Advances in white light-emitting diode (LED) technology have led to large efficiency improvements in lighting for residential and commercial buildings. However, the cost per LED is still much higher than alternatives (old-fashioned incandescents and newer compact fluorescent bulbs). Also, the actual useful lifetime of LED bulbs has proven to be much shorter than the usually predicted 50,000 hours. The problem lies in the structure of a typical LED bulb, which consists of an AC-to-DC converting power supply and several LEDs in a compact package. The converter is a switched-mode power supply (SMPS), and contains a number of failure-prone components - particularly electrolytic capacitors that have notoriously short lifetimes when used in hot environments. Although LEDs are efficient, they still throw off considerable waste heat, which shortens the lifetime of the power supply. To manage the heat, typical LED bulbs require significant heat sinking. Typically, an LED buib fails because the power supply fails - the actual LEDs are probably still perfectly good.Jamming these inherently incapable components together into a single package leads to significant design trade-offs and ultimately higher costs and shorter product lifetimes.
The lifespan of LED bulbs can be increased through the simple act of moving the power supply away from the LEDs. By moving the power supply section “upstream” and locating it in the switch box that is part of every single light circuit, we can design the separate parts of the light system in a more optimal fashion. The light-emitting diodes can be designed with primary consideration on light output rather than thermal properties and the SMPS can be designed for optimal efficieny without the concern of being baked by the waste heat of the LEDs. The lifetime of the SMPS should go up significantly. in addition, this arrangement allows for the possibility of using a single SMPS to power multiple bulbs, rather than then the one-bulb-one-SMPS approach used now, leading to lower overall costs. Also, it becomes easier to integrate a micro controller with the power supply and LEDs, creating a “smart” lighting system.
The purpose of our project is to design, build, and test a system to demonstrate the feasibility of this “distributed-power” approach to LED lighting. The prototype system that we have made includes: (1) LED bulbs that mount into conventional light sockets, (2) an AC-to-DC power regulator that fits into a box for a conventional wall switch, (3) a microcontroller that handles switching and dimming functions for the bulbs and interfaces wirelessly with mobile devices, and (4) a pair of smart-phone apps that can be used to control the opearation of the lights. This project covers the whole spectrum of computer engineering/electrical engineering topics and skills.
From left to right:
Flavia Cavalcanti - CprE - iOS app development
David Wiest - EE - Power Supply Design
Alex Rinehart - CprE - Android App Development
Mitchell Wheaton-EE-Microcontroller Hardware and Firmware Design
Ryan Marion - EE - Microcontroller Hardware and Firmware Design
John Stabenow - EE - LED Bulb Design
Group May 1637
Efficient LED Lighting
Fall 2015 - Spring 2016