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Protecting a circuit - ideas

Discussion in 'General Electronics Discussion' started by Will777, Sep 9, 2010.

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  1. Will777

    Will777

    31
    0
    Sep 2, 2010
    Hi,

    I have a FM transmitter circuit with exposed air wound coils - I have seen some ppl put a substance inside and over the coil to protect it - I've tried in vain to find out what this is - is it silicone sealer?
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,397
    2,777
    Jan 21, 2010
    Why does it need protecting?
     
  3. Will777

    Will777

    31
    0
    Sep 2, 2010
    The coil determines the frequency - so I don't want the coil to bend and change the frequency. Handling the PCB sometimes will bend the coil.

    Like this:
    [​IMG]

    Note the coils - is this silicone sealer?
     
    Last edited: Sep 9, 2010
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,397
    2,777
    Jan 21, 2010
    no idea, but adding this stuff will probably affect the operation of the device -- it may just require retuning, but you never know.

    Then again, considering how this has been built, I guess there's quite some leeway...
     
  5. Will777

    Will777

    31
    0
    Sep 2, 2010
    This is a sample of a bird's nest design I found on the internet try and show what I'm looking for - I built a kit on a PCB.
     
  6. LTX71CM

    LTX71CM

    182
    0
    May 23, 2010
    To me it always appeared to be a cardboard tube with wax holding it all together.
     
  7. Will777

    Will777

    31
    0
    Sep 2, 2010
    Cardboard? Inside the coil? Not sure if I see that?
     
  8. LTX71CM

    LTX71CM

    182
    0
    May 23, 2010
    Not in your example picture, in the radios I've taken apart throughout the years. Your photo appears to be hot glue or an epoxy.
     
  9. Will777

    Will777

    31
    0
    Sep 2, 2010
    Aah, I misunderstood.

    Cool - that is one idea. I suppose since the epoxy does not conduct it will be ok to fill the coil with that.

    Thanks!
     
  10. Will777

    Will777

    31
    0
    Sep 2, 2010
    I tracked down a very old post on another forum that confirms that hot glue works well - if anyone else has this same problem
     
  11. Zander

    Zander

    19
    0
    Sep 11, 2010
    A short between the coils maybe.

    Where do you get those variable capacitors? I can't find them on mouser.
     
  12. NickS

    NickS

    367
    0
    Apr 6, 2010
    I use hot glue regularly for dead bugging but when it goes on conductive areas we prefer DOW 3145 RTV because the circuit doesn't have to get very warm before the hot glue starts to run(among other reasons).
     
  13. Laplace

    Laplace

    1,252
    184
    Apr 4, 2010
  14. Will777

    Will777

    31
    0
    Sep 2, 2010
  15. Will777

    Will777

    31
    0
    Sep 2, 2010
    Thanks for the other two suggestions, will have to see what I can source locally as importing tends to be too expensive
     
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