While using a digital multimeter to diagnose electrical problems on customers’ equipment, I frequently hear the comment, “I’ve got one of those multimeter things, but I never learned how to use it.” ...

So a few months ago, I stumbled upon a thing at Adafruit.com called a "Charger Doctor" which was really just a Multimeter designed to slip inline with your USB cable. It was $7.50 and I liked it.

Visible light emitting diodes (LEDs) combine high efficiency and long lifetimes. Today, they’re used in a wide range of applications. Extensive R&D efforts by manufacturers have led to the creation of ...