Final Project for ECE 4180, Georgia Institute of Technology, taught by Dr. James Hamblen

Team Members

• Autumn Caraway
• Michael Marzano

Projcect Description

The goal of this project was to design and implement a remote controlled sliding camera rail using 2 Mbed microcontrollers that communicated with each other over a wireless serial connection. There were 2 parts to this project, the controller (Autumn Caraway) and the camera rail itself (Michael Marzano).

Parts List

Controller

• Mbed NXP LPC1768 Microcontroller
• XBee+Breakout Board
• Potentiometer Joystick+Breakout Board
• 2 Pushbuttons

Camera Rail

• Mbed NXP LPC1768 Microcontroller
• XBee+Breakout Board
• Movo Sliding Camera Rail
• STEPPERONLINE Nema17 Bipolar Linear Stepper Motor
• Mounting Bracket
• 8mm Lead Screw, Length 600mm
• Flexible Coupling
• 8mm Vertical Bearing
• 8mm Anti-Backlash Brass Nut
• Aluminum Sheet
• Assorted Nuts, Bolts, and washers
• Dual H-Bridge Motor Driver
• 12V Power Supply + Barrel Jack

Schematics

Controller


Camera Rail

Pin Outs

Controller

Camera Rail

Note: The VM pin on the H-Bridge is a variable power input that is used to drive the output pins. It is rated for 5-15 volts. To get acceptable performance out of the motor, we had to use a 12V power supply to drive the H-Bridge.

Source Code

Controller
The controller uses interrupts and timers to sample inputs from the joystick and pushbuttons, then creates an ASCII command string that is sent out over a serial connection to the camera rail.

Camera Rail
The Camera Rail uses the Mbed RTOS to efficiently divide up responsibilities into three threads. The main thread uses the LinStepMtr library to control the motor, the second thread reads the serial port and converts the ACII command string into control states and control flags, and the third thread controls the LED status lights.

LinStepMtr Library

The LinStepMtr Library is a custom library, written my Michael Marzano, that controls a STEPPERONLINE Nema 17 Bipolar Linear Stepper Motor via an H-Bridge. It provides a convenient API that allows the user to set the motor's speed in RPM, control the motor's direction, and set the motor to rotate for a given number of rotations. This library also includes the ability to set software stops to limit the clockwise (positive) or counterclockwise (negative) movement of the motor.

Video Demo