per the tutorial on modmypi:

Veroboard is nice

You will then want to drill the gap between the resistor in the area marked below so that it will function correctly, using the veroboard cutter listed above:

Once both ends have headers and the resistors are soldered in attach the jumper cables to the sensors and plug the cables into the headers on the side of the resistors making sure that the wires are as such:

Middle pin is unused

Now to save Pins, we will wire GND and VCC to share the same lines on both sensors, solder in wires as such:

Paint skills

While the hat has a number of breakout pins on it it does not have pinouts for GPIO 23 and 24 which are needed for the ultrasonic range sensor as per the above tutorial so I soldered in direct to the pins using this pinout (soldered from the underside is easiest).

The top 4 wires there go to the breakouts on the Rainbow Hat from the Proximity Sensor, the bottom 2 go to the pins direct on the Pi mentioned above:

When all is connected up it should look something like this:

IMG_20170814_192451

IMG_20170814_194207

IMG_20170814_202759

Now go to the awesome PiBakery and configure this and burn to an SD Card:

Everyone should use PiBakery! Everyone.

Hook the Pi up to Ethernet using a USB hub from the parts section with a KB/Mouse put the SD in and power it up!

Once it has configured and rebooted, log in and run through the following tutorials/installations:

Ultrasonic range sensor

Proximity sensor

Now go to your IDE of choice and download the following test scripts:

For the Ultrasonic range sensor

For the proximity sensor

Run the range finder python code and point it somewhere within a few meters:

Nothing went up in smoke!

Now load the proximity sensor test and move the sensor around and it will output the ambient light and distance.

Functionality.

The range finder is simple enough, I want it to run and simply measure the distance in CM from the barrel every couple of seconds or so, nothing complex in the functionality here.

As for the ammo counter, I pondered ways to get it to read the ammo in the magazine dynamically but I could not think of a way to get this done – if someone has an idea for accomplishing this it would be awesome – please let me know if you manage to improve this project.

In lieu of this function I came up with the idea that the ammo per magazine being used should be set manually and then ‘loaded’, as shots are fired this will count down eventually to zero, then when changing magazine the user hits the ‘reload’ button on the hat and the ammo per magazine amount is loaded again.

When manually changing the ammo per magazine by another button on the hat it will show the ammo selection for a second and then return to the current ammo residing in the inserted magazine – there will be a video linked below that will show this clearer.

Code me up.

Now the sensors are checked to be working we can get onto the code for the shot detector (make sure the following scripts go into your home folder):

IMG_20170810_184944

IMG_20170810_184208

Code for the range finder can be found under attachments.

Code for the ammo counter is again under attachments.

Now we need to configure /etc/rc.local to launch the scripts on boot, also found under the attachments of this project.

Save, reboot and watch as the Rainbow Hat lights up!

Cable tied.

Now its time to attach it all to the modulus-compatible barrel of the Retaliator, being that the electronics will be on the barrel only this will mean it can be connected or disconnected to or from any modulus Nerf gun.

I ran cable ties through the tiny slits just below the top rail:

I used blu-tak to hole the PCB, the ultrasonic sensor and the proximity sensor in place (for temporary positioning/testing, Sugru can be used later for a more permanent solution):

The proximity sensor needs to be angled as such so it does not pick up on the proximity of the end of the barrel itself, but will still pick up shots as they leave the barrel.

Wrap the cable ties around the veroboard, the Powerboost, the battery and the Raspberry Pi/Hat assembly itself and pull the ties tight – it is probably best to tighten this one at at a time using hands to hold them in place (4 cable ties were enough to reach around the barrel for each loop):

Now cut off the loose ends of the cable ties and check the stability of the construction and attach to the Nerf gun of choice (mine being the Recon MKII):

1 / 2 • IMG_20170814_211046

IMG_20170814_212350

IMG_20170814_211427

IMG_20170814_212253

Operations.

Here is a YouTube video showing the device in action.

In the video you can see the following:

Me switching the device on and the range sensor eventually measuring the range to the door in the background.

I then set the number of rounds per magazine being used to 2.

I then load the Nerf up and fire off a round and the counter responds accordingly.

I then hit the ‘reload’ button to simulate a new mag with 1 Nerf dart in it.

Next part of the video I switch the device on and show it actively measuring the distance to the door as I get closer / further away from it.

I fire off the 2 darts in the current mag and put in a new mag with 6 rounds, as the default mag size was set to 6 when I hit reload the LED’s reflect this.

I then fire off the remaining 6 rounds and the LED’s count down 1 per shot.

Conclusions.

So it works quite nicely I think and the aesthetic design lands somewhere between Half-Life 2 and Metro Last Light, with some Titanfall sprinkled on.

The next logical step would be to find a way to actively and automatically measure the number of rounds in an inserted magazine and reset accordingly; I am hoping that someone has found or will find a solution to this and improve my design or use this as a jumping point for an entirely better project – please do let me know I would love to see this idea be improved upon as mine is rather, rustic.

Let me know if I’ve missed anything in this guide or if you want some more info and I shall provide it!

#!/usr/bin/env python
#imports
import sys,os
import colorsys
import time

import rainbowhat

import time

import Adafruit_VCNL40xx

vcnl = Adafruit_VCNL40xx.VCNL4010()

#the class used for counting the shots up/down and resetting
class adjustShots(object):
	
	def __init__(self, shotsN):
		self.shotsN = shotsN
	
	def changeAmmo(self, shotsN):
		self.shotsN = shotsN
		return self.shotsN
		
	def showAmmo(self):
		return self.shotsN
	
	def plusShots(self):
		if self.shotsN < 20:
			self.shotsN = self.shotsN + 1
		else:
			self.shotsN = (-0)
		return self.shotsN
		
	def minusShots(self):
		if not self.shotsN < 0:
			self.shotsN = self.shotsN - 1
		return self.shotsN

#here we set the number of shots that are currently in the magazine (0 is -1 here as the counter works by 0 indexing)		
shotsMag = adjustShots(-1)
#here we set the default number of shots per magazine that will be used (as above 11 will count as 12 due to 0 indexing)
shotsPerMag = adjustShots(11)

#display function for the leds
def display_message(message):
    rainbowhat.display.print_str(message)
    rainbowhat.display.show()

#this is the code that handles showing the number of leds at the top, first 7 being red, next 7 orange and final 7 green for a total of-
#21 possible shots, the code here also sets the colour 'below' it for empty shots, so you will see orange shots remaining below green shots etc.
#(check the youtube video linked in the guide on my site for how this works)    
def display_shots(shot_count):
	if shot_count <= 6:
		for x in range(7):
			if x <= shot_count:
				rainbowhat.rainbow.set_pixel(x, 50, 0, 0, brightness=0.1)
				rainbowhat.rainbow.show()
			else:
				rainbowhat.rainbow.set_pixel(x, 0, 0, 0, brightness=0.1)
				rainbowhat.rainbow.show()

	if shot_count > 6 and shot_count < 14:
		for x in range(7):
			shot_count_2 = shot_count - 7
			if x <= shot_count_2:
				rainbowhat.rainbow.set_pixel(x, 200, 50, 0, brightness=0.1)
				rainbowhat.rainbow.show()
			else:
				rainbowhat.rainbow.set_pixel(x, 50, 0, 0, brightness=0.1)
				rainbowhat.rainbow.show()					

	if shot_count > 13:
		for x in range(7):
			shot_count_3 = shot_count - 14
			if x <= shot_count_3:
				rainbowhat.rainbow.set_pixel(x, 0, 50, 0, brightness=0.1)
				rainbowhat.rainbow.show()
			else:
				rainbowhat.rainbow.set_pixel(x, 200, 50, 0, brightness=0.1)
				rainbowhat.rainbow.show()
			
display_shots(shotsMag.showAmmo())

#the 'A' button will cleanly shut the device down
@rainbowhat.touch.A.press()
def press_a(channel):
	os.system("sudo shutdown now")
	pass

#the 'B' button will count the number of shots per mag up +1, looping back around to 1 once it reaches 21
@rainbowhat.touch.B.press()
def press_b(channel):
	shotsPerMag.plusShots()
	display_shots(shotsPerMag.showAmmo())
	time.sleep(1)
	display_shots(shotsMag.showAmmo())
	pass

#the 'C' button initiates a 'reload', so when you put a mag in or reload it will reset the leds to show remaining ammo in the current mag
@rainbowhat.touch.C.press()
def press_c(channel):
	shotsMag.changeAmmo(shotsPerMag.showAmmo())
	print (shotsMag.showAmmo())
	display_shots(shotsMag.showAmmo())
	pass

#loop for detecting proximity - proximity decreasing when a shot passes the sensor indicating a shot and calling the class-
#for the current magazine to minus one shot
try:
	while True:

		proximity = vcnl.read_proximity()

		if proximity > 2540:
			display_shots(shotsMag.minusShots())
			print (shotsMag.showAmmo())
			time.sleep(1)
		
except KeyboardInterrupt:
    pass

#!/usr/bin/env python

#general imports
import time
import colorsys

import rainbowhat

import RPi.GPIO as GPIO
import time

#setup for the GPIO
GPIO.setmode(GPIO.BCM)

TRIG = 23 
ECHO = 24

GPIO.setup(TRIG,GPIO.OUT)
GPIO.setup(ECHO,GPIO.IN)

#loop for measuring distance, this fires out a pulse and measures time to return, it then converts to an int to remove decimals and-
#finally to a string to be sent to the led readout on the lower part of the rainbow hat
try:
    while True:
		
		#print "Distance Measurement In Progress"



		GPIO.output(TRIG, False)
		#print "Waiting For Sensor To Settle"
		time.sleep(2)

		GPIO.output(TRIG, True)
		time.sleep(0.00001)
		GPIO.output(TRIG, False)

		while GPIO.input(ECHO)==0:
		  pulse_start = time.time()

		while GPIO.input(ECHO)==1:
		  pulse_end = time.time()

		pulse_duration = pulse_end - pulse_start

		distance = pulse_duration * 17150

		distance = int(distance)
		
		distance = str(distance)

		print "Distance:",distance,"cm"

		rainbowhat.display.clear()
		rainbowhat.display.print_str(distance)
		rainbowhat.display.show()

		#time.sleep(1)

except KeyboardInterrupt:
    pass

#cleanup code for exiting
rainbowhat.display.clear()
rainbowhat.display.show()

GPIO.cleanup()

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi

sudo python /home/pi/nerfpi.py &
sudo python /home/pi/nerfpi_range.py &

exit 0

Credits

Michael Darby - 314Reactor

56 projects • 146 followers

I like to keep fit, explore and of course make projects.

Nerf Gun Ammo Counter / Range Finder

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Why?

Key Goals.

Parts.

Beginning.

Functionality.

Code me up.

Cable tied.

Operations.

Conclusions.

Code

Ammo Counter Code

Range Finder Code

rc.local

Github

Credits

Michael Darby - 314Reactor

Comments

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Nerf Gun Ammo Counter / Range Finder

Nerf Gun Ammo Counter / Range Finder

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Why?

Key Goals.

Parts.

Beginning.

Functionality.

Code me up.

Cable tied.

Operations.

Conclusions.

Code

Ammo Counter Code

Range Finder Code

rc.local

Github

Credits

Michael Darby - 314Reactor

Comments

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