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Laser-Guided Turret. ECE 445 – Senior Design Group #6 Ryan Nevell, Smit Shah, Sharlene Wu. Introduction. Capture laser dot and control an Airsoft turret to fire at target Designed for fun - Targeted towards Airsoft audience

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laser guided turret

Laser-Guided Turret

ECE 445 – Senior Design

Group #6

Ryan Nevell, Smit Shah, Sharlene Wu

  • Capture laser dot and control an Airsoft turret to fire at target
  • Designed for fun - Targeted towards Airsoft audience
  • Could be expanded to infrared detection, motion detection, live firearms, etc
  • Uses 2 cameras for 3D world view
  • Works with ordinary laser pointers
  • Serial communication between system and turret
  • Accurate up to 16 ft.
  • Harmless projectiles
  • Built by machine shop
  • American Precision Stepper motors (23H-502U)
  • Soft Air Defender of World Peace
circuit components
Circuit Components
  • Allegro SLA7060M Motor Drivers
  • PIC16F877
  • HIN232CP RS-232 transmitter/receiver
  • NTP75N06 Power MosFET for firing mechanism
  • F1100E 20MHz Oscillator
  • TXM-900-HP-2 RF Wireless Transmitter
  • RXM-900-HP2 RF Wireless Receiver
american precision stepper motors
American Precision Stepper motors
  • Pan Motor driver draws about 0.35 A current at 11 Volts
  • Tilt Motor driver draws about 0.25 A current at 11 Volts
  • Motors has each step of 1.8°
  • Pan Motor has freedom of 360°
  • Tilt motor has freedom of 40°
motor drivers
Motor Drivers
  • SLA7060M Allegro Stepper Motor Drivers
  • Operates both motors in Half Step Mode giving 0.9° of precision
  • A reference Voltage and Sense resistors are used to specify current through motor windings.
firing mechanism
Firing Mechanism
  • Uses a 5V DC Motor to reload and fire.
  • It requires up to 2A current when firing
  • Generates noise
  • Uses a power MOSFET controlled by PIC
  • Switch needed to stabilize firing current
pic16f877 functions
PIC16F877 Functions
  • Receives serial data sent by system
  • Decodes the data and check for errors
  • Send back information to system about operation
  • Controls both motor driver direction and clock inputs to motor Driver
pic16f877 cont
PIC16F877 (cont.)
  • Controls firing mechanism
  • Monitors reset position and performs positions correction
wireless schematic removed
Wireless Schematic (Removed)
  • LINX HP-2 Series receiver and transmitter
  • Encoding and decoding algorithm
  • Operating frequency 921.37MHz
communication protocol
Communication Protocol
  • 3 or more identical bits in a row (000 or 111) drops accuracy over wireless
  • A bit is always followed by its inverted bit
  • Contains 3 data bits and 1 command/data specify bit
  • For example in 10101010



Command Code



Motor to right)

  • Labtec Webcam Pro
  • 640 by 480 pixel resolution, 24 bit color
  • Facing in generally the same direction and level
laser detection algorithm
Laser Detection Algorithm
  • Existing algorithms rely on laser to be red or significantly brighter than rest of scene
  • Looks for increases in brightness
  • Box method used to check appropriate size
    • More efficient and simpler than blob method
matlab configuration
Matlab Configuration
  • Our program takes picture pairs from cameras, one for left camera, one for right camera
  • Matlab program by Jean-Yves Bouguet (Caltech)
  • Pinhole camera model
matlab cont
Matlab (cont.)
  • A coordinate system is initialized with the left camera being at the origin
  • Rotation and transformation matrices relate the right camera to the left
  • Intrinsic parameters (focal length, principal point) are sent to the program as well
stereo triangulation
Stereo Triangulation
  • Uses pinhole method
  • Draws a line from image planes to the point
  • Utilizes least-squares method to determine depth of point (Z)
  • Calculates the disparity
targeting process trajectory
Targeting Process - Trajectory
  • Adjustable Pan Plane and Zero vector
    • Allows cameras to be out-of-level to turret
    • Allows fine-tuning of turret aim
  • More complicated ballistic calculations abandoned when Nerf gun failed
pc software
PC Software
  • Decided to use Linux
    • Thought Video4Linux would be easiest
  • x86 Linux drivers support only 1 camera
  • Use network to combine 2 PC’s
  • Multi-threaded, written in C
    • Sleep time between camera frames, turret commands
pc software cont
PC Software (cont.)
  • Modular design
    • Various input/output plug-ins
    • Easily expandable to 3+ cameras
  • Simple console UI to change parameters at runtime
  • Specially built version of Knoppix used for development
wireless transmitter receiver testing
Wireless Transmitter/Receiver Testing
  • Best performance when operated on separate breadboard from Crystal Oscillator
  • Firing mechanism adds noise to receiver circuitry causing false detection
  • Tried to disable receiver while firing
targeting accuracy
Targeting Accuracy
  • At distances between 7 and 10 feet, targeted point averaged within 0.548” of laser point
  • Depth accuracy much worse than horizontal/vertical – especially at long range
    • Might clear up with larger calibration grid
targeting and firing accuracy
Targeting and Firing Accuracy

26 Shots fired at various positions at distances between 10 and 16 feet.

original design specifications
Original Design Specifications
  • Accurate up to 30 ft from cameras
  • At 30 ft, BB’s will hit target within 1 ft radius
  • Wireless configuration
current design
Current Design
  • Accurate up to 16 ft from cameras
  • At 16 ft, BB’s will hit target within 1 ft radius
  • No Wireless due to noise
  • Laser detection
    • Cameras saturated by laser
    • Laser cannot be seen at 30 ft
  • Camera driver limitation
  • Defective equipment
  • Finding correct stereoscopic algorithm
  • Firing circuit generated too much noise
future hardware development
Future Hardware Development
  • Stronger motors
  • Timing belts
  • Enhance wireless performance
  • Better cameras
  • Infrared cameras
  • Sell cameras pre-mounted and calibrated
future software development
Future Software Development
  • GUI interface
  • Infrared detection
  • Motion detection
  • Implement camera calibration into program
  • Calibrate cameras before production
  • Professor Jonathan Makela
  • TA: Jason Skowronski
  • Professor Seth Hutchinson
  • TA: Jonathan Holm