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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.
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Previous "Gadget Freaks" - Link.
You can get these for around $17 pre-made (Google or eBay "laser car parking"). Some use solar cells mounted next to the opener light bulb to provide power and to turn the pointer on/off with the opener light. Depending on where you buy your parts, a pre-made unit might be cheaper.
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Egad. Why do this the hard way?
My dad made one of these not too long ago, and avoided the entire diode/relay construction. There's already a relay in the garage door light itself, and the light is a standard edison socket, so you just go to your local hardware store and get a splitter that gives you one two prong plug and another edison socket. Put that in the light socket, put the light back in, attach a wall wart to the two prong outlet, adn attach that to the laser, mounted appropriately. All the fiddling with a solar cell or relays is quite unnecessary.
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Good idea. A solar cell would be easiest though as there would be no need for the wart at all since you can direct connect the solar cell to the pointer and expose the cell to the light bulb and DONE!. The cells in those $5 solar yard lights that you can get at Harbor Freight put out about 3V.
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Modifying a laser level will give you a stripe of light that you can use to back a large vehicle into a small space with limited mirror visibility. Similarly, making a clip to carry a pointer on the vehicle will allow you to back it up precisely, so long as you can see the target dot in a mirror somewhere.
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You might not have noticed, but they do it the complicated way because it's in Design news. I,e, they have to get the sponsors paid with everyone buying their electronic components from Allied, Digikey or Mouser. I'm sure there are tons of other easier ways, they just want you to spend money.
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