Implementing a network of RF receiver/transmitters

Discussion in 'The Projects Forum' started by hedgehog90, Sep 6, 2012.

  1. hedgehog90

    Thread Starter Member

    Sep 6, 2012
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    I should make it clear that I'm not an electronics buff, although I did take Electronics for my A-Levels (and got an A)
    I have 2 cats named Ollie and Tiggy. I don't want them going towards the road for obvious reasons. My house is surrounded mostly by fields, which is where they spend most of their time.

    I currently am using a device called the Loc8tor.
    Unfortunately, it's range is not good enough, so I came up with a solution, involving many radio transmitter/receivers.

    Our house is situated between 2 fields. There are many trees in the hedgerows.
    I would need to build several radio transmitter/receivers, which I can attach to the trees surrounding the fields (the higher, the better).
    Each transmitter/receiver will detect message signals from either the cat's loc8tor tag (attached to their collar) or neighbouring nodes in range.
    It will need to have a range of at least 150m I think. Considering my loc8tor boasts this range (though it doesn't live up to it), it can surely be implemented.

    I could use an Arduino attached to my android phone with an RF receiver. And using my programming skills I could program an app to detect incoming signals from the nodes, and based on number of signals, their locations and the signal strength, I can estimate their position on a map, and using my phone's gps, I can also see where I am relative to the cat's position.
    When I get close enough to the cat to receive their tag's signal on my phone, then I can act as a node, hopefully improving the accuracy of their estimated positions.
    If one of the cats are not detected by any of the receivers, then give me an alert on my phone via the app.

    How would I do any of this? I HAVEN'T THE FOGGIEST!
    I have some experience in programming microcontrollers... but nothing very complex.
    This project would require building a set of programmable receiver/transmitters, connected to replaceable power sources (with some luck though they should last a while, considering my cat's loc8tor tags last months on just 2 tiny 1.5V batteries), programming them so that they broadcast a signal with the cat's location and signal strength, which other nodes can pick up and re-broadcast, effectively acting as signal boosters, and then when the signal contains a message of my cat's whereabouts, using that data via the Arduino data input and my phone's GPS, display the presumed radius of the cat's likely location on an aerial map, along with my position.

    Here is a diagram of what I would I would want to implement:

    [​IMG]

    Could someone please tell me if this is a feasible idea, and if so, please tell me what components and tools I'd require, and finally how I would build one of these receiver/transmitters.

    Here is some reading material for anyone who's interested in helping:
    Arduino for Android: http://android.serverbox.ch/?p=549
    Loc8tor Plus: http://www.loc8tor.com/uk/primary-products/loc8tor-plus-pack.html
    Loc8tor Design Patents: http://www.faqs.org/patents/app/20110012775

    Other info: Loc8tor works at 2.4GHz
     
  2. John P

    AAC Fanatic!

    Oct 14, 2008
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    Keep your cats indoors. It's better for them and much better for the local wildlife.
     
  3. hedgehog90

    Thread Starter Member

    Sep 6, 2012
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    Oh please... PM me if you think I'm a dick for letting my cats out for a few hours every day, but please don't post it on an irrelevant thread about radio frequencies.
     
  4. wayneh

    Expert

    Sep 9, 2010
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    Fascinating project, and thanks for the info on the loc8tor technology (and the great graphic with Ollie and Tiggy!). We get requests on this forum from time to time that this will answer.

    Just one question about the strategy: How does it help to know where the cat is? That alone won't prevent it from darting across the road. I'd think the traditional wireless pet collars that zap the pet when they get out of range would be better for establishing a geofence. Building a defined area of radio coverage for them would be much easier. As long as the cat stays within the desired area, do you really care exactly where it is?

    FWIW, my cats are out all day (if they want) and we haven't lost one to the road in 20 years. It's just a residential road, though, with sparse traffic. We lock them in at night, when the more dangerous beasties roam.
     
  5. BMorse

    Senior Member

    Sep 26, 2009
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  6. MikeML

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  7. hedgehog90

    Thread Starter Member

    Sep 6, 2012
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    Well, I'm in the house most of the day, and when they're out I regularly check where they are with my loc8tor. If they are near the road, I pick them up and take them back. I feel like this is the only way I can stop them going past the road.
    They've been going out for about 9 months now and they haven't ventured to the busy road yet, but they have explored the lane that leads there a bit. Slowly but surely, their adventures have taken them further and further away, to the point where my loc8tor is just good enough.

    I'm pleased to hear that, but as you can probably tell by the nature of my post, these are measures made to prevent what has happened to our cats in the past. That map in the diagram is where I live, it's mostly fields, but we've been unfortunate enough to lose 2 cats over the years due to the nearby road and lane. It was horrible losing our cat Buffy last year. A series of circumstances and realisations converged to make it even worse.

    I know most people wouldn't go to such extreme measures for their cats, but I can't help it. I need to know that they're alright when I let them outside.
    If I could simply look at my phone to see their whereabouts then it would save me a lot of time and worry.


    I've seen them before, but unfortunately they're not sold (or usable) in the UK where I live.
    GPS was originally the plan, but then I'd have to make new tags for the cats, and it would be a struggle to design something small enough for their collars.
    I'd rather keep the very efficient loc8tor tags and use them in my setup.
     
    Last edited: Sep 6, 2012
  8. BMorse

    Senior Member

    Sep 26, 2009
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    Well, that's a bummer..... ok then, your tags are transmitting at 2.4 ghz, at what modulation??..... do you know the protocol these tags transmit the data in? Will you be able to "decode" the info coming from the tags? I am sure this is proprietary information that is not readily available to just anyone... I guess the first thing I would do is get some kind of 2.4Ghz Transceiver module and see if the data can be decoded.... something like this >> https://www.sparkfun.com/products/705 although it only has a 100m range, it should suffice for testing, you may have to find an equivalent module that is available in your area...

    BTW, a new circuit can easily be designed to fit in any space available, it all depends on how well you can work with surface mount devices..... :)

    You should check out Linx Technologies in case you decide to build your own tags for your cats.... they have some narrow band transceivers that can get better range than the 2.4ghz ones, I use a few of their products in some of my projects and with some modules I can get 3000+ ft range @ 433Mhz....
     
    Last edited: Sep 6, 2012
  9. hedgehog90

    Thread Starter Member

    Sep 6, 2012
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    CTRL+F "protocol" in loc8tor design patents:

    Using a specification based on the IEEE 802.15.4 standard, the first and second communication modules may have a maximum range of between 100 m and 200 m. For example, the first and second communication modules may have a maximum range of between 125 m and 175 m. However, it is conceivable that other suitable protocols (e.g., ZigBee.® or Bluetooth) may be used to implement the present invention.

    I will look into this. Although looking at some of the Linx modules, I don't see how I would attach them to my cats without some sort of harness :)
     
  10. BMorse

    Senior Member

    Sep 26, 2009
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    The patent only says that other protocols such as zigbee or bluetooth can be used, it does not specifically say what protocol they are using now...

    Well, you would have to build it into an enclosure that you can attach to their collar...:rolleyes:
     
  11. wayneh

    Expert

    Sep 9, 2010
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    The commercial pet containment systems could accomplish that. Not as cool as seeing where they are, but it is a cheap(er) option.
     
  12. hedgehog90

    Thread Starter Member

    Sep 6, 2012
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    Sorry, this just isn't an option.

    For now, let's make this simple:
    Lets suppose I want to make a tag for 1 of my cats consisting of a transmitter (and possibly a receiver too, to tell the transmitter when to start transmitting which would be much more efficient), and a receiver attached to an arduino attached to my phone, RF at 433MHz with a range of 300m. And consider that the cat's tag is operating off 2 LR44 1.5V batteries.

    Can I make anything small enough that will send a dumb signal to my arduino-receiver-phone thing?
    The cat's transmitter only need to broadcast their ID, Ollie or Tiggy.

    The receiver attached to my phone should pick up the signal when within 300m, and then it needs to very basically decode the signal for the ID and get the signal strength.

    I understand that this won't be directional like the Loc8tor, but with atleast 3 nodes it will be quite accurate in telling me their position.

    Anyway, for now, let's just imagine that this is all I want to do. 1 transmitter, 1 receiver.
    What would I need to build this, and how would I build this. Please be detailed.

    I appreciate all the other suggestions and all of your help, but I really just want to know how I would do this exactly. It can be improved upon later.
    Thanks.
     
  13. wayneh

    Expert

    Sep 9, 2010
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    It makes sense to me to continue using the loc8tor transmitters, to avoid having to build such a thing, which I think would be challenging. You "just" need a receiver that can see them, output signal strength, and a way to tell one tag from the other, right?

    Actually, do you really need to tell them apart? I mean, if one gets near the road, I guess you'd run out with your loc8ator receiver and soon know which one you are trying to corral?

    Changing the subject, have you contacted the company for help? They might be able to offer some ideas.
     
  14. BMorse

    Senior Member

    Sep 26, 2009
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    you could still build your own pretty easily (Thats if you have experience with microcontrollers, an Arduino would be too big to strap to the cats) You could get a low pin count (8 pin) microcontroller (Microchip Pic's are plentiful), and one of these >> http://www.rentron.com/remote_control/TXLC-XXX-LR.htm which could both run on a CR2032 3V Coin Cell battery, just program the pic (or whatever uC you choose) to "wake" up every couple of seconds (or sooner) to just send out the cats "name", then have it go back to "sleep" or low power mode to conserve battery power....

    Then on the receiver side (your phone + arduino phone thingy) can connect to one of these >> http://www.rentron.com/remote_control/RXLC-434LR.htm, if you make use of the RSSI (received signal strength indicator) you can probably make a pretty good estimation on how far they are from the receiver...... If you end up going with this idea, you can build multiple Transmitter/Receiver modules (or just use one transceiver such as this http://www.linxtechnologies.com/en/products/modules/lt-rf-transceiver to receive and "rebroadcast" the data) placed around the perimeter of the boundaries and by using the RSSI, you could triangulate the location of the cats......
     
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  15. hedgehog90

    Thread Starter Member

    Sep 6, 2012
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    Considering they don't release this information in the patent I doubt they would tell me if I asked politely. Besides, I've changed my mind. I'd rather have a go at making a tag myself.
    I found this guy on youtube that gives me confidence: http://www.youtube.com/user/dazaro3
    I've emailed him to see if he can help me.
     
  16. BMorse

    Senior Member

    Sep 26, 2009
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    You do realize these are FM audio transmitters designed to be used with FM radio receivers? And that he is promoting those products on his site which are kits or modules that are for sale....
     
  17. hedgehog90

    Thread Starter Member

    Sep 6, 2012
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    Yes I do, but some of the transmitters he's designed have a range of up to 1km, and they're tiny. Which is ideal for me. Only difference is that mine will have to run from a smaller power supply, a different frequency and instead of sound they'll be sending raw data signals.


    This is exactly what I want to do for now. However I think 3000ft is a bit overkill. I think 1000ft is fine. Should be cheaper and more efficient.
    Could you give me some detailed instructions on how I would put this all together?
    Exactly what tools and what components. I am a newb.
     
    Last edited: Sep 7, 2012
  18. hedgehog90

    Thread Starter Member

    Sep 6, 2012
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    I've ordered some basic stuff from ebay:
    Some pcb stripboards
    A better soldering iron
    5 x PIC12F683-I/P
    PIC Programmer

    I haven't got an arduino and I haven't bought any components (apart from the PICs), because at this point that would be silly.

    I've been looking around for tranceivers, and I would guess that the TRM-433-LT will do the job best. It's very small, efficient and apparently easy to operate. It boasts and incredible range, almost 1km.
    http://www.linxtechnologies.com/en/products/modules/lt-rf-transceiver

    If that's no lie, I'd be interested in getting a GPS to work with it.
    That way, I only need 3 transceivers (2 for each cat, 1 for me), 2 GPS modules & 1 arduino. Relatively simple.

    All I need is some more advice and a helpful hand to take me through the process of putting it together.
    I will be chuffed to bits if I can make something better than the Loc8tor :)
     
  19. BMorse

    Senior Member

    Sep 26, 2009
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    Well, to start off, you will need to have a Microcontroller (any 8 pin pic would do), a way to program the microcontroller ( a pickit2 or a pickit 3 would be nice, stay away from cheap clones!), and a way to write the program for the Microcontroller (download MPLAB from Microchip, use Hi-Tech C Ver 9.83 for the compiler (Lite version is free, with a few limitations that should not matter for what you are doing))


    and a pair of the Linx RF Modules....

    I am going to order some sample microcontrollers from Microchip (Pic12F629's and Pic12F675's) I already have an extra pair of the Linx modules (TXM-433-LC-R, and an RXM-433-LC-S) on hand... I am gonna try to put together something that you could use as a guide to do your own (one advantage I may have is that I have my own CNC Mill for making circuit boards, so it's really not a big deal for me to whip the whole thing up in a weekends worth of time). I think the biggest part of the whole cat tag would be the 3V CR2302 coin cell battery :)
     
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  20. BMorse

    Senior Member

    Sep 26, 2009
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    Update:
    Just placed sample orders for both mentioned Microcontrollers....
    Have preliminary Schematic and PCB done for Cat Tag Transmitter (or CATT) (size is 1.25"x.95" with Battery) ... (see attachments)... will have to do a "soft" UART for the serial transmission since these Pic's do not have built in UART.

    Cat Tag.png
    Cat Tag Sch.png

    One thing that did dawn on me while doing all this.... Triangulation, we do not have a way to tell "where" the Tag will be transmitting from, without having multiple Transmitter/Receiver's laid out around the perimeter, we will not be able to determine the tags location... have some pondering to do...
     
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