tri-color, flashing LEDs and 7-colour LEDs
LEDs can also be obtained in a range of novelty effects as well as a red and green LED inside a clear or opaque lens. You can also get red, blue, white, green or any combination inside a LED with 2 leads. Simply connect these LEDs to a 6v supply and 330R series dropper resistor to see the effects they produce.
Some LEDs have 3 leads and the third lead needs to be pulsed to change the pattern. Some LEDs can be reversed to produce a different color. These LEDs contain red and green and by reversing the voltage, one or the other color will illuminate. When the voltage is reversed rapidly, the LED produces orange. Sometimes it is not convenient to reverse the voltage to produce orange. In this case three leaded LEDs are available to produce red, green and orange.
Flashing LEDs contain a chip and inbuilt current-limiting resistor. They operate from 3.5v to 12v. The flash rate will alter slightly on different supply voltage. You can get 3mm and 5mm versions as well as high-bright types and surface-mount.
Novelty LEDs can have 2 or three leads. They contain a microcontroller chip, inbuilt current-limiting resistor and two or three colors. The two leaded LEDs cycle through a range of colors, including flashing and fading. The three leaded LEDs have up to 16 different patterns and the control lead must be taken from 0v to rail volts to activate the next pattern.
LEDs LEDs LEDs
There are hundreds of circuits that use a LED or drive a LED or flash a LED and nearly all the circuits in this eBook are different. Some flash a LED on a 1.5v supply, some use very little current, some flash the LED very brightly and others use a flashing LED to create the flash-rate.
You will learn something from every circuit. Some are interesting and some are amazing. Some consist of components called a "building Block" and they can be added to other circuits to create a larger, more complex, circuit.