Spraying the mikrokopter boards

Discussion in 'Electronics' started by Lauri Hakala, Sep 27, 2012.

  1. Lauri Hakala

    Lauri Hakala Member

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    Any advice which parts should I mask out when spraying the boards for better humidity tolerance? Of course the connectors but is there anything else? Thanks!
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    The pressure sensor (with the Velcro that I presume you have attached) on the flight control board.

    I wouldn't spray the heatsinks on the PDB if you have those mounted. I had them mounted so I didn't have to ponder whether or not to spray the top surface of the MOSFETs on the PDB -- I would be concerned that the spray would reduce their ability to dissipate heat.

    As part of the applying the heat sinks with Arctic Silver, I had encased the MOSFET leads in silicon adhesive so they were already insulated against moisture -- but if you don't have the heat sinks on the MOSFETs be sure to give those leads two coats -- the input impedance of the MOSFETs are very high (because they're MOSFETs!) which makes them very susceptible to moisture. If you're not sure what a MOSFET is, think "big transistors" :) . The arrow heads point to the MOSFETS. The square shapes are the tops of the MOSFETs, the silver things on the other side of the MOSFETs (three per MOSFET) are the leads. (What's a MOSFET? See http://en.wikipedia.org/wiki/MOSFET).

    PDB MOSFETS.png

    If you have the Smart OSD board, then don't spray the two adjustment potentiometers.

    While it's not necessary to avoid spraying the pig-tail wires on the PDB (that connect to the motors), you'll find that the conformal acrylic crazes when the wires bend and starts to flake off them, so you might want to mask them off just because the acrylic looks pretty crufty when it crazes.

    Also, be sure to mask all sides of the USB connectors (there are some gaps through which the spray could otherwise reach the connectors). Also, mask off all sides of the SD card connector for the same reasons.

    While you're doing this, double check that the big capacitors on the underside of the PDB are secure. On my RTF C8 I found one that had come loose. Hot glue!

    I chose not to spray the GPS antenna (the top surface of the GPS board). Why? Just on hunch.... I did spray the underside of the GPS board though and both sides of all other boards.

    Later on, if you need to come back and solder on leads for power to the PDB, you'll find that acrylic coating just burns off with the heat of a soldering iron.

    Hope that helps.

    Andy.
     
  3. Lauri Hakala

    Lauri Hakala Member

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    Thanks for the fast an in detail response! I'm so happy because you just answered to all my questions - slowly getting deeper in multirotor world :)
     
  4. Josh Lambeth

    Josh Lambeth Well-Known Member

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    This is great info.. I will be doing this soon.

    Josh
     
  5. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Thanks, Josh. I just had to figure it out from first principles and knowledge of working around computers for a couple of years or so.
    Which is my way of saying that the warranty on the above procedure is even shorter than a Harbor Freight tool warranty. ;) (Sorry -- U.S. cultural reference.)
    Andy.
     
  6. Josh Lambeth

    Josh Lambeth Well-Known Member

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    Whats the best type of spray to use?

    Josh
     
  7. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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  8. Tommy - KnightDesignDev

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    Altimeter, Fets, Antenna, buzzer, Flash, battery, and keep off wire insulation jacket.

    For coating, Agree with Andy. Many years in Class-3 Military Electro-mechanical Manufacturing has taught me a few tricks. Good masking is key, and watch for wicking. We use Turbo-Coat™ Acrylic Conformal Coating because of quick dry / easy masking release / blacklight inspection / and all the same items Andy noted. The Fine-L-Kote is great because you can spray it into a dixie-cup and brush on touchup spots. Both great stuff.

     
  9. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Thanks for confirming. I didn't realize that Turbo-Coat had a UV indicator -- that makes it much easier to see that you've got good coverage -- and 10 minute cure in elevated temps.

    Andy.
     
  10. Wolfgang Armin

    Wolfgang Armin Active Member

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    Hi Guys,
    first of all: thanks for the tips and listing the items that should be masked. I just received my Turbo-Coat.
    I still hesitate on starting the coating procedure because not being a native english speaker, those tec-terms are hard to follow.
    Would anybody be willing to draw a "mask" on an image if I provide pictures of all the items (powerboard, FlightCtrl, NaviCtrl, GPS)?
    Just like this example here (being a photographer I would do better, but this was what I already had at hand ;-))
    It´d be more than appreciated![​IMG]
     
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  11. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Wolfgang:

    Sure : I was just about to start working on a short video this weekend and this may be an alternative way -- please be sure to send images of both sides of the boards -- the exception being the GPS board -- only send an image of the underside of that as I did not spray the top side where the antenna is located.

    Can you take the images from directly overhead, Wolfgane? It will make it easier to show the masking without having to work in perspective.

    The best way to get the images to me would be if you could create yourself a free Dropbox account (www.dropbox.com) and upload them into your public folder and send me the links.

    I use Photoshop CS6 so you can send RAW images if you want.

    By the way, it looks like you may have a loose capacitor for Motor #1 -- the one that is closest to the square hole. Be sure to check that that is mounted solidly -- you can use hot glue to secure it.

    Thanks
    Andy.
     
  12. Wolfgang Armin

    Wolfgang Armin Active Member

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    Hi Andy,
    coooooooool - thanks a big lot! Sure I´ll do it directly overhead - this was just a quick shot when I sold this powerboard.
    Yeah, there´s a lot of damage on it - it was a huge crash, but I´m flying with a new one ;-).

    I´ll try to get it done tomorrow noon.

    Cheers,
    Wolfgang
     
  13. Wolfgang Armin

    Wolfgang Armin Active Member

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    OK, done - there doesn´t seem to be something like PM on this board so I wrote you something that´s called "profile post".
    Didn´t want to write the link here because if I´m going to delete the file it would be awkward for people in the future.

    Thanks again, looking forward to spraying away ;-).
     
  14. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Sorry, Wolfgang. I can see "Profile post" for you, but no message.
    There is something called "Start a Conversation", or you can email the link to me at ajohnsonlaird AT me.com

    Andy.
     
  15. Wolfgang Armin

    Wolfgang Armin Active Member

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    Hmmmm - didn´t find the "Start a Conversation" thing - just sent you an email. Hope I´ll not end up in the spam folder ;-).
    Cheers,
    Wolfgang
     
  16. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    To get to Start a Conversation, ciick on my name where it appears above the words Flight Squad to the left of any of my postings.
    Nicely hidden, isn't it? :)

    Andy.
     
  17. Wolfgang Armin

    Wolfgang Armin Active Member

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    That´s weird - I did that several times (at least I think so) and was always redirected to your profile page. Now it works for me too.
     
  18. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I'm happy to announce, with help from Wolfgang, I have created a 14 page document that describes how to mask off the MK Boards and spray them with conformal acrylic spray.

    The document has the riveting title of: A Rather Good Guide™ For Spraying the Mikrokopter Boards with Conformal Acrylic Spray.

    You can find it by going to rathergoodguides.com then selecting Document Guides and you'll see the link to the PDF file. I'd give you the direct link, but it seems like there is something weird going on with DNS when you try to go directly to it -- sometimes it works, sometimes it doesn't.

    Enjoy.
    Andy.
     
  19. Wolfgang Armin

    Wolfgang Armin Active Member

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    Thanks Andy, that´s exactly what I was hoping for. Perhaps this should be posted in a separate sticky thread! Very well done!
     
  20. Josh Lambeth

    Josh Lambeth Well-Known Member

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    You sir are awesome!!!

    Thanks for this!

    Josh
     
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