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Electrical and Computer Engineering iLights Nick Wittemen, EE Chris Merola, EE José Figueroa, EE Matt Ryder, EE Midway Design Review.

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Presentation on theme: "Electrical and Computer Engineering iLights Nick Wittemen, EE Chris Merola, EE José Figueroa, EE Matt Ryder, EE Midway Design Review."— Presentation transcript:

1 Electrical and Computer Engineering iLights Nick Wittemen, EE Chris Merola, EE José Figueroa, EE Matt Ryder, EE Midway Design Review

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

3 3 Electrical and Computer Engineering Block Diagram

4 4 Electrical and Computer Engineering Specifications Sample frequency data often enough to produce this effect Package, transmit, and process data fast enough to keep up with music Able to switch light levels fast enough to produce desired visual effect

5 5 Electrical and Computer Engineering Timing Specifications  Need to switch light level fast enough to keep up with music  720 bpm = 12 Hz Sample audio at 24 Hz to reproduce using Nyquist Theorem.  Triac phase control allows level to be switch every half cycle of AC, 120Hz  We are able to extract data at this rate from iTunes

6 6 Electrical and Computer Engineering Transmit Timing  iTunes SDK is designed to make FFT of audio playing available fast enough for visualization  Delay to process data and send to serial is negligible (<1ms).  Baud rate chosen, 19.2 kHz. Only transmitting 32 bits = 1.7 ms  Microcontroller will check for and process new serial data once during every 120 Hz power cycle. Worst case delay 8.3 ms  Total delay approx 11 ms in worst case. Will not be an issue.

7 7 Electrical and Computer Engineering USART  On our ATMEGA168 the USART is constantly handled in the background  We will allocate time at the end of each half wave cycle to update light level data  This will limit our brightness range at the very low end, 5% brightness control reduction gives us 6400 clock cycles at 16 MHz  ATMEGA168 processes most instructions in 1-2 cycles. Multiply and LW each take 2 cycles.

8 8 Electrical and Computer Engineering iTunes Interface  Software uses iTunes visualizer SDK to retrieve frequency data  iTunes loads our *.dll file  Able to access a 256 point FFT  Each point returns magnitude contained as a Uint8, unsigned 8 bits, 256 steps of resolution

9 9 Electrical and Computer Engineering Sample GUI : Current Progress Screen-shot of current version of the GUI:

10 10 Electrical and Computer Engineering Hardware: Triac BTA20-700CW Snubberless  Triacs allow switching of an AC signal Triggered by the Arduino and zero-cross detection  Able to handle peak power of 14kW which is more than twice our design specifications (500W per channel) done intentionally for safety  Phase Control possible (dimming) Integral/area under curve proportional to current through load  Sensitive Gate Triggering (35mA)

11 11 Electrical and Computer Engineering Hardware: Triac BTA20-700CW Snubberless  When doing research many examples found for Triac triggering contained snubber circuits (basic RC or RLC circuits) which smoothed out transients possible from mains but also from controlling inductive loads  Our design: No need for additional circuitry since triac chosen offers suppression making it ideal for phase control Our load is a purely resistive loads (incandescent light bulbs) so there is a much less chance of accidentally triggering the triac

12 12 Electrical and Computer Engineering Pspice Simulation These images show a basic triac circuit with different triggering

13 13 Electrical and Computer Engineering 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

14 14 Electrical and Computer Engineering Serial Communication  The C++ code is given the extracted frequency data to send via serial  This data includes power across each band, which is interpreted via phase control as the brightness  A zero-cross detection circuit determines the period of the sinusoid and the Arduino uses this to trigger the triac at the appropriate delay  Four triac circuits will be independently and simultaneously controlled in this manner

15 15 Electrical and Computer Engineering Communication Link  C++ uses a handle to the serial port to set up the link and write to the port  The Arduino uses Serial.available() to check if there is data on the buffer  The baud rates are matched to 19200 bps for both the C++ and the Arduino codes The Tx and Rx LED’s let us see which way data is being sent We do NOT use overlapped serial communication

16 16 Electrical and Computer Engineering Proposed MDR Deliverables  Prototype of one working Triac controller Able to dim/switch AC power  Able to extract frequency data from iTunes Able to determine feasibility of using iTunes  Able to communicate with microcontroller via USB

17 17 Electrical and Computer Engineering MDR Deliverables: Were they met?  Interface: Yes  Communication: 99% C++ code successfully writes to serial port Currently debugging some underlying issues with an internal reset or interrupt problem with Arduino Unexpected software/hardware incompatibility  Triac Circuitry: 50% Zero-cross detection works successfully Triggering the triac does not, solutions: Triac-triggered opto-isolators Clamping diodes

18 18 Electrical and Computer Engineering Summary Demonstration Comments / Questions?


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