Capacitor type selection for micro controller circuit

Discussion in 'The Projects Forum' started by pedro147, Oct 9, 2015.

  1. pedro147

    Thread Starter Member

    Jan 1, 2013
    52
    2
    I am working on building a flight control board from a circuit schematic that has been released under Creative Commons. The schematic and whatever information I can find in the Eagle libraries used in the schematic, are all the information that I have access too as well as a working commercial production example of the flight controller. I have developed an Eagle board file from the schematic, based as closely as I can to the production board. I have identified all the components on the board and the last step, which I would have thought the easiest is to source the ten assorted capacitors I have the package sizes and basic values but am confused as to which actual type of capacitors to use as there seen to be a large range of different types available. Here is a link to the Eagle schematic and an image of the circuit and close up of the top of the board. Any advice as to capacitor type, voltage and the like would be greatly appreciated thanks. Sorry about the messy list:)

    • Number Value Package
      C1 1uf 0603
      C2 1uf 0603
      C3 1uf 0603
      C4 0.1uf 0603
      C5 0.01uf 0603
      C6 0.1uf 0603
      C7 0.1uf 0603
      C8 2.2nf 0603
      C9 10uf 0805
      C10 10uf 0805
    Alienwii Schematic.gif

    Alienwii closeup.jpg
     
    • AW.zip
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    • AW.sch
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  2. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    They are ceramic. There is no voltage above 3.3 volts on the board except for one capacitor at 3.7 volts. That one is available at 4 volts or 6.3 volts. The voltage I see most is the 6.3 volt capacitors. If you can do them all in 6.3 volts, that seems like a good safety margin. If Mouser is not in Australia, pick a different vendor after you see how the parametric search page works.

    http://www.mouser.com/Passive-Components/Capacitors/Ceramic-Capacitors/_/N-5g8m/
     
  3. pedro147

    Thread Starter Member

    Jan 1, 2013
    52
    2
    Thanks a lot #12. Yes the circuit is powered by a 4.2 volt Lipo battery and most of it is regulated to 3.3 volts as you say. So if I use 6.3v caps as you suggest I should be good to go. For interest, which cap is seeing 3.7v please and how do you deduce that - just so I can learn something else for the day :) Once again thanks a lot for you help and have a great day.
     
  4. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    C10
    The battery is labeled, "3.7 V" on the schematic.
    You called it an, "image".
     
  5. pedro147

    Thread Starter Member

    Jan 1, 2013
    52
    2
    It's not my schematic :) Unfortunately I am not that clever, just trying to make a board from it. I see what you mean - C10 on the board before the 3.7v goes into the voltage regulator. Thanks for helping and teaching me something today
     
  6. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    Changing that voltage by that amount will increase the power dissipation of the regulator chip, so run the math to be sure it won't overheat.;)

    and pay attention to that symbol on top of U3. It says 2.2 uf but it's an inductor.
     
  7. pedro147

    Thread Starter Member

    Jan 1, 2013
    52
    2
    Thanks for taking an interest #12 that is very generous of you. The board has been in successful production for over a year but it has not been without a few problems, although it's performance from a purely flying point of view is outstanding and well received within the quadcopter community. The inductor appears to be http://au.mouser.com/ProductDetail/Taiyo-Yuden/NR3015T2R2M/?qs=/ha2pyFadujPTGuvYgDxkrx3eBFanGY1QWzQrHFZHiCzhwLa/hG8lA== Doing the maths for the power dissipation in the regulator is beyond my abilities at present, not the actual maths but the overall procedure on how to calculate it. There has been no apparent problems with the voltage regulation only that the mosfets can fail when used with certain high performance motors. The designer upped the specs of the mosfets from 4.2 amp to 6.3 amp but as I say the problem with the higher performance and hence higher current drawing motors can rear it's ugly head.
     
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