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I was wondering which technology would be better suited to the goal I am trying to achieve. What I would like to do is embed a chip in an object and by using a cell phone, prompt the chip to send me information on its location.

I know there are chips that are now put in cats to help to track and find them if they are lost. I am trying to find a chip that is very small and light that can help me find it if it gets lost in a maximum 25 foot radius.

Initially I looked into RFID tags for this but cell phones don't have readers in them and the readers are too costly. I have started looking into blue-tooth and have gotten a little befuddled with the details. My education is in medicine, I would very much appreciate any ideas anyone may have.

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    \$\begingroup\$ How large can the embedded device be? Can it contain a battery? If so, how long does it need to last? Do you need to get a direction to the object, or just be told that it is present in a 25 foot radius? \$\endgroup\$
    – Tom Davies
    Aug 13, 2012 at 4:17
  • \$\begingroup\$ Possibly RF becacon , those are used in aviation systems. \$\endgroup\$
    – Standard Sandun
    Aug 13, 2012 at 13:13
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    \$\begingroup\$ AFAIK the chips put in pets are just a type of RFID tag. Unlike the collars used on wildlife they aren't actually trackable over distance, but when someone such as an animal control officer or veterinarian uses a reader they are able to find out information such as how to contact the owner. Since that won't help you, your decisions would be more between devices which can transmit their self-determined position, and devices which transmit a signal on which you can use a direction finder. \$\endgroup\$
    – Chris Stratton
    Aug 13, 2012 at 16:01

2 Answers 2

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I don't know if it will be battery powered and what duration of battery do you need but here are a fe options I have used:

  • NRF24L01 You can modify transmission power and transfer speed to use less power. It is an RF 2.4GHz transceiver, if you wan't to connect to an smartphone It won't be possible.
  • Bluetooth SMD Module - RN-41 It is a very small Bluetooth module so you can connect to an smartphone or PC, it uses about 40mA depending of bit-rate and distance.
  • Bluetooth SMD Module - RN-42 It is the same as RN-41 module above but it has a reduced transmission range (50-60 feets) so it uses less power too and also is cheaper.

If you can tell me more about how you will power the system and the duration of the battery if you will be using one I can think more options :)

About location, please give more information, what precision do you need ? What do you mean by small ? 50 x 50 mm is ok or you need something smaller ?

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  • \$\begingroup\$ How about the location information? \$\endgroup\$
    – stevenvh
    Aug 13, 2012 at 15:10
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What you could try is one of Nordic nRF51822, this is a System on Chip Bluetooth low energy peripheral, an can connect to cellphones that support Bluetooth Smart.

http://www.nordicsemi.com/eng/Products/Bluetooth-R-low-energy/nRF51822

An alternative if you already have a microcontroller is the nRF8001. This chip is a connectivity chip.

There is a third chip, that have the profiles proximity, find me and battery implemented, the nRF8002 (SoC chip). This can be configured to beep or blink depending on what you connect to the IO when you loose the connection to the phone, or when you click to find it on the phone. You can use the chip to make the phone ring as well if you have missplaced the it.

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