[mircemk] built a slick-looking LED tester with a couple handy functions built in. Not only can one select a target current to put through an LED, but by providing a target voltage, the system will ...

This article is a part of CNN Underscored’s Guide to Age-Defying Beauty, a weeklong focus on the essential products, tips and tricks to enhance your glow at any age. We’ll be featuring editor-tested ...