Long range serial communication device

Discussion in 'Wireless & RF Design' started by Rareş Iova, Mar 14, 2018.

  1. Rareş Iova

    Thread Starter New Member

    Mar 14, 2018
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    I want to build a high load drone that I would wish to be easy to expand. I plan to use a raspberry to feed the flight controller commands and do various calculations.

    My problem is that I would like to have it directly connected to a laptop on ground, preferably using serial and I have no ideea if there are any devices that would allow long range serial communication.

    GSM would be out of the question because of the latency. Basicaly what I'm looking for is something similar to an usual 2.4Ghz transmitter/receiver, but 2-way and if possible, by serial in order to connect it to the laptop and raspberry.

    On the drone I have a main battery with 4 cells and 16000 mAh and a BEC that is able to provide 5V, if the device would need external power.

    Any suggestion?
     
  2. Ian Rogers

    Well-Known Member

    Dec 12, 2012
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    How far.... Bluetooth can go quite a distance... up to 150 meters!

    Most rf devices sub 1Ghz and 2.4ghz can get 250 meters.
     
  3. Rareş Iova

    Thread Starter New Member

    Mar 14, 2018
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    I'm looking for something way more powerful. A range of about a km would be needed. This is why I expect an external power source to be needed.
     
  4. Ian Rogers

    Well-Known Member

    Dec 12, 2012
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  5. Rareş Iova

    Thread Starter New Member

    Mar 14, 2018
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    Seems promising, however I'm not entirely sure it is end to end communication as It seems it would require a gateway? I might be wrong?
    I've found one of those LoRa devices for quite cheap here: https://www.microchip.com/DevelopmentTools/ProductDetails.aspx?PartNO=DM164138 However I would still need said gateway.
     
  6. Ian Rogers

    Well-Known Member

    Dec 12, 2012
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    When I tested them they didn't need a gateway... It just transmits 256 bytes.. I needed a really low power solution.

    You can set these up as virtual cable...

    Here is the raw parts datasheet.. Where in the world are you as I have two I'm never going to use..
    https://docs-emea.rs-online.com/webdocs/1536/0900766b815369be.pdf
     
  7. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    What is a gateway in this context?
     
  8. be80be

    AAC Fanatic!

    Jul 5, 2008
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    Just one thing to think about there are laws now about drones if it's over a limit you can get into trouble fast with one.
    Don't be flying this thing close to nothing.
     
  9. Rareş Iova

    Thread Starter New Member

    Mar 14, 2018
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    If you're interested to sell them, let me know.

    As I understood, the gateway is a way to have the LoRas connected to the internet for seamless connection.

    I'm aware of the drone laws in my region and I only plan to fly it on private property. Thanks for the heads up tho.
     
  10. Ian Rogers

    Well-Known Member

    Dec 12, 2012
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    Since I said that!! I have looked high and low... They are in my "Safe place" somewhere..

    When I find them( soon I hope ) I'll let you know.... They were only £11 each...
     
  11. Rareş Iova

    Thread Starter New Member

    Mar 14, 2018
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    That sounds great. Worst case I would really appreciate a link to where you got them from as it might be easier than search for them.
     
  12. Ian Rogers

    Well-Known Member

    Dec 12, 2012
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    I buy them direct from RFSoultions https://www.rfsolutions.co.uk/

    But like I said... Consumes too much power for me

    BTW... I found one of them!! Just one more to find..
     
    cmartinez likes this.
  13. sghioto

    Well-Known Member

    Dec 31, 2017
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    I don't know what the regulations are on drones in your country but usually when flying a drone it must always be in sight. 1 kilometer seems pretty far. Just a heads up as be80be mentioned in post #8
    SG
     
  14. R.E.

    Member

    Jul 29, 2017
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    5 volt, 3km range for reliable 1km data link, not too huge. You need two.
    Take your chances on this.
     
  15. Randy S

    New Member

    Jun 19, 2017
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    Rareş Iova,

    Getting Started with LoRa / Build a LoRa Radio Link

     
  16. Plamen

    Member

    Mar 29, 2015
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    The oldest classical telegraph comes to mind. It operated over huge distances at a modest rate of 50 Baud by using current reversal. Zero or One is represented by one or the other polarity of the current (say 20 mA). The line driver could be self made by two current sources (simplest junction FETs say from + side) with two opposing switches (BJT or MOSFET say from GND) forming a bridge. The two switches are controlled in complementary way. The line is driven in differential manner. One switch grounds one end, the other is driven by the diagonal current source.
    The transmission follows START/STOP principle (start bit, number of data bits, stop bit...like RS232. I have used this over 1.2 km distance, but the history of telegraphy promises more.
     
  17. R.E.

    Member

    Jul 29, 2017
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    16
    So you are proposing attaching kilometers of wire to the drone? Probably not a good idea.
     
  18. Plamen

    Member

    Mar 29, 2015
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    The communication in question is between a RP and a laptop. RP in turn is controlling the drone, supposedly using the RC coming with the drone. The proposed telegraph style communication makes sense only If the the laptop is indeed km away from the RP and there is an existing twisted pair over the distance.
     
  19. Janis59

    Active Member

    Aug 21, 2017
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    Unbeatable for distance is LORA. The tiny pcb printed omni antenna gives at least 1/2 km over land, it means 3/4 km in air, the lambda/4 stick will give nearer to 3 km, but if some kind of not much element Yagi, - who knows, the hope is rather near to 10 km. Exists a modules allowing to communicate with USB port, however we are producing it for our needs ourself including there ARM core. Or use a Hack-RF1 but I am not sure there exists a ready drivers for LORA. Search it before buy. Third option is to use a LORA genuine capability to speak in RS232 terms, thus buy China dongle RS232-to-USB in ebay for 98 cents including postage.
     
  20. Janis59

    Active Member

    Aug 21, 2017
    651
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    RE""You have to send large chunks of data in one burst... It was designed to send complete web pages.."" No no, sir! :) We are using to send in one burst 5 parameters each 8 bits, what is demanding a microseconds. Then sleep. Everything works well in thousands of devices; many years 24/7. It has name a "telegrams".
     
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