Project Design Proposal

ENGR 103 - Spring 2013

Freshman Engineering Design Lab

“Daylight Matching LED Luminare”

Project Design Proposal

Date Submitted: April 9th, 2013

Submitted to:	Ben Cohen, bc3262@drexel.edu
Group Members:	Mark Cardish, mfc63@drexel.edu
	Kevin Lubinski,  kml364@drexel.edu
	Devin McGinty, dlm348@drexel.edu

Abstract:

The objective of this project is to build a daylight-matching LED luminaire. The utility of such a device is to illuminate a room with colored LEDs to simulate the color temperature at different times of a day.

Our group of three members is working collaboratively with another group towards a complete daylight-matching LED luminaire. Our group's objective is to plan, design, and build the electronics for the luminaire. Our partner group is working on fabricating the structure to house the lighting electronics.

1           Introduction

Daylight has been shown to have significant positive effects on people. Regular exposure to ordinary daylight promotes productivity and health. Eyes are naturally adjusted to function better in sunlight, and prolonged exposure to incandescent or fluorescent light can cause fatigue and eyestrain. Sunlight has also been seen to improve emotional and psychological functions. Lack of exposure to sunlight can induce depression, lethargy, and Seasonal Affect Disorder.

Ideal natural light's color temperature changes significantly during the course of a day due to the refraction of daylight through the atmosphere. Early day is dominated by temperatures of 6,500K to 30,000K, which are blue and white hues. Later times in the day have temperatures between 4,000K and 5,000K, and as low as 2,000K during sunset. These hues are more orange, amber, and red.

Common incandescent and fluorescent lights have static color temperatures typically within the range of 2,500K to 3,500K. Some manufacturers currently sell bulbs with higher, more white color temperatures; however those are still static. The purpose of a daylight-matching LED luminaire is to illuminate a room with white light mixed with the appropriate color temperature for the time of day. The spectrum of the luminaire is dynamic, providing higher temperatures to promote productivity and stimulation during morning and mid-day, and lower temperatures in the evening to avoid eye strain.

2           Deliverables

Describe in detail what you will produce at the conclusion of the project: examples include physical prototypes, computer models, simulation results, algorithms and programs, design studies, lab test results.

This project will end with the creation of a control system for RGB LED’s that can be adaptively scaled and modified due to it’s modular nature. This prototype control system will then be ready for refinement and shrinking it down into a smaller form factor. The control system will be in hardware and software, using an Arduino Duemilanove to control the LED packages. The LEDs will be in an analog strip format, which allows for easy packaging and prototyping, as well as a modular nature for repair and durability. The software control system will be embedded inside of the Duemilanove for the prototype. It will be written using wiring/processing; the standard Java based language for Arduino. The algorithm will basically start by controlling the LEDs to follow an automated sunrise to sunset light spectrum, mimicking the sun’s spectrum by using PWM(Pulse Width Modulation) to control the mass analog input of the LEDs to follow the correct spectrum over a 12 hour cycle. The spectrum correctness will be determined using dialux and various research forays.

3           Technical Activities

These next sections will cover a higher level, relatively non specific overview of the tasks associated with this design project. It will cover the approach to the Power delivery for LEDs and the coupled Hardware/Software control of the LEDs.

3.1        Electrical System

Delivering stable, clean power is a concern when dealing with this many LEDs. We have decided that it is best to approach with an AC/DC transformer to convert the normal 120/240v AC into roughly 12V 20A DC current to drive the LEDs cleanly, and to maximize operational efficiency and life. This will most likely be done with a simple transformer circuit that takes in the default AC current used in buildings and converts it to the DC current used by semiconductor electronic devices.

3.2        Hardware/Software Control

The control system cannot be run from an Arduino directly, we have to use shift registers to expand the PWM output of the Arduino in-order to control the amount of LEDs that we are interested in using. The logic control is then coupled with the power supply to drive the LEDs and protect the Arduino from over-current damage. Shift Registers allow us to extend the control of the Arduino from the clock, latch and data pins. We will be using the open-source ShiftPWM library for Arduino to control the shift registers. The hardware and software work closely in this project since there isn’t much of higher level interaction going on, since we are interfacing with only the shift registers at a software level. The control is done in hardware based on the Arduino’s clock, latch and data pins that drive the shift registers to move data to control the LED power levels and on/off state.

3.3        LED Interface

The interface for the LEDs will be in a strip format, which are simply flexible, applicable LED strips that combine RGB LEDs to separate cathodes with a common anode, or vice versa. These are analog, which means you can only control the complete strip and the total brightness/color, but not the individual LED color profile. This is good for our purposes, as it allows us to create an even color profile across the string of LEDs which is due to the hardware logic using shift registers to control the responsible LED strips. For the white backlight, we will also be using strips, but they will be single color white, which means that we only control the brightness over time.

4           Project Timeline

Week	1	2	3	4	5	6	7	8	9	10
Planning	X	X
Research	X	X	X	X
Coding/Programming			X	X	X	X
Electrical Design					X	X	X	X
Testing							X	X	X	X
Final Report Preperation						X	X	X	X	X

Table 1: Project Timeline (Subject to change in actuality

5           Facilities and Resources

To complete this project, several outside resources will be needed. that the group does not already possess. Group 6 will provide the mechanical design for the light that will have approximately 13 meters of LED light strips attached. These LED strips will need to be purchased from an outside source, along with LED strip drivers and an AC/DC transformer. An arduino will also be used in the project, but that does not need to be purchased because they the group already owns one. Also, shift registers, mosfets, and other associated electronic components will be purchased to add outputs to the arduino. The LED light assembly in the Hess lab will also be used for research purposes and for initial design.

6           Expertise

The project does require some knowledge and willingness to learn certain basic ideas of circuitry and circuit theory, digital to analog control systems, and prototyping/soldering. Arduino is a very easy platform to get interested in, and is very user friendly, based upon the wiring/processing programming language and hardware design, it is an excellent starting point for the prototype to create a production ready, cost effective model. All of the group members have demonstrated either a previous grasp of the knowledge prior to this project, or they are willing to learn from those who do.

7           Budget

Category	Projected Cost
LED Strips	~$200
Electronic Components	~$80
TOTAL	~$280

Table 2: Rough Budget for project, subject to change based on price variance between suppliers and changes to design.

7.1        LED Strips

These are strips that contain RGB LEDs and White LEDs for the basic construction of the lighting and backlighting needed to create this fixture.

7.2        Electronic Components

This includes the various components needed to build the LED driver circuits, which includes the MOSFETs, Shift Registers, Resistors, Wire, Perf Board, Solder, and extras to account for issues and defective products/errors.