camera drone build

Discussion in 'General Discussion' started by miky94, Feb 8, 2019.

  1. miky94

    miky94 Well-Known Member

    Hi,
    I'd like to build a quad with these qualities:
    - easy to fly
    - easy to carry
    - long flight time
    - able to carry a camera
    - reliable

    now I have a 330mm quad and it would be nice to recycle some component, I have:
    - 4500mAh 3S LiPo
    - Matek F405 FC
    - 30A 2-4S ESCs
    - 2212 920kv 3S motors
    - 8045 props
    I'd like to 3d print a light and resistant folding frame, but maybe to increase flight time I should go on something bigger, because I don't think I could mount props larger than 8", perhaps 9", not 3 blades because I would have more vibrations right? maybe a 450mm is better for this purpose?
    I'd use a 4S LiPo but I was wondering if a 6S would make sense, even if ESCs and motors are expensive. is there a rule to choose the right balance between capacity and weight?
    going larger which motors do you advise?

    Thanks
     
  2. wafflejock

    wafflejock Well-Known Member

    Hi no direct answers or experience with larger craft so can take anything I say here with a grain of salt:

    https://innov8tivedesigns.com/images/specs/Prop-Chart-Instructions-B.pdf

    ^^ write up here does a great job I think detailing how to work out efficiency for given set of motors/props but doesn't get too much into battery selection itself.

    Regarding the battery I have a lot of experience working with LiPos and discussing with others on the esk8 forum and here so can explain some of that and run some numbers to see if I can figure out if there is some best number to go with for a given set of requirements.

    When talking the capacity of the battery you should really look at it in terms of Watt Hours (how many Watts can it deliver for how much time, 1 Watt for 1 Hour is 1 Wh). The number of cells in series or 4S vs 6S is telling you the voltage but without accounting for the mAh you don't know the actual capacity or Wh, if you have say a 1.5Ah battery (1500mAh) and it is 4S (3.7V nominal/average voltage) then you have 4 * 3.7 * 1.5 = 22.2Wh, if you have same number of cells but 2Ah battery it's 4 * 3.7 * 2 = 29.6Wh. Generally for esk8 application we aim to use around 8S - 12S batteries because at higher voltage we can get more watts without increasing the amps too much and it's basically the limit of the components on the ESC (60V hard cap on the MOSFETs I think, maybe MOSFET driver chip DRV8301/8302 is limiting as well), more amps is more energy lost as heat so generally speaking higher voltage is more electrically efficient. That said for quadcopters, based on the PDF linked above running the props at higher speed means more energy lost to drag on the edge of the prop instead of going into lift so lower rotor speed I guess is ideal to minimize losses.... anyhow yah some preliminary thoughts will let you know once I have a chance to do some calculating but curious to hear others with actual experience on larger craft chime in as well.
     
  3. LoneRCRanger

    LoneRCRanger Well-Known Member

    Ok,, you lost me with the word "When..." If I was an Engineer, I'd probably be driving Diesel Locomotives.
     
    mark jackson and wafflejock like this.
  4. miky94

    miky94 Well-Known Member

    if I understand, higher voltage is more electrically efficient but it means more RPMs then less props efficiency and more energy lost as heat, so what is better, high or low voltage?
    I guess the answer is high voltage, that means more power, but using greater stator diameter and low KV motors which has more torque, mounting largest props, right?
    but more cells also means heavier battery and maybe I don't need so much power since I'm looking for efficiency and lightness.
    for the size of the build I'm thinking of probably 4S is the right choice, I have a 4500mah 30C 360g LiPo.
    that said, I would not complicate things starting from zero but I'd use a well tested and reliable combination of ESCs/motors/props.
     
    Last edited: Feb 8, 2019
    wafflejock likes this.
  5. wafflejock

    wafflejock Well-Known Member

    Yah I think you're pulling all the right information out of those random facts, a higher voltage is ideal a lower corresponding kv to keep the RPM at a reasonable level and having larger surface area for the prop is probably your best bet. I use ecalc.ch for doing calculations, but it is a bit cumbersome can get a rough idea without getting into all the component detail with this calc too https://www.omnicalculator.com/other/drone-flight-time from what they describe in the summary there a 10S battery with 8.8Ah will get about 30min flight time (using a lot of assumptions that boil down to it taking 170W to lift each kg on the craft). Adding extra cells in series or larger capacity cells does increase weight and at some point that weight is going to more than the thrust the motors can produce so you'll no longer be able to hover but where is the best combo for flight time still isn't really clear to me...
     
  6. miky94

    miky94 Well-Known Member

    However I compared LiPos at the same capacity of my battery brand:
    cells g/Wh
    3 5.597
    4 5.390
    6 5.309
    and 6S seems to have a better g/Wh ratio
    also for long flight time I've seen many build using Li-Ion batteries, what do you think about it?
    for the motors if I understood I should look for highest stator width and lowest stator height right?
    about props I know that larger is better but since I'm limited by frame size maybe increase the pitch would be an option?
     
  7. RENOV8R

    RENOV8R Well-Known Member

    ecalc is a great tool for checking the compatibility of your components and setup. I always check this when building larger quads
    https://ecalc.ch/
     
  8. miky94

    miky94 Well-Known Member

    yes I know it , unfortunately few components are free available.

    anyway comparing LiPos at the same brand and capacity I've seen that increasing the cells the g/Wh efficiency increases.

    watching painless360 endurance quad build series he didn't use a 4S even if it was more efficient in hovering and more powerful at 100% throttle. he tested it on an EMAX RSII 2306 1600KV which is 6S capable but specs say that it is for 5" or 5.5" props. so the reason is that using larger props it is too stressed?

    in the following serie he ended up using DJI 2212 920KV E300 which were made for larger props.

    mine are only 3S capable so I'd like to try this kind of motors on 4S or more , do you know some motor with thos specs? if possible not expensive...
    I'm looking for the simplest way to connect PDB/FC/ESCs, I don't know if I should buy the PDB FCHUB-6S for the Matek F405, I've also seen 4 in 1 ESC boards. what do you think about that?
     
  9. RENOV8R

    RENOV8R Well-Known Member

    Too many variables, too many questions. Especially when you haven't determined what frame you are going to be using. And that's the basis of any build, match the components to the type and weight of the frame. But to answer your ESC question, I use single ESCs on most of my builds, easier and cheaper to replace I than all 4. Here's a 300mm medium/long range build I'm in the middle of using single ESCs:
    022.JPG
     
  10. miky94

    miky94 Well-Known Member

    I'd use 10" props trying to build a 3D printed minimalist frame, wide stator and low KV motors, 4 in 1 ESCs, Matek F405, if it makes sense 4S or more
     
  11. RENOV8R

    RENOV8R Well-Known Member

    I wouldn't suggest a 3D printed frame for this size build. PLA or PETG is much too brittle and if you go with something more exotic like TPU or nylon, the frame will be too flexible and you'll never get a proper tune. This is from experience not just opinion
     
  12. miky94

    miky94 Well-Known Member

    I'd use aluminium for arms or something like carbon fiber, and plastic only for junction parts, but I still have to do the maths to find out if it's worth it
     
    Last edited: Feb 11, 2019
  13. RENOV8R

    RENOV8R Well-Known Member

  14. miky94

    miky94 Well-Known Member

    yes maybe a bit heavy but the greater height isn't a disadvantage for the torque?
     
  15. miky94

    miky94 Well-Known Member

    @RENOV8R in your image I seem to see 4 separated ESCs.
    I decided to use a 4S2P Li-Ion, 60A of continuous discharge current should be ok.
    I don't know if to buy the Matek FCHUB-6S PCB or a 4 in 1 ESCs board, what do you advice?
    Do you also know some wide and low kv (<1000) motor not expensive?
     
  16. RENOV8R

    RENOV8R Well-Known Member

  17. miky94

    miky94 Well-Known Member

    I'd opt for a 4 in 1, do you know any that can act as PDB with BEC for FC and other?
    maybe a bit big motor, weights 100g and pull 15" props, it draws to much corrent for Li-Ion but perhaps using 10" the drawing decreases.
    I'm following this build but I want to use a 4S, I'll try my unbranded 2212 920kv which are 3S rated, and if they will burn I'll look for something else
     
  18. wafflejock

    wafflejock Well-Known Member

    Just saying "LiIon" or "LiPo" is almost meaningless by itself would need to see what cells, if you are talking about 18650 cells and typical discharge rates then it's somewhere between 5-20A depending on the particular cell just 2P in parallel probably isn't "enough" or rather you may run up against the limit on the batteries and reduce their life (also run out of current for giving the motors extra torque, the magnetic field is directly related to the current, also also if the voltage dips too much under load then you could lose video or other control as well and definitely wouldn't be getting max RPM which also means some sacrifice in agility)

    http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/curloo.html
     
  19. miky94

    miky94 Well-Known Member

  20. wafflejock

    wafflejock Well-Known Member

    https://www.amazon.com/INR18650-30Q-3000mah-Li-ion-Battery-Samsung/dp/B014QNI1HK
    http://dalincom.ru/datasheet/SAMSUNG INR18650-25R.pdf

    ^^ these are the two cells I usually see people talking about on the esk8 forum but usually there we're looking at 10S4P or 10S5P to keep the discharge rate high enough to not be stressing the batteries (different application so different power requirements but just saying we usually only pull 3-4A while cruising but during initial acceleration can be 20A or for bigger guys going up hill 40A or more). It's a trade off in longevity of the cells vs flight time for a single flight and overall stability. The more overhead you have in the max discharge vs what you actually pull the better off everything will be.

    Can see a chart here from my esk8 with the amperage and voltage (can see as amperage increases red lines go up and voltage the blue line dips down then recovers) https://metr.at/r/GLCvO pretty sure this data is after I changed to using Turnigy 10S 20-30C discharge lipos (2 x 5S 5Ah packs). Also this was a relatively relaxed ride have seen some of my own with 20A max discharge when I'm punching it out, basically if you aren't doing anything too crazy with it then you won't need to throttle up so hard but if you do throttle up hard you run the risk of not having enough power and therefore things getting wobbly (or maybe worse but probably just wobbly would be my guess)
     

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