Short distance tracking device

[Fluster]

Hi,

I've been interested for some time now about an idea to implement a small device that I could find with a cell phone application from short distance. The ultimate goal would be a small device that I could attach e.g. on items that get easily misplaced outdoors, when I could activate a search on my cell phone application for a specific item and see how far I am of it. To reach that I would of course need a lot of product development to get the device small and handy enough, but at this point I'm also interested on simply experimenting with the idea.

To find misplaced items from a relatively small search area I think the minimum requirements would be that I could get a signal from at least some 10 meters distance and accuracy of a couple of meters. In that case I could walk around the search area until I get a signal and then approach the signal until at a couple meters away I should be able to find it. Since the idea would be to keep the device attached to items all the time and use the search when needed, I would need a long battery life, which means that the device should be passive for most of the time and only answer when called by the cell phone application.

My idea of the principle how the device could work would be that it is normally passive, but when it receives a radio signal of a certain fixed frequency, it immediately responds to it. In that case the search application could simply keep sending a signal and if it receives an answer, calculate the delay to find the distance. I'm not sure how accurate delay measuring it would be possible to reach with a cell phone, but at this point I'm mostly interested of the target device (Programming is more my home ground than electronics, so I'm not worried about that so much). The technical requirements when using this approach would be (if I'm not mistaken) that the frequency of the device should be fixed on a small range (when there could be multiple devices with different frequencies) and that the structure of the call and response signals should differ enough to prevent false echoes.

I have not built anything like this before and I don't know about electronics that much, so I'm hoping that someone could comment on if my design idea is completely off or if not, point me to the right direction on where to start. I expect that this kind of device would be simple enough that there would already be (a lot of) existing devices and resources on how to build them in the Internet, but I at least haven't been able to find the right search words for them. Using Google I keep bumping on RFIDs and active transmitters, but none of them sound like to fit for my needs.

So in short: I'd like to build a device that sends a fixed radio signal when it receives another fixed radio signal. It should not use battery when passive and the signal should be readable with a cell phone from at least 10 meters away.

 

[Inquisitive]

Google "find lost items with your phone app"

Think there is a product out there. That will do the trick.

Unless you want to build your own.

 

[MikeMl]

If the remote object has turned off its receiver to save battery power, how does it know you are looking for it?
How does the remote object know where it is to tell your phone?

 

[Fluster]

Google "find lost items with your phone app"

Think there is a product out there. That will do the trick.

Unless you want to build your own.

Even though simple, those were better search words than any of what I could came up with (never been good in inventing good search words). Iexpected someone already has some products like this. Thank you.

However, viewing the products available it doesn't seem that my original problem is fully solved with them. To enlighten my idea further I have been trying to find a way to find my disc golf discs when they get lost on a track. In that sport it is typical that after an unsuccessful throw the disc may fly out of the track and sight when the search area may be a few hundred square meters. While on most of the cases the disc is found easily, sometimes depending on the terrain and how the disc has landed finding it can prove to be very hard and many times I have given up after 30 minutes or even longer time. The problem is clear on rocky terrains and near water, but sometimes the disc can almost supernaturally dig itself to seamingly simple field of long grass so that you can step on it without finding it. My goal would be to save not only money, but also time, if I could locate my discs more easily.

In this scenario there is two main problems compared to the products on the market - the tag cost and the tag size. Both of them are such problems that I would like to first understand what kind of components the device would require so that I could even estimate if they are possible to solve. The size problem is that since the tag should not affect the flight properties of the disc too much, it would either to be a very thin sticker or to be embedded into the disc (which would still mean very thin). This means that any hard cover is out of the question and practically the components should be for example placed in between two paper stickers. And what comes to pricing, an average disc itself costs roughly $15 and a player has dozens of them, so the products with tag cost over $20 are not a solution. All the products on the market seem to have properties that exceed my needs (internet, GPS, buzzers, long ranges etc) so I'm wondering if the size and cost could be pushed by stripping the properties to the absolute minimum.

I originally got the idea after seeing some electronic prize tags (electronic paper) that seemed to have lot of the features I would also need: thin as cardboard, cost of a few dollars per tag, an antenna to receive information and years of battery life (and even a screen that I don't need). This made me think that maybe the device I'm after could also be possible.

 

[Inquisitive]

Radio Frequency Identification (RFID) tags are thin. But the scanner would not have the range you seek. That rules that out.
Strobe lights would not be bright enough during the day.
Radio beacon collars that are used in wildlife management have bigger transmitters than would probably work here, again most likely too big, too heavy. Then there is the cost of said components and receivers. Not cost effective per unit.

"I have not failed. I've just found 10,000 ways that won't work."

Thomas A. Edison


Keep digging, wish you well.