APRS

APRS tracker with DRA818V

53 commentaires

Small prototype of combination between trackuino and DRA818V,

Overview

« Trackuino is intended for use by licensed radio amateurs. By operating on the standard APRS frequency, the signal can be picked up by an Internet gateway and reported on aprs.fi, so anyone with an Internet connection can track the tracker »

The idea of this project was to build a trackuino board with small gps module, low power arduino pro mini (3.3v @8mhz), a VHF transceiver DRA818V, and power management integrated. vue-dessus-dra818v_2with_antenna

µC:  The Arduino pro mini is intentionally clocked to 8mhz to ensure a less power consumption. Trackuino code was modified to send data to the VHF module, a resistors divider provide voltage batterie monitoring, and a LM60, the global board temperature. PTT on pin 10, Wakup/Sleep mode control on pin 11, and APRS audio modulation, pin 9,  with a capacitor link and adjustable resistor (100k).

GPS: is a 4D Systems | GPS-PA6B (16x16mm!), Enable pin is wired to a MOSFET, for a futur power management control function (pin 2 of Arduino).

Radio: Ensured by a Chinese TRX DRA818V VHF module, power output is selectable between 500mw/1W, the module is drives by a UART communication bus on pin 7/12 from Arduino. also, he provide a Power saving control mode. I have put a low pass filter from minicircuit to avoid spurious modulation, the antenna is a 169Mhz version from Lextronic on a SMA connector. All of component are powered under 3.7v.

Dimension are 80x56mm. Weight 78g.

vue-dessus-dra818v

Power: A batteries from smartphone provide 3.7v@1450Mah, and can be charged with a dedicated chip, LTC4054.

power

Trackuino modified source code can be download here.

Schematic is here. Fell free to improve it.

If you are a licensed radio amateur you can use this @30db power on VHF APRS band 144.800, 144.390. If you are not, the ISM European 169mhz is open @27db max power output with 1% duty-cycle without licence. Be carreful to respect your local laws.

 

53 réflexions sur « APRS tracker with DRA818V »

  1. excellent do you have any fritzing schetc?

    Also if you are transimiting something in this specific frequensy , everybody in this freq can listen your data?
    what if someone got two of these moduiles
    TX and RX and TX send Long,Lat. and only the specific RX wants to get those data ? can this be done , or you have to make some kind of encryption between those Server and Client machines?

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    1. excellent do you have any fritzing schetc?
      – NO, no needed in fact.

      Also if you are transmitting something in this specific frequency , everybody in this freq can listen your data?
      – YES, since is APRS

      what if someone got two of these modules TX and RX and TX send Long,Lat. and only the specific RX wants to get those data ? can this be done , or you have to make some kind of encryption between those Server and Client machines?
      – You can implement an encryption, as you want of course, but it’s not required, since is TRX modules, you can send long,lat with one module and receive with another in same frequency, sensitivity is -122db

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      1. The amateur license in the US which is required to transmit in the 2 meter band (144 MHz) forbids encryption. The FCC has been so far unwilling to bend on that though a number of amateurs have made requests to add encryption to the rules for VHF/UHF.

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  2. hi
    where do you define the gps object? I got an error in line 122 ( gps.encode(Serial.read()); ) —>gps was not declared in this scope

    regards
    /alex

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    1. Hello. What is the version of arduino IDE you use ? Code need to be compiled with v1 if i remember. I will check when i back to home next week.

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      1. Hi

        I’m interested in using your project for HAB research. I was wondering if you have a more comprehensive parts list. More specifically, where did you purchase your optocoupler and what diodes are you using?

        Regards
        Margaret

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  3. hi,
    I actually use 1.6.8 on Mac, I have tried also 1.0.5 on Mac with another error (undefined reference to setup/loop)
    which version of 1.x have you used?

    regards
    /alex

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    1. I have renamed the scatch and the folder to trackuino (without the version number in it) an get the old error (gps was not declared in this scope…) with ice 1.0.5

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  5. Hi

    I’m interested in using your project for HAB research. I was wondering if you have a more comprehensive parts list. More specifically, where did you purchase your optocoupler and what diodes are you using?

    Regards
    Margaret

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      1. What do you mean generic optocoupler? If I were to buy one from mouser, what type of requirements do I need? Sorry to be so lame, but I’m new at this.

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  8. I’m planning to use this project as a starting point to something bigger. Similar to what has been posted on the ARRL website, I’m going to try and sort out how to use the APRS system to remote control a small robotic platform by sending commands to it as « One-liner » messages. Obviously, I haven’t yet worked out what needs to be changed in the code for this tracker to recognize those one line messages and interpret them as commands. Do you have any ideas there? If you are still actively working on this project, perhaps we can exchange email on the subject?

    Thank you for putting this online.
    KG7WPQ

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  9. Hello Weird Lab,

    Thanks for this informative post. I am currently also trying to learn about the DRA818V module, and using it in combination with a 3.3V Atmega microcontroller.

    There are a few points that I currently don’t understand – which isn’t that surprising, given that I am pretty much a novice in this field. Perhaps you, or someone else who comes across this comment could try to explain. This would be greatly apprechiated!

    * the PTT transistor: is the external transistor just there as a « convenience », to invert the signal from the microcontroller and make it default to receive? Or is there any other value to it? (e.g. driving the PTT pin with more current?)

    * the PD optocoupler: you mention above that this works, but other people also use resistor dividers … I am curious as to why? What happens when one connects it simply to an output of the microcontroller and drive it high or low? (Is the radio module sinking current through the microcontroller when PD is low?)

    * the passives between the audio pin and the microphone input: at the end the voltage should be about 100 mV peak-to-peak for the radio, am I right? What values (or ratios) did you end up using for your 100kOhm trimpot at the end?

    I have also seem designs where the coupling capacitor is at the other end, right at the microphone in. Does this make a difference?

    Thanks a lot, with kind regards
    gohai

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    1. Hello,

      Sadly, the datasheet do not provide a lot of information’s …

      – to switch to « Transmitting » mode, Tx, you just need to put PTT pin to ground, by default if you leave this pin floated, the DRA818 will be in RX mode.
      – yes other people also use resistor dividers, but in my case it was unstable
      – for your last question is depending of kind of modulation or bandwidth desired, i have used a 100k to adjust as better the quality of modulation.

      keep in mind it’s a very cheap TRX, and after testing a lot of , its not the same quality for all product, (as always with Chinese and cheap product).
      so, the way is to made a prototyp

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  10. Hi,
    Is it possible connect audio output from pin 3 DRA818V to my small Raspberry PI with USB sound card to decode APRS frames when TX not transmit using your solution ???

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      1. Thank you for replay.

        I don’t have LM60 sensor but I have very popular sensor DS18B20. Can I use this sensor instead LM60 without modify code ??

        73 Waldek

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    1. yes it will work, but you need to change the scale factor in the code, (if i remember, around sensor_avr.cpp)
      Linear Scale Factor is 6.25 mV/°C for LM60, AND 10 mV/°C for TMP36
      (LM60 can be get from Ti for SAMPLE, then you can test before buying some on ebay … or not)

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      1. Hi,

        Many thanks for suggestion and advise to request free sample for TI LM60. I have register on TI but it is look I can request free sample because IT send free sample only for a corporate (.com) email 🙁 but I don’t have corporate email which have on end .com

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        1. I have found in sensor_avr.cpp formula where is used scalar for LM60

          case 1: // C
          // Vo(mV) = (6.25*T) + 424 -> T = (Vo – 424) * 100 / 625
          return (4L * (mV – 424) / 25) + CALIBRATION_VAL;

          for TMP36 should be ???:

          case 1: // C
          // Vo(mV) = (10*T) + 424 -> T = (Vo – 424)/ 10
          return ((mV – 424) / 10) + CALIBRATION_VAL;

          I am not sure that we need return temperature in Integer Constants and we need use for example:

          case 1: // C
          // Vo(mV) = (10*T) + 424 -> T = (Vo – 424)*10/ 100
          return (10L*(mV – 424) / 100) + CALIBRATION_VAL;

          73 Waldek

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  12. Hi Weird Lab

    I have collected all parts and start with build your construction. I will be use TMP36 instead LM60 and I will be use opto-coupler 4N25. But I have review your schematic and photo I have see that you are use 2 resistors with PC817. What kind/ value resistors your are use ?

    73 Waldek

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    1. you can use what you want of GPS module, just ensure you use the good baud-rate.
      you can connect the opto directly to Vcc, in my case i use 0 ohm resistor to Vcc because it was a strap.

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  15. Hi,

    I’m upload the code my Arduino Nano.
    But, doesn’t work. trackuino1.51_rev2.ino

    Before I upload checked the code with Arduino IDE, don’t give error or warning message.

    And of course I setting up the conf.h

    When uploaded not error massege.

    It does not do anything.

    I connected one LED to PTT and one to GPS power port.

    The LED lighting on inmediately When finished program upload or press reset button on the Arduino.

    The RX LED flicking on Arduino when GPS modul send GGA messages.

    The GPS is fixed.

    Thank you any idea.

    Tony

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  17. Ping : APRS Tracker, with SmartBeaconing – F4HUY

  19. Thank you, I missed it in the main code. I thought it might be in the radio lib. or the config.
    A very nice project, I have it working hard wired to my Igate now to make the radio module transmit.
    I would like the transmitter only transmit 20 or so mw, Guess I need to go inside the module and see what’s there.
    Thanks again.
    Cheers,
    Doug k6sts

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  20. I made a couple of these but could never make them work right.
    The unit transmits APRS to my radio but the range is LOUSY (a couple of feet!!). I suspect there is a problem with the DRA818V module. I got mine from ebay from some China vendor. Perhaps they were selling modules that were not working right.
    Another one of the units I can barely hear the APRS on the radio.

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    1. – what is the voltage level of your unit ? with low voltage, don’t expect 30dbm out, so a very long range
      – you need a perfect antenna match, and fine tuned for 145mhz
      – low pass filter do -1db att
      – signal is weak, you need a receiver system with a good antenna on a high point
      Many other thing can affect transmit and receiv, in mobile i prefer to use my 8w unit, it’s work in all situation http://www.f4huy.fr/?p=1122

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  21. Hello, i have a short question. Why needs the DRA818 TXD Pin 3,3Volt and not the RXD Pin? In my understanding TXD is transmitting Data from the DRA818 and RXD is receiving Data to the DRA818. When i use 5V Atmega, i think there should be a voltage devider for 3,3Volt to the RXD DRAs RXD Pin where the TTL levels on the DRA818 are 3,3Volt.

    //////////////////////////
    #define PwDw 11 // Power Down pin. This need to start low, then be set high before programming.
    #define DRA_RXD 7 // The Arduino IO line that is connected to the DRA818’s TXD pin. 3.3V only
    #define DRA_TXD 12 // The Arduino IO line connected to the DRA818’s RXD pin.
    SoftwareSerial dra_serial(DRA_RXD, DRA_TXD); //for DRA818
    //////////////////////////

    Thanks, Andreas

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  22. Hello can we listen Ais data with this module 161.975 MHz
    Output format nmea0183
    But ı think when we receive audio it must be pass from gmsk.do you have experience with that ?

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    1. Hi, DRA818V can run from 134 to 174MHz, so, I can say yes. I think you can try to listen with squelch opened,
      may need a LNA and band pass filter in front

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  23. Ping : APRS Tracker, with DRA818V – F4HUY

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