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High Brightness Remote Controlled White LED Bulb Group 27 Tzong-Yu Chan Justin Czarnowski  April 30 th , 2009 Introduction High brightness LED light fixture could replace current commercially available white LED light bulbs which are about 300 lumens

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High Brightness Remote Controlled White LED Bulb

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High Brightness Remote Controlled White LED Bulb

Group 27

Tzong-Yu Chan

Justin Czarnowski

 April 30th, 2009


Introduction

  • High brightness LED light fixture could replace current commercially available white LED light bulbs which are about 300 lumens

  • The RF control feature allows user to control multiple light bulbs simultaneously


Features

  • High brightness light output equivalent to 100W incandescent light bulb (1700 lm)

  • RF wireless control

    • on/off

    • brightness dimming

  • Compatible with 120Vac from the outlet

  • Low power consumption, high reliability


High Brightness Remote Controlled White LED Bulb

Power Supply

LED units

Receiver

Remote Control


System Overview

  • Hardware:

    • Power Supply, RF Receiver, Dimming Unit, LED Light String, RF Transmitter

  • Software:

    • A/D and serial transmission code for remote PIC

    • Serial reception and PWM output code for receiver PIC


System Overview

Power Supply Circuit

LED Current Driver

Heat Dissipater

Bridge rectifier

AC Power Source

Power Converter

PIC

LED Circuit

RF Receiver

Wireless Remote

RF Transmitter

RF Transmitter

9V

Battery

5V regulator

Potentiometer

and switch

PIC


Hardware Overview

  • Power Supply

    • Take 120Vac power and convert to stable maximum 33 Vdc and 1 Amp

    • Transfomerless to reduce space and weight

  • Dimmer Unit

    • Change the amount of current going through the LEDs by varying the PWM duty cycle

  • RF Receiver & Transmitter

    • Allow user to control the light bulb remotely


Power Supply

  • Can supply up to 33Vdc to the LED circuit

  • Transformerless

  • Maximum current: 1Amp

  • 120Vac input directly from the wall outlet


Tranformerless Power Supply

  • Resistive Transfomerless Power Supply


Tranformerless Power Supply

  • Capacitive Transfomerless Power Supply


Tranformerless Power Supply

  • MOSFET Gate Controlled Transfomerless Power Supply

Source: Supertex Application Note AN-H52


HV9931

  • Fixed frequency PWM controller IC designed to control LEDs

  • Input voltage: 0~470V

Source: Supertex Application Note AN-H52


Power Supply

Source: Supertex Application Note AN-H52


Power Supply Testing Result


Wireless Remote Control

Objectives:

  • Operate up to 30 feet away from bulb

  • Line-of-sight not required

  • On/off and dimming capability

  • Predictable behavior when out of range


Wireless Remote Control

Design:

  • Use RF transmission: Linx LC TX/RX pair

  • Remote PIC captures analog brightness value as an 8-bit digital value using ADC

  • 8-bit value transmitted wirelessly via Linx chips

  • Receiver PIC outputs PWM signal with duty cycle corresponding to 8-bit value


Wireless Remote

Receiver Side

Wireless Remote

RF Transmitter

RF Transmitter

9V

Battery

5V regulator

RF Receiver

PIC

Potentiometer

and switch

PIC

to LED current driver…


Wireless Remote Schematic

Voltage Regulator

PIC

RF Transmitter


Wireless Remote

Receiver

Remote

Linx RF receiver

Linx RF transmitter

PWM output to LED current driver

Brightness control potentiometer


RF transmission

Baud rate = 9600 bps => 104us period

Data input to transmitter

(remote)

Data output from receiver

  • Data matches -- wireless operation confirmed!

  • Wireless range only about 3 inches…


RF transmission verification

  • 8-bit brightness value is padded with leading and trailing “magic bytes”

  • Receiver only changes PWM duty cycle (brightness) if magic bytes are correct

  • Ensures predictable bulb operation even when remote goes out of range, loses power, etc.


PWM signal

  • Receiver PIC converts the 8-bit data into a PWM duty cycle percentage

  • PWM signal controls LED current driver which in turn controls brightness

  • The resulting brightness of the LED bulb is proportional to the duty cycle of the PWM signal

PIC (receiver)

PWM signal

Serial data (8-bit)


25%

2%

T = 20uS

75%

98%

50%

Duty cycle = 100% (maximum brightness)

PWM signal

Duty cycle = 0% (completely dark)


Challenges

  • Originally intended to use MAX611 chip to convert 120 VAC to +5 VDC for powering Linx chip and PIC on receiver side

  • MAX611 is no longer available

  • Workaround: use 9V battery on receiver for demonstration purposes


  • Potential solution:

    BIAS Power BPI 200-05-00

  • Requires minimal redesign

    of receiver circuit

  • Would require large quantity order

Source:

www.biaspower.com


LEDs

  • Cree XR-E R2 bin

  • Brightest commercially-

    available single LED

  • 228 lumens output at

    1000 mA input current

  • Forward voltage ≈ 3.7 V

  • Star heat sink for heat dissipation


LEDs

  • 100W incandescent bulb output: ≈1700 lumens

  • (228 lumens/LED) x (10 LEDs)

    = 2280 lumens!


XR-E R2 performance

Source: “LED Flux Spreadsheet.” Adam Royall Smith


Actual Performance

  • LED power supply does not output as much current as designed

  • Designed to output 1000mA but only outputs 100mA average!

  • LEDs relatively dim…


Actual Performance

  • Actual maximum output is only 40 lm/LED

  • Total max. output

    is only 400 lm

  • Falls short of

    design goals


Successes and Failures

Failures:

RF range only a few inches

Very low current output

Underperformance of current driver circuit caused low brightness

Brightness control not smooth for output of high brightness LEDs

Successes:

RF communication functional

Transformerless LED driver

Obtained high brightness and high efficiency LEDs

Smooth A/D conversion on remote PIC

Receiving PIC decodes data and outputs appropriate PWM signal


SWOT Analysis

  • Weaknesses

  • Limited wireless range

  • Low brightness due to current driver circuit

  • High cost

  • Buzzing sound at high brightness

  • Strengths

  • Low power consumption

  • Transformerless

  • High brightness / high efficiency LEDs

  • Wireless control

  • Dimming capability

  • Opportunities

  • Potential to replace incandescent bulb

  • Could be used in hard-to-service areas due to longer lifetime

  • Threats

  • Not isolated from AC line

  • Undervoltage condition


Sources

  • http://www.cree.com/products/pdf/XLamp7090XR-E.pdf

  • http://www.biaspower.com/

  • “LED Flux Spreadsheet.” Adam Royall Smith http://filebox.vt.edu/users/adsmith4/Lights/Emitter%20Flux%20Datacalc.xls

  • http://www.linxtechnologies.com/Products/RF-Modules/LC-Series-Low-Cost-Transmitter-and-Receiver-Modules/

  • www.selectronic.fr/includes_selectronic/pdf/Maxim/MAX_611.pdf

  • Supertex Application Note AN-H52 www.supertex.com/pdf/app_notes/AN-H52.pdf

  • Supertex Unity Power Factor LED Lamp Driver Datasheet www.supertex.com/pdf/datasheets/HV9931.pdf

  • “The Nature of Light.” http://www.ccri.edu/physics/keefe/light.htm


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