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Distance and direction detector? Answered

What I want to do is build a device that I can hold in my hand that will notify me (probably with an LED) if I am facing the object I want to find, and preferably how far away I am. I can't use IR because if something is between me and the object I still want to know if I'm facing it
I'm not sure what method I would use but I want to build a device that consists of a transmitter and a handheld receiver, I would probably use radio, and the transmitter would have to be very small, (Keychain sized or smaller preferably). 

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iknowvations (author)2012-07-28

Try looking for long range RFID. It may help you.

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mpilchfamily (author)2012-07-26
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geekman2 (author)mpilchfamily2012-07-26

I have considered gps but gps is accurate within ten feet at best, which is not ideal if I want yo find a small objetct such as keys

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mpilchfamily (author)geekman22012-07-27

Any radio tracking system will be allot less accurate. But now that we know this is for finding keys then you may want to have the receiver on the keys and the remote in your hand. The the remote can trigger and alarm on the keys.

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geekman2 (author)mpilchfamily2012-07-27

I don't want something like the commercial systems where the object makes a sound when triggered, as the sound is easily muffled and you can't use it in a noisy environment

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mpilchfamily (author)geekman22012-07-27

Well if GPS isn't going to be accurate enough for you then a radio tracker isn't either. As you've noted a directional antenna has to be fairly large to get a good fix so its not an ideal solution either way you look at it. The radio trackers are only able to give you a direction. They have no way of narrowing the distance as well as a GPS can. You can get a vague idea of distance based on signal strength but that will only get you within 100 feet of the object. But you also have the problem of finding a GPS locator small enough for a key chain.

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geekman2 (author)mpilchfamily2012-07-27

I don't really need distance and if my keys are outside of 50 feet of me I have another problem altogether. But since you seem to like GPS could you tell me how I might implement a system that makes use of it?

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mpilchfamily (author)geekman22012-07-27

Like i said going the GPS route has its own problems. First is finding a GPS tracker that is small enough. Plus it would cost you a good $100 or more for one. GPS was a better idea before i know you where looking to do a key finder. Unfortunately the best key locator system out there is the kind that emits a sound.

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Re-design (author)2012-07-26

google "radio foxhunting" and you should get an idea of how to do this.

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geekman2 (author)Re-design2012-07-27

That's closer to what I want, but do you know how I might build a handheld directional antenna?, I've looked around but everything I've seen is to large to pull out every time I lose the remote or my keys

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Re-design (author)geekman22012-07-27

Keep looking. I know that some of them are handheld. I don't do foxhunting so I don't have a ready reference for them.

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geekman2 (author)2012-07-27

This is exactly what I want to do but the problem is that the antenna used there is fart to large, making it impossible to use in small spaces. I don't need a range of more than ten feet so range is irrelevant, does anyone know how I might build a miniaturized directional antenna?

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