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My wife lost her keys, I'm hacking a key pager together. It's working . . . sorta.

I was thinking: 1)An old cordless phone with a pager function I could hack apart and reuse. 2)An old cellphone for the same purpose. 3)A crystal radio learning kit. My goal is to do this for under $40--the cost of buying that way overpriced pager system you've seen advertised--and for me to learn while doing this. After reading another instructable, I was inspired to use a cheap radio controlled car.

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trebuchet0310 years ago
My parents have the same problem with keys, remotes, etc. etc.

It totally goes against a personal sense of DIY and personal experience.... Over the holidays, not able to figure out what to get for my mother, I came across an 8 device pager thingermabob. It was the first, and likely last item I bought from The Sharper Image. My mother is the hardest person to give a gift to (the right type of course) -- and that's a capitol HARD.

The cost was $50 (shhh don't tell her) and she probably uses it 7 times a week. So at 5 minutes saved per use - that's over 30 hours a year! So even at minimum wage - it pays for itself quickly...


So from my experience with this, I'll give it a high score because it does 8 times more devices than what I would have made -- and it won't eat batteries like something I would have made :/

I know it doesn't help on how to make one... I'm just sharing our experience ;)
I looked on The Sharper Image website and didn't find what you're describing. Can you give me some more details, name, part number? Thanks!
royalestel (author)  trebuchet0310 years ago
Well it's good to know the thing isn't a rip-off . . . but I'm still making my own. I want to learn, for one thing. And, um, $50 is still a lot of money. Besides, I only need one for her set of keys. Thanks for the memories, though :) Any idea which source might work better than another?
Ed6510 years ago
This is strictly a visual device so it may not suit your needs but it's a neat idea anyway. See http://devan.sensoryengineering.net or search for "LED marker beacon". This circuit uses a blinking LED plus a couple of othe components and turns itself on after dark. It looks to be small enough to put on a keychain.
royalestel (author)  Ed6510 years ago
Yeah, that's probably not really going to work for my wife. Actually, I received a sample self-driving beeper in the mail last Thursday. I hooked it together and got it working and then fried it with ESD by not being careful. I'm a bit depressed about that.
royalestel (author) 10 years ago
Okay, I've kind of got this thing working. I reverse engineered an RC car receiver and figured out a good point to hook up a piezo speaker. The transmitter is in the 27Mhz band, but I had a hunch that there might be a lower frequency harmonic that the piezo would respond to. I hooked up the piezo, and sure enough, there was a faint beeping. Great! That's some progress. However, I need a LOUD beeping for this to be a useful key finder. In the first picture, the parts in red show how I hooked up the piezo speaker. It occured to me that maybe I could amplify the signal with a transistor and that would mean a louder beep. So I tried to hook up a transistor as seen in picture 2. That didn't work at all. Not even a faint beep. Now I'm stumped. Anybody have a simple idea of what I could do to make the beeping of the piezo louder or what I'm doing wrong here?
receiverschematic.JPGreceiverampschematic.JPG
dogsrcool2me10 years ago
I too have looked around for a device that I can bult like this but can't find plans. Any ideas?
royalestel (author)  dogsrcool2me10 years ago
at this point I think I'm going to try to chop up an old RC car.