Difference between revisions of "Optoelectronics"
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# [http://en.wikipedia.org/wiki/Light_Emitting_Diode Light-emitting diode From Wikipedia, the free encyclopedia] | # [http://en.wikipedia.org/wiki/Light_Emitting_Diode Light-emitting diode From Wikipedia, the free encyclopedia] | ||
# [http://www.iguanalabs.com/1stled.htm Learning About Transistors and LEDs] | # [http://www.iguanalabs.com/1stled.htm Learning About Transistors and LEDs] | ||
| + | # [http://www.piclist.com/techref/io/led/pulse.htm?key=base+resistor&from= Brighter Appearance through pulsing] | ||
== LCDs == | == LCDs == | ||
Revision as of 08:10, 30 January 2008
Optoelectronics are devices that are some combination of electrical and optical. Perhaps the simplest is the Light Emitting Diode or LED which converts electrical energy into light. A listing of some optoelectronic devices follows.
Contents
LEDs
LEDs are diodes designed to produce visible light.
Commonly a small low power device that makes a not too bright light. High power, high brightness versions are now becoming widely available. The low power ones typically run on a volt or so, at about 10 ma. Typically they are run on higher voltages with a current limiting resistor that sets the current. Current control is almost always required ( often with a resistor ) as LED are very sensitive to small voltage changes. Like other diodes they conduct only in one direction.
When using a LED in a cicuit it's important to use a current limiter such as a resistor. When using resistors measure the foreward voltage drop of the LED with a multimeter, subtract this from the supply voltage, then plug the difference into ohms law to calculate the required resistor value. Different color LEDs all have different voltage drops.
Uses
- Indicator
- Part of 7 segment display
- Light source
External Links
- Light-emitting diode From Wikipedia, the free encyclopedia
- Learning About Transistors and LEDs
- Brighter Appearance through pulsing
LCDs
Liquid Crystal Displays
- Serial - These displays have a microcontroller on the display with a serial or I2C connection. Several builtin fonts are typically included. These displays are very easy to use, but the update rate for a display is very slow. Fullblown bitmap support is usually not available. Typical price for these displays is $50+.
- Parallel - Parallel displays connect to a microcontroller via a parallel interface( the bitwidth varies from 8bits to 32bits ). Displays can have a much faster update rate then serial since they allow arbitrary graphs to be display. The displays are typically much cheaper then serial display starting as low as $20.
Finding LCD displays is not easy since huge distributors such as Digikey have a limited selection.
Some places that do have LCDs for hobby use:
- Sparkfun - Has a good selection of both parallel and serial displays.
- MatrixOrbitral - Specializes in serial display especially the type for direct connection to a PC.
- Jameco - A small selection. Mostly serial.
