Electrical and Computer Engineering iLights Nick Wittemen, EE Chris Merola, EE José Figueroa, EE Matt Ryder, EE Final Project Review

2 Electrical and Computer Engineering Our Design  iTunes Plug In  PC User Interface  Phase Controlled Lighting  Controls multiple incandescent lights  Provides interactive listening environment

3 Electrical and Computer Engineering Block Diagram

4 Electrical and Computer Engineering 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, updates up to 80 fps)

5 Electrical and Computer Engineering 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 Allows us to write to the serial port as if writing to a terminal window We package the data and transmit as an ANSI string

6 Electrical and Computer Engineering 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  When sent render message we process the data based on user input and transmit update values for all four channels  On screen spectrogram display to assist user in choice of frequency bands

7 Electrical and Computer Engineering User Interface  On screen, built into visualizer options  Uses Microsoft Foundation Classes for event handling Familiar user interface  Each channel has 2 sliders Low and High frequency cutoff  Stores settings when iTunes is closed Settings are backed up in a text file

8 Electrical and Computer Engineering Triac Phase Control  Triacs require external triggering on each half wave of AC power  After being triggered a triac will allow power to flow until the AC waveform crosses zero  We must retrigger at each of these crossing to keep the lights on  Dimming performed by microcontroller detecting zero cross and triggering triac with delay T

9 Electrical and Computer Engineering 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 Electrical and Computer Engineering 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 Electrical and Computer Engineering 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 Electrical and Computer Engineering Critically Timed Loop

13 Electrical and Computer Engineering PCB Design  Standard trace width of 10mils worked for most traces High-current lines required trace width of 80mils and a thickness of 5mils  Traces were made wider and thicker than required to accommodate more heat and current  Turns of more than 45 degrees were avoided EMI reduction

14 Electrical and Computer Engineering Heat Issues  Initial testing of triacs switching ~450W proved heat was going to be an issue for iLights  Heat sink was used, but it was not big enough  Putting iLights in an enclosure would increase heat issues

15 Electrical and Computer Engineering Thermal Management  Heat dissipation of triac is a function of current  Datasheet shows that at maximum operating current (~5A) the heat dissipation will be about 5.1W

16 Electrical and Computer Engineering Thermal Management  Heat sink must be sized based on heat dissipation requirements and ambient temperature difference according to equation:  R_th_ha < 3.96 °C/W

17 Electrical and Computer Engineering Thermal Management  Since heat sinks are in an enclosure, hot air must be removed. Volume of airflow required follows:  Solving for our values gives V> CFM

18 Electrical and Computer Engineering Thermal Management  Heat sink selected has thermal resistance of 2.6°C/W Will keep triacs within 21°C of enclosure air temperature  Fan selected has flow rate of 29 CFM and noise rating of only 22dB Will keep heat sinks within 2°C of external air temperature  Triacs will continue to function until external air temperature exceeds 102°C (~216°F) Triacs will not have heat issues

19 Electrical and Computer Engineering Safety Features  Live (Hot) wire is fused at 20A with a fast acting ceramic in-line fuse Each output channel is also individually fused at 5A with a quick blow in-line fuse to assure that the max power per channel is not exceeded  Push wire receptacles were chosen over conventional screw terminals reduced exposed contacts within the enclosure, each receptacle rated for 15A

20 Electrical and Computer Engineering Summary Demonstration Comments / Questions?