Interactive LED Staircase Modules Group 38 Mike Udelhofen ECE 445 April 26, 2012

Motivation: Health and fitness Energy consumption Visual appeal Objectives

Features 48 RGB LEDs per module 12-bit intensity control per RGB channel Full color spectrum, fading Mode switch – up to 4 modes Calibration switch Modular – no maximum

Physical Design – 6x2 Array 16” 28” 4”

Physical Design 6 x 2 = 12 pixels per module 4 RGB LEDs + 1 photodiode per pixel 6 LED drivers per module 1 microcontroller per module Clear acrylic top cover

Hardware Flow Analog Photodiode Array Digital- Serial Micro- processor Analog LED Driver LED Array 6 PIC16F887TLC5947 RGB, Common Anode A to D conversion I/O + pattern processing A to D conversion I/O + pattern processing

Photodetectors Advanced Photonix PDB-C156 6 x 2 array 120° viewing angle Output between:.18V (dark).31V (light)

Microcontroller - Input ADC – V ref -, V ref + Two voltage division circuits Sets bounds on input voltages.15 to bit digital resolution 12 photodetectors

Software Flow

Software – Algorithm Processing Mode 0: basic illumination mode Mode 1: unused Mode 2: modular ripple mode Mode 3: test algorithm mode

LED Drivers TI TLC mA max, run at 25mA 30MHz capability 24 channels – each drives 6 pixels (one color) 12 bit resolution

LED Drivers

LEDs RGB Common Anode View Angle: 25 degrees Forward Voltage: R= V B= V G= V Current: 20-25mA Size: 5mm Luminosity: 6,000- 9,000 mcd

Design Changes Original PIC16F877A No internal clock 7 ADC channels 2 PICs / module “Main” level Limits modularity Final PIC16F887 Internal clock 14 ADC channels 1 PIC / module No “main” level Modularity is controlled from each module

Testing and Verification 1.All powered units receive adequate power 1.Microprocessors receive 5V 2.LED drivers receive 5V 3.RGB LEDs receive no more than 3.2V 1. 1.A voltage between 4.5 and 5.5V is measured at VDD pins. 1.Measured 4.8V 2.A voltage between 4.5 and 5.5V is measured at VDD pins. 1.Measured 4.7V 3.A voltage between 2 and 3.2V is to be measured from each pin to ground 1.Measured 2.0V, 3.2V, 3.2V at constant illumination

Testing and Verification 2. PIC reference voltages are within photodiode range 1.Lower reference voltage is within spec 2.An upper reference voltage is within spec 3.Minimum photodiode voltage is >.15V 4.Maximum photodiode voltage is <.48V 2. 1.V ref - <.15V must be measured with multimeter at pin A2 1.Measured.106V 2.V ref + >.480V must be measured at pin A3 1.Measured.489V 3.V min =V dark >.15V 1.Measured.18V when completely covered 4.V max =V light <.48V 1.Measured.31V when under illumination by flashlight

Testing and Verification 3. Output to LED drivers is properly timed 3. Measure 288 clock pulses per one XLAT pulse on oscilloscope See next slide

Testing and Verification

4. Each pixel can be addressed individually 1.Count up through addresses from PIC, enabling each with maximum current for 500 ms. Implemented as test mode in code Each pixel is illuminated individually for 500 ms 1.Test algorithm successful

Successes and Challenges Successes: Photodetection, ADC LED illumination PCB fabrication I/O routing and algorithms

Successes and Challenges Main Challenges: Performance limited by microcontroller Too much LED data processing – slow Man-hours - soldering

Closing Thanks to Prof. Carney, Mustafa, Alex, and the rest of the course staff! Questions?