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A Charlieplexed digital clock which controls 90 LEDs with 10 pins of a PIC 16C54 microcontroller.. Charlieplexing (also known as tristate multiplexing, reduced pin-count LED multiplexing, complementary LED drive and crossplexing) is a technique for accessing a large number of LEDs, switches, micro-capacitors or other I/O entities, using relatively few tri-state logic wires from a microcontroller.
A PN2222A transistor and 1000 ohm resistor are used A joule thief with two axial inductors replacing the ferrite toroid, shown on a solderless breadboard A joule thief is a minimalist self-oscillating voltage booster that is small, low-cost, and easy to build, typically used for driving small loads, such as driving an LED using a 1.5 volt battery.
Consequently, ranges from around 1.7 to 2.0 volts for red LEDs to around 2.8 to 4.0 volts for violet LEDs. V s w i t c h {\displaystyle V_{switch}} is the voltage drop across the switch in volts: (A) for no switch, use 0 volts, (B) for mechanical switch, use 0 volts, (C) for BJT transistor , use V C E ( s a t ) {\displaystyle V_{CE(sat ...
Relaxation oscillators are generally used to produce low frequency signals for such applications as blinking lights and electronic beepers. During the vacuum tube era they were used as oscillators in electronic organs and horizontal deflection circuits and time bases for CRT oscilloscopes; one of the most common was the Miller integrator circuit invented by Alan Blumlein, which used vacuum ...
LED development began with infrared and red devices made with gallium arsenide. Advances in materials science have enabled making devices with ever-shorter wavelengths, emitting light in a variety of colors. LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface.
Some two-color LEDs are constructed this way, with the 2 dies connected anti-parallel in one chip package. With AC, the LEDs in each pair take turns emitting light, on alternate half-cycles of supply power, greatly reducing the strobing effect to below the normal flicker fusion threshold of the human eye , and making the lights brighter.
An optical transistor, also known as an optical switch or a light valve, is a device that switches or amplifies optical signals.Light occurring on an optical transistor's input changes the intensity of light emitted from the transistor's output while output power is supplied by an additional optical source.
When at least one of the inputs is low, transistor V 1 is turned on, V 2 is turned off, V 3 is turned on and V 4 off, pulling output voltage high. When both inputs are high, V 2 is on, V 3 is off and V 4 is turned on, pulling output low. A digital use of a push–pull configuration is the output of TTL and related families.