My GPS transmitter winter project

Discussion in 'Rocketry Electronics and Software' started by RKeller, Mar 3, 2019.

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  1. Mar 3, 2019 #1

    RKeller

    RKeller

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    I'm a big fan of Eggtimer products, I have several quark altimeters I use frequently and a bunch of eggfinders (5 I think including mini's and TRS's), I use one in nearly every flight. Big thanks to Cris for supplying such great products at great prices!

    But... I also love to tinker with things and can't leave well enough alone. I got this idea in my head to make my own transmitter. I wanted a transmitter with an integrated battery, USB charger, and a small enough size it would fit in most rockets.

    This is what I came up with.
    [​IMG]
    I just put it together last week and started testing stuff, but I was pleasantly surprised when it fired up, got a GPS lock and started transmitting GPS data. YAY! It works with my existing Eggfinder receivers as expected too! It uses the same transmitter module as the eggfinder and the same method of operation, it's simple and it works well. I did try out a new type of GPS module with a teeny tiny chip antenna. I was worried about that but it seems to perform really well so far.
    Here are the details
    - 16mm x 76mm PCB, about 10mm thick complete with battery and OpenLog (fits inside 18mm tube)
    - Push button on/off that requires a 1sec hold to prevent accidental presses.
    - integrated 300mah 1S lipo (~2.5 hour runtime)
    - integrated USB charger with LED's (green charging/red done)
    - blue power LED cuz I love blue LED's.
    - Orange 3D Fix LED, steady on when there is a 3D fix.
    - OpenLog micro SD card for logging flight data.
    - RP-SMA antenna mount, or wire antenna.
    - backup power to GPS module to remember previous satellites for quick lock
    - Off state current should be under 16 micro amps so it won't drain the battery when its off.

    I have some connectors coming for the battery, a stubby antenna, and some clear shrink tube to go over everything. already have a list of things to fix if I make more PCB's lol.

    [​IMG]
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    Last edited: Mar 3, 2019
    PhysicsGuy, Zertyme, DGBrown and 2 others like this.
  2. Mar 3, 2019 #2

    Locksmith

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    nice work, good luck on your testing and keep us posted.
     
  3. Mar 3, 2019 #3

    SpaceManMat

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    Very nice. A few questions, what is the weight and the GPS chip? Also cost?

    While the all in features are nice I’d be looking to offload the charging and power button cuircuits to save weight and size.
     
  4. Mar 3, 2019 #4

    tfish

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    Nut Finder...funny

    Nice work.

    Tony
     
  5. Mar 3, 2019 #5

    RKeller

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    weight as shown, RPSMA but no antenna is 13.1 grams. Weight with wire antenna would be 12.5g. openlog with card and header adds 2.3g to that.
    I was thinking about laying out a pcb without the charger, logger and switch. that would cut 20mm off the length and you could fit another 50-80 mah on the battery if you wanted. Would probably only cut a 1.5-2 grams though. you'd be removing a chunk the same size as the openlog for reference.
     
  6. Mar 3, 2019 #6

    RKeller

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    my co-workers and friends started calling me the red squirrel. I kinda went with the name, even made a little logo for my projects. although it's blurry in the pic. nut finder was just a good fit lol.
     
  7. Mar 5, 2019 #7

    RKeller

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    Added a connector for the battery, a stubby antenna, and installed the openlog unit. Then tried out the clear shrink tube. looks pretty good, the led's are super bright through it, even at only 1mA. I used an xacto to cut out the USB port.
    [​IMG]
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    [​IMG]
     
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  8. Mar 19, 2019 #8

    midpower_madness

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    Awesome!
     
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  9. Apr 1, 2019 #9

    PhysicsGuy

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    Very nice work. Would you mind sharing what GPS module you used? I've looked as close as I can at your photos, but I didn't recognize the module that's on your board.

    Thanks.
    --MARK
    NAR 65148, L1
     
  10. Apr 1, 2019 #10

    RKeller

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    Thanks Mark! The module is a Quectel L96.
     
  11. Apr 2, 2019 #11

    PhysicsGuy

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    Thanks Riley, I am only vaguely familiar with the Quectel stuff. If I'm correct, they make a lot of modules for portable devices. I don't normally see any of their products at the places I usually shop for electronics.

    Again, I'm impressed with the small size you have achieved.

    --MARK
     
  12. Apr 2, 2019 #12

    RKeller

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    Thanks Mark, one neat thing about this module is how much you can change the configuration. For example by default it is limited to 10,000 meter altitude, but it can be set to balloon mode which is good to 80,000 meters!

    While I wait for rocket season to start I've been working on a receiver. It has some neat features in it, but it's definitely pushing my programming skills (or lack of) up a notch.
     
  13. May 1, 2019 #13

    RKeller

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    I made another thing, this one is smaller than the other thing...
    16mm x 31mm plus wires. As shown with wires it's 1/4 ounce. I tried some new stuff for programming the frequency and so far it's working great. This just has one micro connector that you can just plug in and program. No switches or jumpers needed.
    [​IMG]
    [​IMG]
    [​IMG]
     
  14. May 1, 2019 #14

    SpaceManMat

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    Wow, are your ungoing to start selling these as a kit?
     
  15. May 1, 2019 #15

    RKeller

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    Probably not very good as a full kit. The gps module surface mount pads are all underneath and other components are pretty tiny. I reflow soldered the top then hand soldered the transceiver module and wires on.
     
  16. May 1, 2019 #16

    cwbullet

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    Maybe not a kit but there is a market for them.
     
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  17. May 2, 2019 #17

    RKeller

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    well, first I need a chance to fly them. Our weather has been crap. Apr launch was cancelled, hopefully May is better. In the mean time I keep testing what I can and tweaking designs.
     
  18. Jul 23, 2019 #18

    Leo Deelman

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    FYI, we tested the Quectel L96 using a HackRF SDR and GPS-SDR-SIM software. The L96 recorded speeds up to 3200km/h with a max altitude of 120km. A reference measurement on a Ublox Neo 7m, resulted in a max speed of 1800km/h and 50km altitude, which is in good agreement with data from real launches.
     
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  19. Sep 9, 2019 #19

    samtc

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    Any update the testing?
     

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