Keychain IR beacon

What do you think about a IR beacon on a keychain that flashes every 10 secs or so while its not moving. (And optionally flash brightly before going into energy saving mode turns when touched) essentially you can use your mobile phone to locate your keys when lost.

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You know of those keychain-finder devices, where you clap or whistle and they respond with a beep so you can find them?  Find some way to replace the speaker with an IR LED ( or just tie in the IR LED so you have both visual and audible locating.)
whatsisface9 years ago
That would be pretty cool... I'm thinking it could be done either with a microcontroller or with 2 555 timers, one in monostable and one in astable, a vibration switch as a trigger and a couple of IR LED's as the source of IR.
That is what irritates me about the LED flasher ic becoming nearly extinct. It used so much less current then the 555 *sigh*
Ah you mean the good old transistor and cap ones, I used them loads in school as 555's were pretty scarce and I still think that overall they're a better circuit that seems to screw up about 90% less than 555's in ameteur circuit building, also they can drive more LED's than an IC and it's a pretty compact circuit. not tiny but good.
Well, I was referring to the LM3909 really. It was a really cool (hobbyist) useful IC, but industry demands were kind of low.
Oh right, well we did used to have a fair few of them kicking about the school but they were rarely used because the techie knew they were in short supplies so he refused to let us have them.
Yeah, back when I had opportunity to get a few hundred, I should have......sell em for $10 a piece now LOL. I wouldn't REALLY do that, but they WOULD be handy to have around
akimbo m (author)  Goodhart9 years ago
http://www1.jaycar.com.au/images_uploaded/LM3909.PDF

I think reading this schematic, you can build your own version. Might be cheaper and smaller too?
I can't work with surface mount stuff, but even so, fitting all that into the space of an 8 pin DIP IC would be difficult and getting the specs just right might be cumbersome. But, on the plus side, you could fine tune it the way you wanted to. :-)
there are transistor driven led flasher circuits out there.
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