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WiFi overheating issues: Don't forget the Range Extender.

Discussion in 'Phantom 2 Vision + Discussion' started by CapnBob, Dec 19, 2014.

  1. CapnBob

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    Much has been said (and done) here about the P2V+s WiFi module and the heating issues.
    That is only half of the equation. The Range Extender is the other half.

    Both units use the same Atheros chipset, operate at the same power, and have the same issues.
    The extender board, being in a small box with no ventilation, may be even more prone to overheating.
    My RE gets quite warm on the outside, and that's just convection heating from the board to the case.

    I will not get into the disassembly to the board level here; this is for meant for those who already know that process.
    If you do not know how to disassemble the units, there are threads here as well as YouTube videos showing how this is done.

    in both units, there is a ~.020" gap between the output stage ICs and the RFI shield/heatsink.
    Some have filled this gap with Thermal Compound. This is better, but by no means ideal.
    Aluminum is a much better conductor of heat than TC; the compound is intended to fill small air gaps, not as a heat sink in and of itself.

    I believe this is a better solution.
    Use household aluminum foil, and fold it and/or add single layers to get a ~.020" thick shim a bit larger than in the images below
    (My foil is .002" thick, yours may vary)
    Put a tiny dab of TC between layers to stick them together...
    If you have any doubt, go thicker rather than thinner, as this will help to mechanically retain the shim between the ICs and the shield.
    Cut the resulting shim to final size.

    Make a paper mask larger than the shim and make cutouts for the 2 ICs. This will insulate the shim from the board components.

    Place the mask on the board, apply TC to the 2 chips, and press the shim into place. Add TC to the top of the shim, and reinstall the RFI shield/heatsink

    In informal tests with an IR gun, the module's case got hotter quicker, which tells me more heat is getting out of the chips faster.

    All else being equal, hotter case=cooler ICs.

    Bird WiFi Board:


    Range Extender WiFi board:
     

    Attached Files:

  2. erikgraham

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    Re: WiFi overheating issues: Don't forget the Range Extende

    Your the man Cap'n Bob!

    What do you think about drilling holes or cutting vents into the Rang Extender's case?
    Obviously one would have to be more careful of moisture getting in, but the extra ventilation should help things stay a bit cooler.
     
  3. MapMaker53

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    Re: WiFi overheating issues: Don't forget the Range Extende

    Having not ever worked with TC, I see it being listed as various products - some specified as being non-conductive. Which type should be used? I also was about to ask about sawing a row of vent slots in the plastic housing.
     
  4. CapnBob

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    Re: WiFi overheating issues: Don't forget the Range Extende

    I considered that, and I'll probably do it.
    The way I see it, holes in the case would be a non-issue. The bird's shell is vented, so if it's ok to fly her, you won't get any wetter than she will. ;-)

    As the Extender's "face" should be tilted up towards the bird, I will probably put the holes in the back panel, near the top and bottom to get a chimney effect.

    I just want to get another few flights to evaluate these mods first.
    I think we're moving in the right direction.
     

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  5. CapnBob

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    Re: WiFi overheating issues: Don't forget the Range Extende

    It's very much personal preference. Some swear by "Arctic Silver", but I'm old school. I am a retired EE, and I don't want any metal particles that could possibly do dastardly deeds. I use a Boron Nitride-based product by MG Chemicals called "Super Thermal Grease". Boron nitride has nearly the equivalent thermal conductivity as a metal, with none of the electrical conductivity.

    B.T.W., there are "Name Droppers" that swear one is much better than another, but a study was done on nearly 80 TCs, and from the top of the list to the bottom of the list in performance, the temperature difference was +/- 2.5° from the median. Using one over another will neither insure from nor cause thermal failure.

    Use what you want. just use something.

    Oh, and the correct Engineering Speak for Thermal Compound is "FWS" (F*****g White Stuff) ;-)
     
  6. burlbark

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    Re: WiFi overheating issues: Don't forget the Range Extende

    This should be a good mod. One thing to remember is that the onboard wifi module is sending a tremendous amount of data compared to the wifi extender. Anything to keep everything running cooler is a good thing.
     
  7. RichWest

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    Re: WiFi overheating issues: Don't forget the Range Extende

    CapnBob - Great stuff, I appreciate you pointing out the guts of the RE is basically the same as the bird's wifi module. I had wondered why the RE didn't overheat like the wifi module, I believe it because there is less heat producing hardware in the RE = less convection temps. Surprisingly the housing itself is able to dissipate much heat. The battery side does get warmer on my unit and now is overall less having installed stage 3 antennas.

    Not questioning your solution, but to what level of heating does the output stage ICs get in your opinion in the module? From an example test, I removed the wifi module's cover and set temp. test probes directly on both the Atheros chip and the emi shield. Neither had TIM applied. The test was 15min, which produced interesting results. 118F on the shield and below 130F for the Atheros chip. With +20% of the Atheros chip under the emi shield, I believe convection from that chip produced the heat rise on the emi shield for this test. That’s why I didn’t run further test with TIM for the emi shield or the chips below. Just curious for the conversation about my assumptions. Personally I think DJI mistakenly applied TIM to the emi shield….conduction from the cover and then convection thereafter within the entire module.
     
  8. CapnBob

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    Re: WiFi overheating issues: Don't forget the Range Extende

    Those numbers don't jibe. If only 20% of the Atheros chip is under the shield not touching it, and air convection is cooling it. how could the shield reach 90% of the chip's surface temp? There are 2 output stage ICs under the shield which what this mod is about. There are reports of the shield becoming discolored from heat above these ICs. I'm running my modules at 60mw and those chips get too hot to touch. I would suggest you disassemble the unit, remove the RFI Shield, and measure the 2 output chips.

    "A stitch in time saves 9", and a WiFi module is $190

    There is a detailed thread on this problem here viewtopic.php?f=27&t=28176&hilit=wifi+failing
     
  9. RichWest

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    Re: WiFi overheating issues: Don't forget the Range Extende

    Thanks for the reply, I didn't calculate the difference as %, but yes I would have to agree. I will test those chips at some time in the future, but currently I'm bolted down and just flying. I got a little "burnt" out with all the testing I did.

    Further, I am by no means saying that I'm right about anything I've discussed or questioned, just trying to learn from the exchange to make what I have perform better. "Necessity is the mother of invention."
     
  10. Nathan Carter

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    Re: WiFi overheating issues: Don't forget the Range Extende

    Anyhting that the onboard wifi module is sending goes to the wifi extender and gets sent by it to your phone/tablet. So they are under equal load.
     
  11. burlbark

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    Re: WiFi overheating issues: Don't forget the Range Extende

    No they are not. I could have worded my first post better. The data stream coming down from the phantom is significantly greater than the command line being sent back to the bird. The output of the wifi extender to your viewing device is much less in strength, less power, less heat, less load.

    How far does the wifi extender have to transmit to reach your phone? 15-20 feet max range.

    How far does the Phantom transmit to reach your wifi extender? 600-2500 feet.
     
  12. CapnBob

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    Re: WiFi overheating issues: Don't forget the Range Extende

    T/R. The same power. Data stream does not come into it.
    The power issue is in the carrier, not the data stream.