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UHF radio link between BS2's useing DTMF — Parallax Forums

UHF radio link between BS2's useing DTMF

farmTechfarmTech Posts: 3
edited 2010-04-26 21:05 in BASIC Stamp
I am starting a project in which I plan to use 2 BS2 micro-controllers to remotely control some agricultural irrigation equipment remotely using DTMF tones . I plan to link the BS2’s with a pair of business band UHF Motorola radios to shut down a water pump when the irrigation device is finished. I would like to use DTMF because most of the radios we currently use for voice already have DTMF on the mic.

I have been researching similar projects on the net, but everything I find is pretty dated. I would appreciate any assistance in choosing a DTMF encoder/decoder that is still available. I would also appreciate any assistance in finding some source code to get me started. This is my first micro-controller project so any assistance could be very useful.

I can provide more detailed description of my plan if needed, but right now I need to select and purchase the necessary hardware to get my project started.

Thanks,
Brett

Comments

  • ZuddieZuddie Posts: 5
    edited 2010-04-26 02:17
    It's a little unclear as to what you are doing. If you intend to use the UHF Motorola radio as the transmitter, then it seems you only need a receiver. If this is the case, then you can monitor the incoming DTMF on the common frequency with a BS2 (why would you need a pair?)

    If I am understanding this correctly, then I believe all you would need to decode the DTMF are seven LM567's tuned to the following frequencies:
    IC freq R1
    1 697 15.8 1 2 3 row
    2 770 14.3 4 5 6 row
    3 862 12.8 7 8 9 row
    4 941 11.7 * 0 # row
    5 1209 9.1 1 4 7 * col
    6 1336 8.2 2 5 8 0 col
    7 1477 7.4 3 6 9 # col

    freq is in Hz
    R1 in in k Ohms. use 20K 10 turn trimpots for R1
    R2 4.7k pin 2 to LF common
    R3 20k pin 8 to +5v (output pull up)
    C1 0.10 mfd pin 6 to gnd
    C2 1.0 mfd 6v pin 2 to gnd
    C3 2.2 mfd 6v pin 1 to gnd
    C4 250 mfd 6v LF common to gnd (only need one for entire ckt)
    C5 0.5 mfd pin 3 to gnd

    pin 4 = +5v
    pin 7 = gnd

    You'll need seven of each of the listed components except C4 you will only need one.
    Use seven port pins to read the row and column info to determine the actual key in software.
  • MoskogMoskog Posts: 554
    edited 2010-04-26 05:38
    Hi

    Take a look at this very interesting project by Ken Gracey:

    http://forums.parallax.com/showthread.php?p=759557
  • farmTechfarmTech Posts: 3
    edited 2010-04-26 15:40
    Here are some additional details to help clarify my project;

    The Situation: I have a cable-tow irrigation traveler, which is essentially a really big sprinkler that pulls itself across the field to water the crop. For propulsion, it uses a water-driven impeller to power a wench that winds up the cable. When it gets to the end of the cable, a lever trips and it stops moving but keeps on watering b/c it was designed in the 1960’s. The water is supplied by a nearby well powered by a 100HP 3phase motor. I want to place a BS2 and a radio on this traveler.

    The Minimum: I need this system to at least send an audible tone over our business band UHF radio system so that the irrigation manager will know when it is done.

    Ideally: I would like to place another BS2/radio in an enclosure at the well site so that the well could shut itself down after an hour or so of watering at the end of the run (receiving the tone from the traveler).

    Additionally, it would be a nice feature if I could poll the traveler (from a DTMF voice radio) and have it report the % of completion of the run (which could be measured with a magnetic sensor on the wench). Since my voice radios already have DTMF mics, I thought this would be a good reason to use DTMF.

    However, I am currently exploring options to establish a IP internet connection at the well site, which could mean that I could use the web/text/E-mail to alert the irrigation manager when the run is complete. Thus, the means of communication between the well site and the traveler would not be as important (possibly the RTX-12 Modem suggested by Moskog).

    This is my first project w/ by BS2, I am currently a senior in an electrical engineering technology program eager to put my knowledge to work. However, I have no experience outside of the classroom, so I am seeking the sage advice of seasoned engineers/tinkerers here.
    Thanks, please keep the suggestions coming!!
  • FranklinFranklin Posts: 4,747
    edited 2010-04-26 17:11
    Since you are just starting out I would recommend the Propeller chip as an alternative. It is more powerful and would allow expansion in the future as your project grows (and it will)

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • farmTechfarmTech Posts: 3
    edited 2010-04-26 21:05
    I already own a BS2, taht is why I was leaning that direction, but I will consider the propeller.
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