New Flight Computer - would you be interested?

Discussion in 'Rocketry Electronics and Software' started by Stomper, Sep 21, 2018.

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  1. Sep 21, 2018 #1

    Stomper

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    Hi Guys,


    I am an electronics engineer and I am planning to build a professional flight computer for model rocket enthusiasts.

    These are my main goals and the main features I want to build in.

    • LiPo Battery powered with built in micro-USB charger (~3-4 h runtime)
    • 3 general purpose I/Os for future add-on or own electronics or maybe trigger inputs etc.
    • Global positioning with GPS
    • 3 axis accelerometer
    • 3 axis gyroscope
    • 3 axis compass
    • Air pressure measurement to determine height (+/- 1 meter exact)
    • Temperature measurement
    • Log all data on removable SD card (raw data and calculated data)
    • Live telemetry data over 868/900 MHz data channel (~30 kbps) (~1000 m los)
    • Two power outputs to fire on user events (altitude, time etc.) for chute ejection load or something.
    • Loud buzzer for easy recovery
    • < 75 g electronic and battery together


    Main goals are
    • determine and record the exact flight path to show on google earth
    • gather as much as possible data and log it on SD card
    • Telemetry for live data and GPS position for recovery
    • Easy to configure over config file on SD card
    • Live landing position prediction for easy recovery
    • Remote fire/launch of rocket and/or remote control of equipment.

    Complementary Product is a telemetry receiver to connect to your laptop for live data.


    The first question is… is someone interested in such product and how much are you willing to pay for it?
    Is there something similar on the market?

    I am building it from scratch but I have not very much experience in model rocket flights.
    So I want to ask the experts for functions you would like to have and/or witch are useful.

    Best regards
    Stomper
     
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  2. Sep 21, 2018 #2

    timbucktoo

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    Sounds cool. I would prefer live telemetry to smart phone instead of laptop since I never bring laptop to launches. The first product that comes to mind that pretty much does that is the TeleMetrum. Base price without ground station is $300.
    https://altusmetrum.org/TeleMetrum/
     
  3. Sep 21, 2018 #3

    BrAdam

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    Skip the SD card and log to the device. Download or telemetry to smart phone like timbucktoo said. 3rd pyro channel for staging purposes.
     
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  4. Sep 21, 2018 #4

    les

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    I would shoot for 4 output channels like from Featherweight.
    Also you need to ensure you won't lose connection to the SD card (since it is removable) during launch with the vibration and G forces.

    I'm curious about the "live landing position". Here in the Northeast our launch areas have terrain (hills) so the landing area can vary significantly from the side of a hill vs flat terrain
     
  5. Sep 21, 2018 #5

    Jmhepworth

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    I would prefer the distance provided by the 70cm band rather than 900Mhz.
     
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  6. Sep 21, 2018 #6

    cwbullet

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    That being said, there is a much larger market for 900mhz.
     
  7. Sep 21, 2018 #7

    Eric

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    I agree 900 mhz, and at least 3 event channels. The Eggtimer TRS does my altimeter and GPS all in one. But its a pretty good size foot print. Out the door kit for everything you need is about $190.

    Might pay $250 ish for a smaller unit with 3rd channel. Much more and I would be content with current market offerings.
     
  8. Sep 21, 2018 #8

    Earache

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    Take a look at the AIM XTRA. It has most of the features you listed along with real-time announcement of altitude.
     
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  9. Sep 21, 2018 #9

    SteveThatcher

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    sounds interesting, but I would suggest you look at the marketplace in rocketry more. As other people suggested, look at AltusMetrum, EggTimer, Featherweight, and MARSA. You are outlining what would end up being a high end device and expensive. The cost for me would already rule it out (but I am basically cheap...).

    personally, I would skip the battery charger. I would rather swap out a battery than connect up a charger to a rocket. People may want a separate battery for pyro rather that just sticking with one also.

    Multiple outputs are great and can be used for other things like camera control and staging. They just need to be easy to setup and versatile.

    I would skip the SD card also. There are plenty of high density non-volatile memory ICs that can be connected up by SPI or I2C (that take less real estate on a board). The fewer the contacts in the device, the less chance for a failure.

    Speaking of setting the device up, if you have a transceiver on it for telemetry, then that is your method to connect up to it and make sure you have a 3 pin serial I/O running at 9600 baud on it (good for testing anyway). I am not a fan of doing things through a cell phone (personal taste). You can put a rudimentary web server on the device and access things through any platform as long as you have a USB transceiver dongle for the radio. I guess I am also suggesting don't do a bunch of proprietary protocols, etc.
     
  10. Sep 21, 2018 #10

    boatgeek

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    Onboard battery might be OK, but I'd be perfectly happy with an outside battery. Three or four pyro channels would be nice. A switch terminal (see Stratologger CF for example) is really nice. Bonus points for switching the GPS separately from the pyro channels so that you can start up the GPS during assembly and not arm the electronics until you are at the pad. Or maybe have the whole unit power up into a GPS only mode until the switch is closed at the pad.

    And can you fit all of that into a 24mm tube at a price point of $50? :)
     
  11. Sep 22, 2018 #11

    cbrarick

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    be able to inhibit a channel if there is a user defined amount off vertical
     
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  12. Sep 22, 2018 #12

    OverTheTop

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    Some extra channels that can be used to measure and record analogy voltages with the other flight data. The TeleMega I use has a total of six pyro channels, but I only use two for deployment. The other four can be fed analog voltages from other sensors and systems for recording. I use this for logging servo positions when flying my VTS and for monitoring the other altimeter batteries during other flights. I could use more than the four spare if they were available.
     
  13. Sep 22, 2018 #13

    Andrew_ASC

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    Plug and play system. Live Telemetry. Onboard storage. 440MHz. Do a kiddie version of 900 MHz for the crowd funding. 440MHz hands down More data transmitted father for money better antenna support Arrow yagis etc but more money for a flagship product line that reeks of quality. Easy to configure. Good user manuals showing users how to configure and use devices biggest problem on manufactures now. Selectable baud rates to from 2400 to 38400 or higher for 440MHz units. A Telemini V3 sized GPS tracker I’d give up the two pyro channels if somebody would make a GPS that small to fit into 18mm tubes with batteries. Lipo batteries 3.7V jst connector. Spark fun.

    And if they could make a Featherweight or TeleGPS sized gps with backup RDF and two pyro channels they would steal the minimum diameter market of 440MHz stuff. Sub $220 for tracker. Sub $150 base. Use higher quality sub components not cheat out 36 cent chipset. We want our freaking rockets back through trees and real obstacles like cornfields or tall grass near lakes. And sometimes not even line of sight. Flexible base system to larger boards like Aim Xtra or Telemega. My opinion.

    Laptop or IPhone/Android options.
     
  14. Sep 22, 2018 #14

    Andrew_ASC

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    Don’t forget AIM and Altus Metrum have open sources certain components and coding so if your device works with their 440 MHz bases and code well you earn more customers of the 440MHz crowd easier. Us 440 MHz users are picky for quality units. There’s plenty of 900 MHz unit competition of solder it yourself kits. Those guys may out price you lower.
     
  15. Sep 22, 2018 #15

    Andrew_ASC

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    In rocketry you have small 24,29,38 mm airframe minimum diameter rockets that fly several miles high, fast well over Mach 1 and 2, and far drifting usually with electronic deploy sometimes even dual deploy. Multistage rockets need tilt protections for pyro events. At this point the rockets are out flying the motor certified delays in seconds. You might need a twenty or thirty second motor delay but none exist. That is the push for pyro channels. Then you have larger 54mm and up rockets that fly faster, farther, and higher if minimum diameter. Or Lower and slower depending on how you build it and what motors. The 75 and 98mm and up crowds with L3 need massive amounts of data and channels. They don’t care how big unit is as much as how many features and redundancy. Just more ramblings. So in rocketry you find different gps and tracker sizes on 900 to 440 MHz markets for different rocket design needs. Some designs are more dimensionally critical like minimum diameters where you can go longer with a board but not wider.
     
  16. Sep 22, 2018 #16

    Andrew_ASC

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    My only gripe of AIM is they will not make smaller boards. Give me a GPS/RDF tracker 440MHz with less pyro channels as an option and a smaller footprint. Small enough to cram in a 24-29mm rocket. I had to go to Altus Metrum for Telemini V3 RDF and TeleGPS for small rocketry ham boards. They do not offer as many pyro channels. TeleGPS offers none and must be flown with a raven altimeter with tilt protection for example to have pyro channels on multistage 29mm rockets.
     
  17. Sep 23, 2018 #17

    Clivus

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    Some good ideas in this thread, but if you take them all it will look like The Homer
    [​IMG]
     
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  18. Sep 23, 2018 #18

    Andrew_ASC

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    One other oddball request. The reason I did not buy a 900 MHz Featherweight GPS is it had a integrated to board rubber duck antenna. Could you use a wire antenna that is flexible for the transceiver? I do not care if a ground station needs a duck or a yagi. A rubber duck limits the user ability to cram it into a tight nosecone compared to a flexible wire.

    My experience is limited to L-1 motors and some minimum diameter multistage designs. I just really prefer the 440 MHz hardware. I do understand the want for 900 MHz units as that eliminates the FCC tech license requirement. Other users of L-2 and L-3 motors may have very different design goals. Keep in mind even on L-1 motors some designs get 100G’s off the pad. Most crummy GPS will fail to maintain a lock over 60G’s. And the really bad units do not re-lock fast.
     
    Last edited: Sep 23, 2018
  19. Sep 23, 2018 #19

    watheyak

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    It has nothing to do with the GPS being "crummy". Please refrain from talking about things you don't know about.

    In a minimum diameter rocket with limited space I want anything but a wire antenna that needs to be kept straight. Ducky all day long...

    Besides, the antenna on the featherweight is not integrated, it's attached by an SMA connector.
     
  20. Sep 23, 2018 #20

    timbucktoo

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    In addition to the fact that Featherweight GPS antenna is connected by SMA, it’s only 2” and there’s more than enough room in 38mm NC.
     
  21. Sep 23, 2018 #21

    OverTheTop

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    Some GPS units are better than others, so time to reacquire can vary. The "better" ones will do it quicker but usually at the price of higher power consumption. You need to look at the "GPS" as a system. Antenna view, attenuation due to airframe and surrounds affect performance, including time to relock. Does it really matter? If it relocks before apogee and tracks to the ground then that is likely sufficient. If tracking it all the way through the flight is what you want you might define units that don't cope with this (or deliberately lock it out) as crummy. They are more than fit-for-purpose most of the time, just not in your particular application.

    As an engineer you will be required to design systems that need exceptional performance, or designs of lesser performance (and hence price), and some really mundane stuff, for different markets. Fit for purpose is your aim. The lower performance is not crummy, it is making money for the company you work for that pays your bills.

    Maybe a better choice of words was worthy of consideration. As others' have said, consdier prooof redding the post before you send :). If you have written something in anger, walk away from it for about an hour, then come back and proofread before you maybe send. That's what I do anyway.

    Horses for courses. I prefer wire personally (less mass). Whatever works is good, but I do prefer SMA or RP-SMA to give the option to change. YMMV.
     
  22. Sep 23, 2018 #22

    Andrew_ASC

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    The TeleGPS v1.6.8 handles a G load of 68G’s for university flight and tracked the entire flight during boost through landing etc. Telemetry has voice announcements. Tried it at 168G’s once for another university project and we ended up ordering a second unit. So all electronics have limits. GPS seem parculiarly sensitive to G loading and Mach numbers. I’m just a mechanical student. We recovered rockets through tree lines and over light 200ft terrain obstacles with 440MHz. Not certain a 900 MHz unit could do that over 1.8 km away. Treeline was dense. I’m sure the community would enjoy a lower priced 900 MHz variant.
     
  23. Sep 23, 2018 #23

    cerving

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    Some friendly advice from someone who's been there...

    Stomper, hopefully you fly rockets (preferably HPR) on a regular basis. That will give you a different perspective on what is needed vs. what you think might be needed by others. Designing a highly sophisticated FC with a lot of external input capability and telemetry is definitely a cool project, but look at the market... you're playing to the upper 2%, both in terms of capabilities that they want and how much they'll pay for it. If you're looking to make any money on this project (i.e. get your investment back), you may want to look at the other 98%.

    When I design something, it's almost always because it's something that I want myself and it fills a gap in the market. I do almost all of the flight testing myself, too... it's a good excuse to go out launching. You'll quickly find out that motors can be a major development expense, especially if you test with a full range from LPR to Level 2 VMax's, maybe with a L3 flight thrown in. If you farm out your beta testing to others, it's going to take a lot longer because now you're depending on somebody else's time schedule, and their rocket/motor choices may not be optimal for what you want to test.
     
  24. Sep 23, 2018 #24

    SparkyVTFlyer

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    Like FRAM? I'm new to all this and can't see avoiding SD cards. I use them in my flight computers because I record Mb's of data. A typical flight is about 15Mb of raw text. Even if I just stored the data as ints, longs, and floats, I'd still need at least a few Mb of storage. I can't find anything like that in FRAM. Is there something else that I've missed?

    BTW, I have a used at Teensy 3.5 SD card holder at 35Gs, oriented the worst possible way, and never lost contact. The Teensy3.5/3.6 doesn't even have the little SD retainer clip. In over 25 flights, I've never had the SD card vibrate loose.
     
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  25. Sep 23, 2018 #25

    OverTheTop

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    Have a look for eMMC (embedded multimedia card). It is basically an SD card but solderable. Managed file system etc...

    We use a MTFC16GAKAEJP-4M IT by Micron. Supported by UBOOT or Linux at least. I don't know which devices they might have in something a little more manageable than the BGA package :eek:
     
    Last edited: Sep 23, 2018
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  26. Sep 23, 2018 #26

    cerving

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    Personally, I think FRAM is a good buffering solution so you can spool out data as fast as you need to, while you wait for a good opportunity to write it to flash memory. If you do it right then you don't need all that much FRAM, which is a good thing because it's very expensive compared to other memory technologies.
     
  27. Sep 24, 2018 #27

    Stomper

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    Thanks a lot for all the great replies. There are a lot of useful input for me....

    I try to quote a few of the answers...

    Good Idea... what about a base-station witch receives the Sub-GHz Signal from the rocket and brings it to an BT connection, either on smartphone or laptop?


    You are right... with 100Gs the contacts might not stay in contact with the card... so I will use a built in memory.


    868 (Europe) and 900 MHz (US) uses new technology (LoRa) witch should reach distances up to 16.000 m LOS. Of course you need a very good antenna for that.


    I build a different device that needs a charger built in. So i get this as kind of waste from my other project... not much work to do here.
    battery will be removable via an JST connector.


    The plan is to provide a Windows-Software to configure and controll the electronic. For safety reasons the pyro channels are planned to stay disconnected (electronically) until you arm them by the windows software on your laptop (or smartphone).
    I try to layout the module as small as possible, lets see if 24 mm will be possible.... I dont thins so with all the functions. And 50 Bucks... mmm impossible :-D

    Good idea... I will design some Analog I/Os into it.

    Antenna will be connectable via U-FL or SMA connector... Not sure if the U-FL connector will withstand the 100Gs :-/

    Some general information...

    I am from Germany, so I will stick to the European ISM-Bands (868 MHz).
    The distance witch can be reached should be incredible with the new LoRa technology... some experiences here?
    Are the US/Australian people are allowed to use 868 MHz devices?

    I am building another device (confident) with nearly the same technology and functions. That s why a rocket computer is kind of waste from my other project. And it will definitely take some time to bring up the first prototype. But all the software will be made open source that you guys can recreate and edit everything you want.

    I come back here, if the first version is available and keep you up to date on the development process
     
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  28. Sep 24, 2018 #28

    Eric

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    What are you looking at for a current price point?
    And in the US, I dont think 868mhz is in our license free band
     
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  29. Sep 24, 2018 #29

    Andrew_ASC

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    900 MHz is license free over here.

    Otherwise ARRL says what we can use once licensed from the FCC. I hold a technician license. Exam fee $15 and good for ten years. Many companies offering amateur radio tech in US stick to 70cm with amateur technician licenses as customers. 70cm or 420-450MHz. There are some oddball 2m radios. Not certain about 868 MHz over here. May want to ask the FCC first or read up.

    http://www.arrl.org/frequency-allocations

    And

    https://www.fcc.gov/engineering-tec...es-division/general/radio-spectrum-allocation
     
    Last edited: Sep 24, 2018
  30. Sep 24, 2018 #30

    timbucktoo

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    Yes, AltusMetrum offers either a BT to smart phone/tablet or a Dongle to laptop, prices are $150 & $100, respectively. Again, these all operate on the 70cm Ham band.
    http://shop.gag.com/ground-stations.html
     

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