1. ECE 445: Robotic Microphone Stand
Alejandro Gomez and Dennis Yuan
University of Illinois at Urbana-Champaign
Fall 2012

2. Outline
Introduction
Requirements
Design Overview
Control Scheme

3. Introduction
Objective: Create a prototype robotic microphone stand for Pogo Studios
Benefits:
Precision control of microphone position
Protection of personnel from potentially dangerous recording environment
Enhance recording environment

4. Requirements Wireless control Movement along x,y,z
Store and recall positions
Be less expensive that similar products

5. Power supply and voltage regulation Computer and control interface
Design Overview
Power supply and voltage regulation
Stepper motors
Motor control circuit
Microcontroller
Sensors
Bluetooth TX/RX
Power
Information
Computer and control interface

6. Power Supply AC to DC power supply 5V output, 35W
Directly powers the microcontroller, motor controllers, and voltage regulators

7. 12V Voltage Regulation Motor voltage requires 8-35V
Using TI LM A switching regulator in a boost configuration
Challenges: burned out 3 samples due to not having large enough capacitors

8. 12V Voltage Regulation

9. 12V Voltage Regulation Had to change from original 2.7V regulator
Significant voltage spikes and transients

10. 3.3V Voltage Regulation Bluetooth module requires 3.3V
Using TL497A 300mA switching regulator in step-down configuration

11. 3.3V Voltage Regulation

12. 3.3V Voltage Regulation
Used the 3.3V regulated output from Arduino Uno for the demo

13. Motors
Stepper Motors
200 steps/revolution
1in/rev lead screws

14. Motor Control IC Simplifies control signals to just STEP and DIR
Contains active current limiting into the motor
Problems: burned out our original chips, control signals were shorting

15. Motor Control IC

16. Bluetooth Communication
Using the RN-41 with integrated antenna
Relays data to and from microcontroller
Original design included using just the chip instead of it mounted on breakout board. Igor suggested we just use the breakout board version, since we had tested it already.

17. Bluetooth Communication

18. Bluetooth Communication
“1” = x31 =
“a” = x61 =
“A” = x41 =
“!” = x21 =
Automatic discovery mode
SPP (Serial Port Profile)
ASCII is pushed from least significant bit to most significant bit 1 1 1
Hardset to 9600 baud rate

19. Bump Sensors Used to detect limits of movement range
Output goes straight to microcontroller
NC/Vcc
NO/GND
Common

20. Microcontroller ATMega328 on Arduino Uno 5V to 3.3V circuit for TX/RX
3.3V source from arduino board used to power bluetooth in final demo In
Out 5V
3.296V 0V
.216V
Voltage drop of schottky diode

21. Microcontroller

22. PCB Fabrication Utilized ECE Service Shop Eagle 6.2.0 Lite
Total of 2 revisions
Had to make a second revision for changing 2.7V regulator to 12V regulator

23. PCB Fabrication
Isolation of 60mils, had to make own footprint in Eagle for the bluetooth part

24. PCB Fabrication
3 separate power regulators, 1 for each motor for simplicity, testing modularity, and ability to use lower power parts. Had to make own footprint for the motor controller breakout board.

25. Control

26. Motor Movement
Dependent on user key presses, to move in the x, y, z plane. motorSteps(steps,delay,x,y,z)
Also moves to a certain input location, and a stored location. goToLocation(x,y,z)
Moves to the origin each time the program is started. goToOrigin()

27. motorSteps(steps,delay,x,y,z)
Moves motors a specific number of steps
Delay of microseconds after HIGH and after LOW signals are sent to the motor
x, y, and z can be either 1, -1, or 0 to move each motor clockwise, counterclockwise, or keep it still.

28. Precision The lead screws move 1in per revolution.
We move 50 steps per key press, which gives us 1/5 in precision

29. Storing Position
When key ‘c’ is pressed, listens to a key from ‘0’ to ‘9’ to be pressed, then stores position memory.
To return to a stored position, press a key from ‘0’ to ‘9’.

30. Keyboard Inputs j, l -> +/- x axis i, k -> +/- y axis
q, a -> +/- z axis
c then 0 to 9 -> store location
0 to 9 -> restore location
g then coordinates -> go to location
r -> reset position to origin

31. Feedback x, y, and z location are displayed on the computer screen
Stored locations are also displayed

32. Bumpers Program is always listening if any bumper is pressed
When a bumper is pressed it stops all movement
Resets location in software in case there were any previous errors in movement

33. Simulation
Used JavaScript to create a simulation of the movement of the robot
Programed it keeping in mind Arduino functions and programing structure (setup(), loop(), digitalWrite(), etc.)

34. Met Requirements? Wireless control – yes, using bluetooth
Movement along x,y,z – yes
Store and recall positions – yes, in memory
Be less expensive than similar products – yes, production budget < $300

35. Improvements Add pan/tilt functionality Fix 3.3V regulation
Incorporate microcontroller on PCB
Grease lead-screws
Make enclosure for PCBs
Incorporate JavaScript plugin for GUI
More robust music algorithm, to play arbitrary songs easily

36. Special Thanks Igor Fedorov Mark Smart and the ECE Service Shop
Scott McDonald and the ECE Machine Shop

37. Stepper Motor Music!
Robot noise when moving is dependent on speed of the motors
We can map the frequency of a musical note to delay between steps.
delay=500000/f
motorSteps(steps, 2040, 0, 0, 1); // B 246 Hz
motorSteps(steps, 2273, 0, 0, 1); // A 220 Hz
motorSteps(steps, 2551, 0, 0, 1); // G 196 Hz …

38. Stepper Motor Music!