94 AMPS

Discussion in 'Cinestar 8' started by Nicholas Donnelly, Mar 17, 2015.

  1. Nicholas Donnelly

    Nicholas Donnelly New Member

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    Hello,
    Looking for anyone else that may be exceding 85-90amps with their cinestar?
    I can discuss my questions concerns directly but basically looking for experience on if the high current draw can damage the MK boards and if it's caused compass/magnet errors for anyone else.
    I'm flying a Cinestar8 HL w/ Movi M15, Epic-M brain, Canon 14mm L, and parralinx tomahawk.
    Cinestar is powered by 2x 10000mAh batts. Camera, gimbal, and DL all powered by 1x 6200mAh batt. In general, I'm seeing an average of 93-94 Amps.
    Thanks
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

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    Do you know what your "AUW" (all up weight) is? Getting a luggage scale or something to weigh the copter is helpful.

    But to answer your question, 85-90A isn't too high. Remember, that's going to 8 speed controllers and 8 motors, so that's 11-12A per motor. That's well within the stated operating limits of the MK hardware. And you're flying a relatively heavy camera package, so that might be just fine. The issue is whether you could encounter a situation where you'd be pulling significantly higher current. For example, high winds, or an evasive maneuver. And you should consider the possibility of losing a motor for any number of reasons, which will cause much higher current draw while the remaining motors try to compensate.

    IMHO, you're probably OK within a normal operating window, but there's a chance things could go badly if something untoward happens.
     
  3. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    The current draw is primarily going directly from the LiPo batteries to the Power Distribution Board and then out to the motors. The current does not flow through the MK Flight, Navigation, or GPS boards.

    The "normal" range of current draw you are seeing will vary depending on whether you are running 4S or 6S LiPo's. Which type are you using?

    Andy
     
  4. Dave King

    Dave King Well-Known Member

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    Is this at Hover?
     
  5. Nicholas A Donnelly

    Nicholas A Donnelly New Member

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    Thanks very much for the feedback. My AUW is exactly 28lbs. Seems like the only way to reduce the amperage would be to lose some weight, yeah?I'm using 2x 10000mAh 6S batts. The 94 amps is generally when moving slowly in any direction. At hover, I think it dips slightly to 89-91ish. Is it possible to review my mins/max in the flight data?
    Thanks again guys!
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    If you have the MK Navigation Control board and have installed a microSD card, then yes.
    Use a microSD/USB card reader and copy the .GPX files over to a PC and then download MK_GPXTOOL from http://wiki.mikrokopter.de/en/MKGPXTool -- it will allow you to see the mins/max in the flight data (and much more).

    Andy.
     
  7. Nicholas A Donnelly

    Nicholas A Donnelly New Member

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    Ok, so at hover, average current was around 89amps, w/ low around 81.7. At one point, while ascending, I actually spiked to 107.3 But again, average was around 91-94amps. GPX tool is great btw.

    The compounding reason for my concern w/ this is Im getting constant magnet/compass errors. I recently swapped out my m10 for an M15 and added a second battery to improve stabilization and flight time. The battery leads (& EC5 Y cable) are as far away from the navi as possible. However, I suspect that the high current draw is creating an EMF which is the culprit of my magnet errors.
     
  8. Steve Maller

    Steve Maller UAV Grief Counselor

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    Nicholas,
    You may want to invest in the MK External Compass. Ever since I got mine I have not had a single magnet error, and the numbers in my GPX files are very consisted WRT declination, etc. Installation is tricky if you have a Navi Ctrl 2.0 board, but simple if you have a 2.1 board.
    http://www.quadrocopter.com/External-Compass-for-Navi-Ctrl_p_1257.html
    Screen Shot 2015-03-18 at 9.13.31 AM.jpg
     
  9. Thijm le Grand

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    Don't know the prop/motor combi but 91-94A @12,7Kg/28lbs seems a bit high.

    Tested setups @ hoover and sea level
    60-64A Kw10v1 & 14x5 Xoar @ 11Kg
    70-74A Kw10v1 & 14x5 Xoar @ 12Kg
    76-80A Kde 4215 & 15x5 Tprop @ 13Kg
    88-92A Kde 4215 & 15x5 Tprop @ 14Kg

    Can you share your setup?
     
  10. Nicholas A Donnelly

    Nicholas A Donnelly New Member

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    Ah ha, didn't know that existed. I will check if it's compatible w/ MK GPS v.3

    Here's what I'm using for motors/props:
    image.jpg image.jpg image.jpg
     
  11. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    What's that fuzzy material around the GPS, Nicholas?

    Also, if you post an image of the central stack showing the LiPo wiring it might give a clue as to what's causing the compass errors.

    Andy.
     
  12. Steve Maller

    Steve Maller UAV Grief Counselor

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    Do you mean the external compass? It doesn't connect to the GPS, it connects to the Navigation board. It's compatible with the 2.0 and 2.1 board with the most recent firmware releases (not sure what version).
     
  13. Dave King

    Dave King Well-Known Member

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    Nicholas I would run 16 inch props if you have 550 booms. If you don't I would consider 550 booms with 16 inch props. That will probably jump you down about 3-4%. If going to 550 booms isn't an option I would consider jumping up to the Tiger 4120's. You have to be carefully when you are running the 4012's or 4014's as you can get to a certain weight and the copter just hits a break wall for headroom. You might be good enough right now but if you have a BL go out it might not be enough to safely land that EPIC safe.

    I would also remove the velcro from the GPS shield.
     
  14. Thijm le Grand

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    I think you are well above max efficiency on these motors.
    You could do a bench test with 16x5 as Dave suggested (check motor temperature). But lt looks like new motors is the best solution
     

    Attached Files:

  15. Nicholas A Donnelly

    Nicholas A Donnelly New Member

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    First, Copy that on the compass connection, thank you.
    Next, The Velcro is for a custom made weather cover that wraps around the bottom of the navi. This was invented after a single drop of water (snow actually) kicked up from launch pad and essentially shut down a full day of production... Does velcro cause problems for the navi?! Third is Damn!, I've already bought a complete spare set of each so I'm pretty invested in motors and props. That being said, I guess my new question is if I were to fix just one thing, what will have the most impact on performance as well as landing in the event of single motor failure? Is it the motors, props, booms (I have 500mm btw) or something else? Many thanks for everyone's feddback. It's greatly appreciated.
    Here are the photos of the wiring as well:
    image.jpg image.jpg
     
  16. Nicholas A Donnelly

    Nicholas A Donnelly New Member

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    Thanks Thijm, I posted before seeing your message and attachment. Sounds like the 4120's are the way to go.
     
  17. Thijm le Grand

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    I do not have any experiences with the 4120 motors. So maybe others can chime in.
    4120 ads about 100gr per motor. If you want to keep the 15inch props/ 500cm booms, 400kv might be to low when lifting more the 13kg.
     
  18. Dave King

    Dave King Well-Known Member

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    Nicholas do you have 550 booms? If you do I would suggest seeing where you are 16 inch props first. If you upgrade to 4120 motors you will need the new Quadrcopter motor plates and then open up the slots to accept 4mm screws. Just making sure you know what you are getting involved in. I know several guys running the EPIC with those motors. My question to you is are you sure on your weight? Last year with the copter, a very beefy gimbal, Scarlet with prime lens and 2 10,000 batteries I was at 25.5 pounds. Based on your description I don't think you would weigh that much. You might be better off with 16 inch props "if" you already have the 550 booms.

    I also see a few things that I would do differently if I were you.
    1. I would fix the lipo wires, the (+) and (-) wires need to be heat shrinked or taped together.
    2. I would relocate the Lipo batteries from above the flight control board to something like my configuration. Your CG will be way too top heavy.
     
  19. Nicholas A Donnelly

    Nicholas A Donnelly New Member

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    Dave- Gonna double check my weight this am and report back. I have 500mm booms so I guess 16" props are out? Regarding battery placement, can you share a photo of your setup?
    Thx
     
  20. Nicholas A Donnelly

    Nicholas A Donnelly New Member

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    Just did a prelim motor test to get temps. I guess the best way to simulate my payload is to throttle up to the average current draw (94a) while flying the epic?
     

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