Arduino “having11” Guy
Published © GPL3+

Autonomous Nerf Sentry Turret

Use computer vision to control a Nerf gun, aim, and fire, all on its own!

AdvancedFull instructions provided10 hours12,951

Things used in this project

Hardware components

NEMA 17 Stepper Motor
OpenBuilds NEMA 17 Stepper Motor
×1
DFRobot Stepper Motor with Gearbox
×1
DFRobot Stepper Motor Driver
×1
DFRobot Pixy 2 Cam
×1
Arduino Mega 2560 & Genuino Mega 2560
Arduino Mega 2560 & Genuino Mega 2560
×1
Ultrasonic Sensor - HC-SR04 (Generic)
Ultrasonic Sensor - HC-SR04 (Generic)
×1
Nerf Nitron Gun
×1

Software apps and online services

Arduino IDE
Arduino IDE
Fusion 360
Autodesk Fusion 360

Hand tools and fabrication machines

3D Printer (generic)
3D Printer (generic)
Soldering iron (generic)
Soldering iron (generic)
CNC Router

Story

Read more

Custom parts and enclosures

Thingiverse Repository

Schematics

Schematic

Code

Schematic

C/C++
Upload to Arduino Mega
#include <math.h>
#include <Arduino.h>
#include "BasicStepperDriver.h"
#include <Servo.h>
#include <Pixy2I2C.h>

//X is pitch, Y is yaw

const int pins[] = {6,7,8,5,4,12}; //MX STEP, DIR, EN, MY STEP, DIR, EN
const int limit_switch = 26, laser_pin = 11, spool_pin = 10, servo_pin = 13, distance_trig = 29, distance_echo = 30;
double velocity = 21.336;
double velocity_squared = 455.225;
float current_angle = 0.0;
float hyp_distance; //distance from gun to target in meters

#define X_MID 164
#define Y_MID 150
#define DEADZONE 15

#define G 9.8
#define STP_PER_DEG_YAW 3.333
#define STP_PER_DEG_PITCH 184859

#define MICROSTEPS 32
#define RPM 120

#define MOTOR_STEPS_Y 200
#define MOTOR_STEPS_X 1036

//17.7777 steps / degree

BasicStepperDriver pitch_stepper(MOTOR_STEPS_X, pins[1], pins[0]);
BasicStepperDriver yaw_stepper(MOTOR_STEPS_X, pins[4], pins[3]);
Servo trigger;
Pixy2I2C pixy;

enum States {
  ACQUIRE,
  POSITION,
  SPOOL,
  FIRE,
  WIND_DOWN,
  RETURN
};

States state = ACQUIRE;

void setup() {
  Serial.begin(115200);
  init_pins();
  delay(1000);
  //home_pitch();
  pixy.init();
  Serial.println("Ready...");
}

void loop() {
  switch(state){
    case ACQUIRE:
      acquire_target();
      state = POSITION;
      digitalWrite(laser_pin,HIGH);
      break;
    case POSITION:
      Serial.println("positioning");
      position_gun();
      state = SPOOL;
      break;
    case SPOOL:
      Serial.println("spooling");
      digitalWrite(spool_pin,HIGH);
      delay(5000);
      state = FIRE;
      break;
    case FIRE:
      fire_gun();
      state = WIND_DOWN;
      break;
    case WIND_DOWN:
      Serial.println("winding down");
      digitalWrite(spool_pin,LOW);
      delay(2000);
      state = RETURN;
      digitalWrite(laser_pin,LOW);
      state = ACQUIRE;
      break;
  }
}

void fire_gun(){
  Serial.println("Firing gun!");
  trigger.write(108);
  delay(400);
  trigger.write(90);
  delay(2000);
}

void position_gun(){
  float x, y;
  hyp_distance = ping();
  hyp_distance /= 100;
  while(!hyp_distance){   
    hyp_distance = ping();
    hyp_distance /= 100;
  }Serial.println(hyp_distance);
  x = cos(current_angle) * hyp_distance;
  y = sin(current_angle) * hyp_distance;
  float target_angle = get_angle(x,y);
  target_angle /= 100;
  Serial.println(target_angle);
  move_pitch(target_angle - current_angle);
  current_angle = target_angle;
}

void acquire_target(){
  int x=0, y=0;
  long steps_taken=0;
  bool lock = false;
  while(!lock){
    pixy.ccc.getBlocks();
    if(pixy.ccc.numBlocks){
      x = pixy.ccc.blocks[0].m_x;
      y = pixy.ccc.blocks[0].m_y;
      Serial.print("Target seen at location X: ");Serial.print(x);Serial.print(", Y: ");Serial.println(y);
      if(x <= (X_MID - DEADZONE)){ //If too far left, move gun left
        move_yaw(1);
      }
      else if(x >= (X_MID + DEADZONE)){
        move_yaw(-1);
      }
      else if(y <= (Y_MID - DEADZONE)){ //too far up, move gun up
        pitch_stepper.move(33152);
        steps_taken += 33152;
      }
      else if(y >= (Y_MID + DEADZONE)){
        pitch_stepper.move(33152);
        steps_taken += 33152;
      }
      else{
        lock = true;
        Serial.print("Target locked at location X: ");Serial.print(x);Serial.print(", Y: ");Serial.println(y);
        Serial.print("Steps taken: ");Serial.println(steps_taken);
      }
    }
    
  }
  current_angle = steps_taken / STP_PER_DEG_PITCH;
  Serial.print("Current angle: ");Serial.println(current_angle);
}

void init_pins(){
  pinMode(pins[2],OUTPUT);
  pinMode(pins[5],OUTPUT);
  pinMode(limit_switch, INPUT_PULLUP);
  pinMode(laser_pin, OUTPUT);
  pinMode(spool_pin, OUTPUT);
  pinMode(distance_echo, INPUT);
  pinMode(distance_trig, OUTPUT);
  digitalWrite(pins[2],LOW);
  digitalWrite(pins[5],LOW);
  digitalWrite(laser_pin,LOW);
  digitalWrite(spool_pin,LOW);
  trigger.attach(servo_pin);
  pitch_stepper.begin(RPM, MICROSTEPS);
  yaw_stepper.begin(5, MICROSTEPS);
  trigger.write(90);
}

void move_yaw(float degrees){
  yaw_stepper.move(degrees*STP_PER_DEG_YAW*32);
}

void move_pitch(float degrees){
  current_angle += degrees;
  pitch_stepper.move(degrees*STP_PER_DEG_PITCH);
}

float get_angle(float distance, float height){
  float i = 2 * height * 455.225;
  float j = G * distance * distance;
  i += j;
  j = 9.8 * i;
  i = sqrt(pow(velocity_squared,2) - j);
  
  return atan((velocity_squared-i) / (G * distance))*(180/PI);
}

float ping(){
  Serial.println("Getting distance...");
  long duration;
  digitalWrite(distance_trig, LOW);
  delayMicroseconds(5);
  digitalWrite(distance_trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(distance_trig, LOW);
  duration = pulseIn(distance_echo, HIGH);
  return duration / 2 / 29.1; //distance in meters
}

void home_pitch(){
  Serial.println(digitalRead(limit_switch));
  if(!digitalRead(limit_switch)){ //If switch is active
    pitch_stepper.rotate(720);
  }
  while(digitalRead(limit_switch)){
    //Serial.println(digitalRead(limit_switch));
    pitch_stepper.move(-32);
  }
  pitch_stepper.rotate(2880*2);
}

Credits

Arduino “having11” Guy

Arduino “having11” Guy

81 projects • 539 followers
18 year-old IoT and embedded systems enthusiast. Also an intern at Hackster.io who loves working on projects and sharing knowledge.

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