This circuit can be used to test up to three LEDs at once, connected in series. You can easily increase that number by using a higher supply voltage. If you do so, you should allow 2.7 V for each ...

High-brightness LEDs, with independent delay and duration, find use in a visual-inspection application. This circuit is not complex, but it saved the day in an application involving visual inspection ...

Signals when an on-circuit battery is exhausted, 5V to 12V operating voltage A Battery-status Indicator circuit can be useful, mainly to monitor portable Test-gear instruments and similar devices. LED ...

This article was taken from the November 2012 issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content by ...