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How does a GPS receiver/transmitter (transceiver) work on a circuit board?

Discussion in 'General Electronics Discussion' started by MadeleineRS, Jan 6, 2017.

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  1. MadeleineRS

    MadeleineRS

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    Jan 6, 2017
    I'm working on a project at the University of Portsmouth and need some help with the electronics side of things.

    The attached photo shows how (I want) this project to work but I need to know details on what components are needed for the circuit board to allow this to happen.

    Looking at bullet point 9 and below in the attached image how will the device be able to transmit location data as well as receive signals which are sent out?

    I have done research on GPS and aGPS (Assisted-GPS) signals and have found a HSGPS receiver chip which I assume receives signals which are sent out? (HSGPS chip: http://www.furuno.com/en/products/gnss-chip/ePV5800B[MS1])

    Would this chip be connected to the circuit board? What else is needed for this to be feasible?

    It also needs to fit within the size of a Ski Pole handle grip, so the components needs to be reduced into a compact circuit board.

    What I have concluded from a small section of research is:

    Having looked into how GPS and Assisted GPS work it looks like using assisted GPS in the device would be more accurate as it uses mobile phone towers as well as ‘Trilateration’ to determine users location. If this is the case, I believe this means the device will need a SIM CARD card which connects to mobile networks in the users location as well as a GPS chip connected to the internal circuit board.

    Is this correct? If so how would all of these components fit together?

    Thanks.
     

    Attached Files:

  2. garublador

    garublador

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    This is a fairly big project that a design firm would probably have a few engineers assigned to it. So from us you'll probably only get some general information.

    At a very high level it sounds to me like you'll need to pick some sort of processor that can interface easily with the mobile phone module as well as the GPS module (interfacing with the GPS module looks easy, FWIW). You'll need to figure out what the "alarm" consists of. The "OK" button is probably easy to integrate electrically. Then find some way to power the whole thing. All that stuff would go on one or more circuit boards depending on the mechanical design. There will be a bunch of additional components, but you won't know exactly what until you have picked all the major components and looked at their datasheets and hopefully reference designs.

    My first thought is the electrical design is pretty straight forward, but the mechanical and software part of it could be tricky.
     
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  3. MadeleineRS

    MadeleineRS

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    Jan 6, 2017
    Hi! Thank you for the quick response!

    Just so you know, I don't actually have to manufacture this and make the circuit boards I just need to understand how it would work and what components would be needed to make this feasible.

    You mentioned a processor with the mobile phone mobile and GPS module, would the mobile phone module consist of a SIM Card like I mentioned in the original post? Would the modules and 'processor' be on a circuit board?

    All I need to know is what components are needed. I.e. Do I need the HSGPS chip I mentioned? Do I need a transmitter like components to be able to transmit data back? (if there is such a thing?).

    Thanks again!

    What I really need to understand is how the device will transmit data back to mountain rescue
     
  4. BobK

    BobK

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    there are 3 main components you would need.

    1. A GPS module. Note module, not chip.
    2. A GSM module. This is the cellular communication part. It would use a SIM card to connect with a carrier. A SIM card alone does not do anything except identify the subscriber.
    3. A microcontroller or microprocessor to glue it all together.

    And then there is the custom software to run it all.

    If you look at commercial products for tracking pets or children, you have essentially the same thing.

    Bob
     
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  5. garublador

    garublador

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    I don't know a whole lot about the modules used to communicate with a cell network. So I'm not sure if a SIM card is necessary or if you can buy modules with that functionality built in. There may be a possibility to find a CPU with that functionality built in.

    Based on the file you attached it sounds to me like the requirement is to have these devices on a cellular (mobile) network just like a mobile phone, so you'll need some sort of module that performs that function. That module will connect to a CPU in your device. The GPS module will also connect to the CPU in your device. All those components will be on printed circuit board(s).

    You'll need something to communicate with the cellular network, something to find your location (that chip you gave is an option), something to control it all. I'm imagining it as three devices (with companion components), but there may be some highly integrated components that have one or more of those logical parts built into one physical component. They'll all be on circuit boards and communicate with one another on that board(s).

    This is ignoring the alert, "OK" button and power.

    It sounds like they'll literally be texting the information back and forth on a cellular network. So your device is more or less a mobile phone with a bunch of functionality stripped out (no screen, no microphone, etc.)

    The block diagram in the original post is very close to what I'm describing. I'd change the "Ski Stick Interface Circuit" into two blocks, one called "CPU" that's in the same place as the "Ski Stick Interface" block and another called "GPS" that has arrows pointed to both it and the "CPU" block.
     
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  6. hevans1944

    hevans1944 Hop - AC8NS

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    Everything you need is already integrated into a smartphone. All you need to do is write an app for the phone, then duct tape (or otherwise attach) the phone to the ski pole handle. Problems I see with this approach are (1) limited or no range with cellphone buried in snow; (2) limited battery life and power availability in colder temperatures; (3) lack of GPS satellite "visibility" when cellphone is buried in snow.

    If a skier is overcome by a snow avalanche and is buried under several feet of snow, it may seem reasonable to expect that a device mounted on (or in) a ski pole handle would have a better chance of establishing two-way communications with a rescue HQ cell phone, and also be able to receive GPS satellite signals IF the ski pole can be poked above the snow pack to allow reception and transmission of gigahertz band signals. However, there exist Personal Locator Beacons or PLBs, some with GPS, that are sold specifically to alert rescue teams and help locate people in trouble. The frequencies used are around 406 MHz rather than gigahertz, so propagate better (except for the GPS functionality) and are able to be continuously monitored by satellites. Perhaps you should look into how those work, and the International distress call frequencies they use, before re-inventing this particular wheel.
     
    MadeleineRS likes this.
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Yeah, what Hop said.

    If you try to find the location of the ski pole after it's under 10 feet of snow and ice, you're not going to have a lot of success.

    Far better to periodically track the location of the ski pole. Then if it stops responding you know approximately where it was. If you're lucky enough to still be in contact with it, even better (you can get a fix).
     
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  8. MadeleineRS

    MadeleineRS

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    Jan 6, 2017
    Thank you so much for your help! It's been very useful.

    I've been trying to draw this up but did you mean arrows pointing from the mobile phone receiver/transmitter to both GPS module and CPU?

    If wanted to add a small speaker which emits a high pitched sound when the signal from mountain rescue reaches the device, how would that fit into the block diagram?

    http://117.18.68.88/en/page/app_guide_mobile_phone.html

    The link above shows a mobile phone block diagram, would I need a processor connected to the CPU and an 'Audio Codak' as seen in the diagram? What other components from the mobile phone block diagram would I need?

    If you have time I'd really appreciate a a rough block diagram drawn out for me so I can understand what you meant by the original comment.

    Thanks again!
     
  9. garublador

    garublador

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    Electronics for Ski Pole 1.jpg

    Here's a quick modification I did to the block diagram you had. I just replaced the alert block with "Audio Codec" to be a bit more specific. I'm not sure you'd need the "base band processor" like in that link, but it might depend on the CPU you pick.
     
    MadeleineRS likes this.
  10. BobK

    BobK

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    Nice,garublador!

    An audio codec is probably not required. The cpu can make an alarm sound easily.

    Bob
     
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  11. MadeleineRS

    MadeleineRS

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    Jan 6, 2017
    Ahh thank you for this! That's a lot of help!

    Is the block that states 'Mobile phone transceiver/receiver' the GSM module? Can I rename it to that?

    Also if you can help me with one more issue. Can a lithium ion battery, like in a phone fit to this circuit board? And how small can they be whilst still having the same power as a mobile phone?
     
  12. MadeleineRS

    MadeleineRS

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    Jan 6, 2017
    If a audio codec is not needed, how can the CPU make an alarm sound?

    Thank you!
     
  13. garublador

    garublador

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    That would make sense, but I'm not sure you need my permission. ;)

    The form factor used in current mobile phones might not be all that well suited to fit in a ski pole, but yes it would work. Here's a typical sized phone battery:

    https://www.amazon.com/Samsung-Replacement-Warranty-Discontinued-Manufacturer/dp/B00BW0X892

    (0.8 x 3.5 x 7 inches)

    The "18650" type lithium ion batteries might work better because of the cylindrical shape.

    https://www.google.com/#q=18650
     
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  14. BobK

    BobK

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    A cpu can pretty much make any sound you want digitally by simply manipulating an output pin. A simple square wave (i.e. on off repeat) is suitable for an alarm sound and is trivial to make. A codec is used for compressed audio streams, which is quite a different thing.

    Also if it is just a simple alarm sound that is needed, a piezo buzzer will do that. If you need more, a few components (low pass filter, and audio amp) would be needed on the board. I would probably go with a piezo buzzer, which will be no larger than the speaker you would need for full audio.

    Bob
     
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  15. MadeleineRS

    MadeleineRS

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    Jan 6, 2017
    Thank you so much for this! very useful, and sorry for so many questions, how electronics work is a new subject to me!

    Do the cylindrical batteries hold the same power/stay charged for at least a day like a phone does? I'm assuming it could last longer as it does not have to power a screen or other mobile phone components?

    Update: Having looked at the batteries you suggested, how would this work with a micro-USB charger or would I need a different type of battery for that?

    Ideally I'd like the device to have a micro-USB port with a rechargeable battery inside.

    Do you know how this would fit into the circuit board?

    Sorry for so many questions!
     
    Last edited: Jan 11, 2017
  16. MadeleineRS

    MadeleineRS

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    Jan 6, 2017
    Thanks Bob, this really helps.

    All I would need is a high pitch sound that's emitted when a signal reaches the device. So in the block diagram above, instead of Audio Codec, do I just put Piezo buzzer?

    And also, for the buzzer to emit sounds, would the CPU have to be programmed? And if so what programs do you use to do this? (Obviously I won't be actually creating this device but I need to know how it would work).

    Thanks again!
     
    Last edited: Jan 11, 2017
  17. garublador

    garublador

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    The 18650 has a relatively large capacity compared to a phone battery, but it's also physically larger. It's just a common type that's in a shape that lends itself better to your form factor.

    Your guess that it will last longer than a normal phone because of the reduced functionality is probably correct. You'll want to be careful to make sure you can get most of your components to "sleep" (go into a low power state) when they aren't being used. I suspect you could get a day out of it with a battery like that pretty easily, but I'm not familiar with how power hungry the GSM modules are.

    As for the CPU, there may be specialty SoC's (systems on a chip) that would work that have build in RAM and storage, but that would have to be accounted for in the "CPU" block. It may require separate RAM and some sort of storage (eMMC perhaps). How you actually get your code on the storage device will depend on the CPU you pick. It may be programmed from a PC through a USB port or through some other type of programming connector on your PCB.
     
  18. MadeleineRS

    MadeleineRS

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    Jan 6, 2017
    Thanks again, just what I needed!

    You replied to my comment after I made an edit to it so I'm not sure whether you saw my other questions.

    Update: Having looked at the batteries you suggested, how would this work with a micro-USB charger or would I need a different type of battery for that?

    Ideally I'd like the device to have a micro-USB port with a rechargeable battery inside.

    Do you know how this would fit into the circuit board?

    Again sorry for so many questions!
     
  19. garublador

    garublador

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    Oct 14, 2014
    You can use that battery, it's just that you'll need charging circuity. It's part of the "Battery Management/Charging" block in your diagram.
     
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  20. BobK

    BobK

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    Jan 5, 2010
    Yes, if all you want is a high pitched sound, the piezo buzzer is ideal. They can be very small and loud and efficient,

    How you program the cpu depends on what type you use. For this app, I would think microcontroller would be sufficient and they are very low cost, low power. Cell phones use a more sophisticated microprocessor, but that is because they do so much more than you need.

    Microcontrollers are typically programmed by a programmer that connects to a PC via USB.

    Bob
     
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