iLights

1. Nick Wittemen, EE Chris Merola, EE José Figueroa, EE Matt Ryder, EE iLights Comprehensive Design Review

2. Our Design • iTunes Plug In • PC User Interface • Phase Controlled Lighting • Controls multiple incandescent lights • Provides interactive listening environment

3. Block Diagram

4. iTunes Plug-in • Dynamic Link Library (.DLL) file loaded by iTunes • Runs as a visualizer plug-in, able to access frequency data • Exports frequency data via COM port at rate of visualizer update (set to max, up to 60 fps)

5. Project Sources • Visual Studio Project • Based on VizKit, open source framework built to iTunes Visualizer SDK guidelines • Provides well documented method for implementing an OpenGL visualizer • Serial Communication • Uses Cserial, free source to implement serial port on Windows • Have also used POSIX library (termios.h) for possible expansion to OSX but this library will not compile under Visual Studio for Windows

6. FFT Data • iTunes makes FFT data available to visualizer plug-ins while they are displayed • Sent VisualPluginRenderMessage by iTunes at frame rate specified • This message passes a pointer to FFT • 512 linearly spaced frequency steps, 1 byte each, amplitude only • This is enough information for what we want to do • When sent render message we process the data and transmit as ANSI string (char[9]) • [(11)(22)(33)(44)(\0)]

7. Zero Cross Detection • Our zero cross detector takes advantage of Atmega168 internal clamping diodes • Keeps voltage on input pins between Vcc+0.5V and Vg-0.5V • Using this we are able to connect N terminal to our ground and L to an input pin, produces 5V square wave • Circuit uses series 1Meg resistors on each pin. This will limit current to diode spec of 1mA max up to 1000V

8. Hardware: Triac BTA20-700CW Snubberless • Triacs allow switching of an AC signal • Triggered by the Arduino and zero-cross detection • Phase Control possible (dimming) • Integral/area under curve proportional to current through load • Sensitive Gate Triggering (35mA) • Using an opto-isolated triac driver allows for safe and effective handling of power signals

9. System Uses 2 Microcontrollers • Microcontroller responsible for light dimming must handle 120 interrupts per second and then trigger lights with precise timing • Handling so many interrupts caused problems with serial communication • Solution was to divide up tasks: • First Arduino waits for serial data from computer, sets pin to signal second Arduino that data is available • Second Arduino checks “data available” pin when it has time, after handling light dimming and before next interrupt

10. Arduino 1 • Waits for incoming data on serial port • Parses incoming string stores as 4, 6-bit values (only 6 pins per port available on arduino) • Communicates with second arduino using (2) 6-bit parallel ports and 2 control pins • Control Pin 1 -> Data Available, tells arduino 2 that data is ready • Control Pin 2 -> Send next byte, received from arduino 2 to signal next available message

11. Arduino 2 • Receives input from first Arduino on parallel ports, convert to 6-bit input to timing value from look-up table • Performs zero cross detection for triac timing • Internal clamping diodes combined with external resistors reduce 120VAC to 5VDC square wave • Trigger interrupts on rising and falling edges • Send trigger signals at proper times for light dimming

12. Critically Timed Loop

13. EagleCAD Schematics

16. Design Considerations • EagleCAD schematic almost complete • Need to model DC power supply and off-board connectors • 120VAC lines will be on inner layer of board to minimize trace spacing • Dielectric constant of PCB material is much higher than that of air • Also reduces risk of shock • 120VAC trace width must be about 3mm to reduce resistance and heat buildup.

17. Summary Demonstration Comments / Questions?