LEGO Mindstorms NXT Laser Guided Shooter

October 21, 2010 LEGO Mindstorms, Mindstorms NXT Robots, Other Hardware, LEGO Mindstorms Hardware, LASER Sensor No comments

I’ve been busy playing with my LASER Sensors , and have put together a Zamor powered LEGO Mindstorms NXT Laser Guided Shooter. If you would like to build your own, I have included the Model Instructions and NXC Program Code.

For this particular version of my LEGO Mindstorms NXT Laser Guided Shooter, I’ve been trialling an 5mW 780nm Infra-red LASER. Thus far all tests have proved very reliable up to around 2 metres. The biggest issue is the fact you can’t see the LASER Beam with the naked eye, which makes alignment rather tricky. To get around this I’ve been using my old Sony DCR-TRV18E MiniDV Camera’s Night Vision & USB streaming capabilities to see the position of the LASER. This method works very well and is only needed for the initial alignment of the LASER Sensor on the Robot, so the Beam runs parallel with the Robot’s Base.

LDraw Model of the LEGO Mindstorms NXT Laser Guided Shooter

The 780nm Infra-red LASER works on par with the standard Red LASER modules I have been using. I would really like to source some Green or Blue LASER modules that are smaller enough to replace the standard Red modules I currently use. Either the Green or Blue LASER modules should increase the detection range as they are outside the normal ambient light pollution levels you need to over come for greater detection distances above 2 metres.

Assembled LEGO Mindstorms NXT Laser Guided Shooter

My standard Red LASER Sensors are reliable below 2 metres, but above, external light sources can make the detection erratic. The difference between natural, florescent and incandescent light source is like chalk and cheese. I find that florescent lighting, which tends towards the blue end of the visible spectrum gives by far the best results.

You Can also build it as a Ultrasonic Guided Shooter
(If you down have one of my LASER Sensors)

View Laser Guided Shooter NXC Code:

/* ============================================================================

                         LEGO Mindstorms NXT                          
                      &lt;= Laser Guided Shooter =&gt;
                            September 2011
                          www.rjmcnamara.com

============================================================================ */


#define FIRE            OUT_
#define TURRET          OUT_C
#define TURRET_PORT     S1
#define TRIGGER_PORT    S2
#define LASER_PORT      S4
#define TURRET_HOME     SENSOR_1
#define TRIGGER         SENSOR_2
#define LASER           SENSOR_4
#define SCAN_SPEED      75
#define CENTER_TURRET   11.5*360
#define ANGLE           MotorRotationCount(TURRET)
#define CENTER          2 * 360  // Degrees
#define SWEEP           9 * 360 // Degrees
#define AMBIENT_MARGIN  0

int target, max;
int ambient, level;

/* ============================================================================

         &lt;= Display Laser Sensor Level =&gt;

============================================================================ */

task LaserReading()
{
 while (true)
  {
     TextOut(0, LCD_LINE3, "Ambient            ");
     NumOut(50, LCD_LINE3, ambient);
     TextOut(0, LCD_LINE4, "Reading            ");
     NumOut(50, LCD_LINE4, level);
     if (level &gt; ambient)  // Object Found
       {
         RotateMotor(FIRE, 100, 360);
         PlayFile("TargetFound.rso"); // Audible "Target Found!"
         while (SoundFlags() != SOUND_FLAGS_IDLE);
         NumOut(50, LCD_LINE4, level);
         TextOut(0, LCD_LINE2, "Target Found            ");
         PlayFile("Fireing.rso"); // Audible "Target Found!"
         while (SoundFlags() != SOUND_FLAGS_IDLE);
       }
         else
           {
             TextOut(0, LCD_LINE2, "No Target Found            ");
           }
     Wait(50);
   }
}


/* ============================================================================

         &lt;= Align Robot's Turret =&gt;

============================================================================ */

void align() {
  while (TURRET_HOME != 1)
		{
      OnFwd(TURRET, 100);
		}
  RotateMotor(TURRET, -100, CENTER_TURRET);
	Off(TURRET);

  while (TRIGGER != 1)
		{
      OnFwd(FIRE, 20);
		}
  Off(FIRE);
  ResetAllTachoCounts(TURRET);
}



/* ============================================================================

         &lt;= Rotate Robot's Turret =&gt;

============================================================================ */

task measureSweep() {
  RotateMotor(TURRET, 100, CENTER+SWEEP);
}



/* ============================================================================

         &lt;= Measur Ambient Light Level =&gt;

============================================================================ */

void measure_light() {
  ambient = 0;
  start measureSweep;
  while (MotorRunState(TURRET) == OUT_RUNSTATE_RUNNING) {
    level = LASER;
    if (level &gt; ambient) ambient = level;
  }
  ambient += AMBIENT_MARGIN;
  TextOut(0, LCD_LINE6, "Ambient            ");
  NumOut(50, LCD_LINE6, ambient);
}



/* ============================================================================

         &lt;= Check for Target =&gt;

============================================================================ */

void check() {
  level = LASER;
  if (level &gt; max) {
    target = ANGLE;
    max = level;

  }
}



/* ============================================================================

         &lt;= Scan Robot's Turret =&gt;

============================================================================ */

void scan() {
  max = 0;
  if (ANGLE &gt; CENTER) {
    // look left
//    OnRevReg(TURRET, SCAN_SPEED, OUT_REGMODE_SPEED);
    OnRev(TURRET, SCAN_SPEED);
    while (ANGLE &gt; CENTER-SWEEP)
      check();
  }
  else {
    // look right
//    OnFwdReg(TURRET, SCAN_SPEED, OUT_REGMODE_SPEED);
    OnFwd(TURRET, SCAN_SPEED);
    while (ANGLE &lt; CENTER+SWEEP)
      check();
  }
  Off(TURRET);
}



/* ============================================================================

         &lt;= Turn Laser Off =&gt;

============================================================================ */

void SetSensorLightInactive(const int port) {
  SetSensorType(port, SENSOR_TYPE_LIGHT_INACTIVE);
  SetSensorMode(port, SENSOR_MODE_PERCENT);
  ResetSensor(port);
  PlayFile("LaserOff.rso"); // Audible "Laser is Off!"
  while (SoundFlags() != SOUND_FLAGS_IDLE);
}



/* ============================================================================

         &lt;= Turn Laser On =&gt;

============================================================================ */

void SetSensorLightActive(const int port) {
  SetSensorType(port, SENSOR_TYPE_LIGHT_ACTIVE);
  SetSensorMode(port, SENSOR_MODE_PERCENT);
  ResetSensor(port);
  
  PlayFile("LaserOn.rso"); // Audible "Laser is On!"
  while (SoundFlags() != SOUND_FLAGS_IDLE);
  Wait(250);
  PlayFile("LaserOn.rso"); // Audible "Laser is On!"
  while (SoundFlags() != SOUND_FLAGS_IDLE);
  Wait(250);
}



/* ============================================================================
===============================================================================

         &lt;= Main Robot Control =&gt;

===============================================================================
============================================================================ */

task main() {
  ClearScreen();

  SetSensorLightInactive(LASER_PORT);
  PlayFile("LaserOff.rso"); // Audible "Laser is Off!"
  while (SoundFlags() != SOUND_FLAGS_IDLE);
  
  start LaserReading;
  SetSensorTouch(TURRET_PORT);
  SetSensorMode(TURRET_PORT, IN_MODE_BOOLEAN);
  SetSensorTouch(TRIGGER_PORT);
  SetSensorMode(TRIGGER_PORT, IN_MODE_BOOLEAN);
  Wait(250);

  PlayFile("Aligning.rso"); // Audible "Aligning!"
  while (SoundFlags() != SOUND_FLAGS_IDLE);

  align();

  measure_light();

  SetSensorLightActive(LASER_PORT);

  PlayFile("SanningForTarge.rso"); // Audible "SanningForTarget!"
  while (SoundFlags() != SOUND_FLAGS_IDLE);
  while (true) {
    scan();
  }
  StopAllTasks();
}

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/* ============================================================================

LEGO Mindstorms NXT

<= Laser Guided Shooter =>

September 2011

www.rjmcnamara.com

============================================================================ */

#define FIRE OUT_

#define TURRET OUT_C

#define TURRET_PORT S1

#define TRIGGER_PORT S2

#define LASER_PORT S4

#define TURRET_HOME SENSOR_1

#define TRIGGER SENSOR_2

#define LASER SENSOR_4

#define SCAN_SPEED 75

#define CENTER_TURRET 11.5*360

#define ANGLE MotorRotationCount(TURRET)

#define CENTER 2 * 360 // Degrees

#define SWEEP 9 * 360 // Degrees

#define AMBIENT_MARGIN 0

int target, max;

int ambient, level;

/* ============================================================================

<= Display Laser Sensor Level =>

============================================================================ */

task LaserReading()

{

while (true)

{

TextOut(0, LCD_LINE3, "Ambient ");

NumOut(50, LCD_LINE3, ambient);

TextOut(0, LCD_LINE4, "Reading ");

NumOut(50, LCD_LINE4, level);

if (level > ambient) // Object Found

{

RotateMotor(FIRE, 100, 360);

PlayFile("TargetFound.rso"); // Audible "Target Found!"

while (SoundFlags() != SOUND_FLAGS_IDLE);

NumOut(50, LCD_LINE4, level);

TextOut(0, LCD_LINE2, "Target Found ");

PlayFile("Fireing.rso"); // Audible "Target Found!"

while (SoundFlags() != SOUND_FLAGS_IDLE);

}

else

{

TextOut(0, LCD_LINE2, "No Target Found ");

}

Wait(50);

}

/* ============================================================================

<= Align Robot's Turret =>

============================================================================ */

void align() {

while (TURRET_HOME != 1)

{

OnFwd(TURRET, 100);

}

RotateMotor(TURRET, -100, CENTER_TURRET);

Off(TURRET);

while (TRIGGER != 1)

{

OnFwd(FIRE, 20);

}

Off(FIRE);

ResetAllTachoCounts(TURRET);

}

/* ============================================================================

<= Rotate Robot's Turret =>

============================================================================ */

task measureSweep() {

RotateMotor(TURRET, 100, CENTER+SWEEP);

}

/* ============================================================================

<= Measur Ambient Light Level =>

============================================================================ */

void measure_light() {

ambient = 0;

start measureSweep;

while (MotorRunState(TURRET) == OUT_RUNSTATE_RUNNING) {

level = LASER;

if (level > ambient) ambient = level;

}

ambient += AMBIENT_MARGIN;

TextOut(0, LCD_LINE6, "Ambient ");

NumOut(50, LCD_LINE6, ambient);

}

/* ============================================================================

<= Check for Target =>

============================================================================ */

void check() {

level = LASER;

if (level > max) {

target = ANGLE;

max = level;

}

/* ============================================================================

<= Scan Robot's Turret =>

============================================================================ */

void scan() {

max = 0;

if (ANGLE > CENTER) {

// look left

// OnRevReg(TURRET, SCAN_SPEED, OUT_REGMODE_SPEED);

OnRev(TURRET, SCAN_SPEED);

while (ANGLE > CENTER-SWEEP)

check();

}

else {

// look right

// OnFwdReg(TURRET, SCAN_SPEED, OUT_REGMODE_SPEED);

OnFwd(TURRET, SCAN_SPEED);

while (ANGLE < CENTER+SWEEP)

check();

}

Off(TURRET);

}

/* ============================================================================

<= Turn Laser Off =>

============================================================================ */

void SetSensorLightInactive(const int port) {

SetSensorType(port, SENSOR_TYPE_LIGHT_INACTIVE);

SetSensorMode(port, SENSOR_MODE_PERCENT);

ResetSensor(port);

PlayFile("LaserOff.rso"); // Audible "Laser is Off!"

while (SoundFlags() != SOUND_FLAGS_IDLE);

}

/* ============================================================================

<= Turn Laser On =>

============================================================================ */

void SetSensorLightActive(const int port) {

SetSensorType(port, SENSOR_TYPE_LIGHT_ACTIVE);

SetSensorMode(port, SENSOR_MODE_PERCENT);

ResetSensor(port);

PlayFile("LaserOn.rso"); // Audible "Laser is On!"

while (SoundFlags() != SOUND_FLAGS_IDLE);

Wait(250);

PlayFile("LaserOn.rso"); // Audible "Laser is On!"

while (SoundFlags() != SOUND_FLAGS_IDLE);

Wait(250);

}

/* ============================================================================

===============================================================================

<= Main Robot Control =>

===============================================================================

============================================================================ */

task main() {

ClearScreen();

SetSensorLightInactive(LASER_PORT);

PlayFile("LaserOff.rso"); // Audible "Laser is Off!"

while (SoundFlags() != SOUND_FLAGS_IDLE);

start LaserReading;

SetSensorTouch(TURRET_PORT);

SetSensorMode(TURRET_PORT, IN_MODE_BOOLEAN);

SetSensorTouch(TRIGGER_PORT);

SetSensorMode(TRIGGER_PORT, IN_MODE_BOOLEAN);

Wait(250);

PlayFile("Aligning.rso"); // Audible "Aligning!"

while (SoundFlags() != SOUND_FLAGS_IDLE);

align();

measure_light();

SetSensorLightActive(LASER_PORT);

PlayFile("SanningForTarge.rso"); // Audible "SanningForTarget!"

while (SoundFlags() != SOUND_FLAGS_IDLE);

while (true) {

scan();

}

StopAllTasks();

}

Short URL: http://tinyurl.com/hgy7w8a

lego, mindstorms, laser, guided, shooter