Mimicking my locating device's 2.4GHz signals

Discussion in 'The Projects Forum' started by hedgehog90, Jul 4, 2015.

  1. hedgehog90

    Thread Starter Member

    Sep 6, 2012
    Hi, I'm new to this, not really much of an electronics/arduino buff so bear with me.

    I want to create something which will do what my store-bought locating device (Loc8tor Plus) does, but I'd like to attach it to the roof of my house and make it operable from indoors.
    Our 2 cats have homing tags on their collars that allows us to locate them and get them in at a certain time. It requires that I go outside looking all around the garden or if I'm lazy, from my windows, but often they're nowhere near the garden, and it sometimes requires several trips outdoors and lots of calling.
    I don't want them staying out past 3-4 when the roads are busy, having lost 2 cats that way. Also, being the Summer, they're prone to staying out as long as they can (didn't get one of them until 5:00 today)
    Also, by placing it on the roof of my house, I have a much better chance of detecting them and I can simply toggle it to search for a tag constantly, while the loc8tor gives up after a few minutes if no signal is detected and requires manual input to retry.

    So far, I've copied the setup from this thread: http://forum.arduino.cc/index.php?topic=54795.0
    I've tested it and it appears to work pretty well, it detects bluetooth signals and the signals from my loc8tor.

    I need to mimic the signal my loc8tor puts out for each tag. They each have a unique signal so my loc8tor can tell which is which, so each tag would have to be registered (ie, have it's unique signal recorded) with my device.
    Then, I need to know what the tag sends upon receiving the message. The tags aren't constantly working, they wait for a signal from the loc8tor, and then they send back a signal.

    I can write a program to interface with the arduino remotely and to render the received data (via wifi probably)
    It won't be as accurate as my loc8tor, but it it would at the very least indicate that the cats are in or near the garden which would be fantastic.

    So, that's my plan... but the problem is I have next to no idea how to do this. I'm a proficient coder, but my knowledge of electronics and RF technology is pretty limited.
    Nevertheless, I'd really like to implement this as it would save me a lot of time and bother, not to mention chuffed to bits with myself for my burgeoning talent in electronic engineering!

    Just to make it clear, all I have right now is a short range nRF24L01 2.4ghz transceiver for testing purposes and an arduino.

    Some help please?
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Does the 24L01 have an output which is proportional to Received Signal Strength (RSSI)? If so, you need to build a directional antenna (Yagi), and arrange to rotate it. By correlating max RSSI with antenna direction, you can get a crude vector to the source of the signal. That presumes that the Arduino can both rotate the antenna, and knows which direction it is pointed.

    Alternatively, you can make an antenna array that is electronically switched (instead of physically rotating). Lots of reading here.

    A crude way is to get four receivers, and mount one low on each of the four walls of the house. Sample the signal from each receiver and start searching on the side of the house with the best signal...

    I routinely participate in Radio Direction Finding Contests, as well as using RDF techniques from the airplane to locate high-altitude research balloon payloads. In a former life, I found several emergency locator beacons on crashed aircraft that resulted in life saving...
    Last edited: Jul 4, 2015
  3. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    @MikeML If an 180• rotation is acceptable then a servo could be controlled by the Arduino, which would know it's position. The Arduino servo library controls the servo motor by degrees. If not, the Arduino can control a stepper motor and track positions by counting the steps c