Here’s the latest “Gadget Freak” – how to build a garage door locator device so you don’t damage your car – “Not satisfied with the low-tech method of suspending a tennis ball from a string, Ken Swanstrom devised a better garage locator device from a laser pointer. This simple circuit is powered by a 6V dc wall wort, adjusting the output to yield 3V dc as a substitute for battery power. A CdS cell “looks” at the garage door opener light and actuates a relay, turning on the laser pointer when the garage door opens. And voila no risk of front-end damage anymore.” – Link.
Previous “Gadget Freaks” – Link.