CHAPTER 10
LEDs
In this chapter, you’re going to learn about LEDs. You’ll see how to select them, test them, and why no
self-respecting robot would reject them.
Light Emitting Diodes (LEDs) are modern miracles. They’re long lasting, impact resistant, inexpensive,
cool to the touch, lightweight, and come in a wide variety of colors and sizes. LEDs are perfectly suited for
battery-powered devices due to their low-voltage and low-current requirements.
When pronouncing “LED,” speak the letters individually, like “el,” “eee,” “dee.” Don’t say it like a word,
such as “led.”
Learning About LED Attributes
Because of their usefulness, LEDs are available in different sizes, shapes, colors, and viewing angles. They
also have various levels of brightness and efficiency.
LED Sizes
The most familiar LED size is T 1 ¾. This terminology comes from the days of miniature incandescent bulbs.
The “T” refers to the bullet shape. The 1 ¾ refers to the approximate diameter in 1/8ths of an inch. What an
odd standard!
The standard T 1 ¾ size is the least expensive and is available in the widest variety of colors (see
Figure 10-1). However, the smaller T 1 size is more modern looking and uses up less space. Surface-mount
LEDs are smaller still, but are more difficult for a hobbyist to experiment with.
LEDs are increasingly being advertised by their metric horizontal diameter. For example, a T 1 ¾ LED is
often listed as 5 mm (millimeters). Although the T 1 ¾ descriptor implies the shape, the millimeter diameter
is more accurate since LEDs are actually manufactured in millimeters, not eighths of an inch.
Using Calipers to Measure LED Diameter
It won’t take long for you to get a feel for LED sizes, since there are only a few common sizes. However, you
can always check by using a caliper.