RGBulb

Richard Whitney

Background

• Proliferation of LED-based lightbulbs

• Monochrome

• Overpriced

• …But they do last for ~100,000 hours, are extremely efficient, and aren’t a fire hazard

• $0.80 for a year of 12-hour days

Design Requirements

• Must look like light bulb

• Screw into socket, no external components (transformers, etc)

• Easy to use

• Can be constructed in two days (of continuous backbreaking work)

• Be safe

Implementation (Electrical)

• Red, green, and blue light-emitting diodes

• Atmel AVR (Tiny26)

• 3 n-MOSFETs

• 3 potentiometers (50K ohm)

• Various resistors

Implementation (Software)

• AVR reads voltages off of potentiometers via ADC, produces 0-255 integer

• Continuous “for” loop, 255 times between breaks

• R, G, B channels turned off after relative time

• Results in pulse-width modulation

Implementation (Hardware)

• Small transformer from RadioShack

• Disassembled fluorescent socket light

• Vacuform over incandescent bulb

Results

• Worked great on protoboard

• Construction went well

• Migration to breadboard had difficulties

• Current status: some kind of glitch (short) holding G and B potentiometer pins high (possibly)

Future Development

• Fix circuit

• Potential for using AVR to expand capabilities

• -Remote control

• -Timer

• -Contextual response

What I Did With My Weekend

• dx/dt