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Re: Questions about T3mini and GT-320FW GPS

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  • Will
    An update - Well Silly me, the voltage drop seen at the 5V pin is caused by the isolation diode D2 dropping about .45 volts. The regulator output is spot on 5
    Message 1 of 5 , Jul 16, 2013
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      An update -

      Well Silly me, the voltage drop seen at the 5V pin is caused by the isolation diode D2 dropping about .45 volts. The regulator output is spot on 5 Volts prior to the diode.

      The tracker and GPS are drawing 90ma at 8.9 volts which seems high. There is still a lot of heat generated at U1 the voltage regulator. To reduce the power loss, I think the only solution would be to remove U1 and replace the circuit with a VR that is better suited for higher input voltages, something like a LK112SM50.

      I am still unable to get the GPS unit to send usable data on the TTL Out line.

      I hate to say it, but I think I will need to scrap this hardware and replace it with the other companies SMT tracker. The feature set of the T3-Mini are awesome, but the power draw is too great and the GPS... well I don't think I know what to say about it.. I know the other set up works as my first tracker was based on it and it works fine, just a little more expensize.

      Will - N7IPY
    • Marcel S
      Willy, A few comments: - You should be using the RS232 output on the GPS for the argent products. See:
      Message 2 of 5 , Jul 16, 2013
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        Willy,

        A few comments:

        - You should be using the RS232 output on the GPS for the argent products.
        See: https://www.argentdata.com/catalog/product_info.php?products_id=144 Be
        sure to use the correct cable pinouts from the GPS and try again. Hopefully
        that will solve the GPS part of the problem.

        - The currents you are reporting seem to be ballpark ok. The OT3m normally
        draws 40mA (so I presume the mini is in the same range (I don't have one
        here to check)). The GPS will draw <45mA (
        http://www.argentdata.com/files/GT-320FW.pdf) so the 90mA you are reporting
        doesn't seem far off from what you would expect. Keep in mind the 78L05UA
        regulator in use maxes out at 100mA, so if you're measuring the 90mA on the
        input, then there is a good chance it's being overdriven. You might want to
        check the GPS current inline and double check your wiring in case something
        is shorting and causing the regulator to max out. That regulator is
        designed to handle the tracker plus a GPS puck.

        I hope this helps out a bit. Keep us posted with your progress!

        Cheers,

        -Marcel AI6MS

        On Tue, Jul 16, 2013 at 7:39 AM, Will <engineer1@...> wrote:

        > **
        >
        >
        > An update -
        >
        > Well Silly me, the voltage drop seen at the 5V pin is caused by the
        > isolation diode D2 dropping about .45 volts. The regulator output is spot
        > on 5 Volts prior to the diode.
        >
        > The tracker and GPS are drawing 90ma at 8.9 volts which seems high. There
        > is still a lot of heat generated at U1 the voltage regulator. To reduce the
        > power loss, I think the only solution would be to remove U1 and replace the
        > circuit with a VR that is better suited for higher input voltages,
        > something like a LK112SM50.
        >
        > I am still unable to get the GPS unit to send usable data on the TTL Out
        > line.
        >
        > I hate to say it, but I think I will need to scrap this hardware and
        > replace it with the other companies SMT tracker. The feature set of the
        > T3-Mini are awesome, but the power draw is too great and the GPS... well I
        > don't think I know what to say about it.. I know the other set up works as
        > my first tracker was based on it and it works fine, just a little more
        > expensize.
        >
        > Will - N7IPY
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