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Continuous power dissipation at room temps?

  • NightRider Wednesday, May 09, 2018 6:25 PM Reply

    I need the to continuously operate these as power loads at 12V which translates to P=V^2 / R = 12*12/15 = 9.6W.

    I'm sure these resistors can't handle the max specified power dissipation continuously. I usually allow 25-50% of the specified max.

    Anyone know where to find the data sheet or has experience with these long term?

    The problem is that these are the only ceramic power resistors available at DX so I have to make do with what's available.

    Of course I can connect them in series/parallel configuration (2S2P) to increase power capability but since I need 8 such loads, quantity will climb to 32 units and will require a much larger package.

    Maybe I'll try to couple them to a suitable heatsink though total power of 80W will require forced air cooling.

    Cheers.

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    post edited by NightRider on 5/9/2018 at 6:38 PM
  • sheepish Top 10 Forum Poster Wednesday, May 09, 2018 7:37 PM Reply

    I'm sure these resistors can't handle the max specified power dissipation continuously.


    And being that brand, I would not be at all surprised if they could only handle 2 or 3 W continuously. Zhaoyao is a company of bald-faced liars.


    That aside, what are you trying to do now? Run a car heater?

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  • matrix-neo Moderator Wednesday, May 09, 2018 9:36 PM Reply

    just an idea, if you need a lot of cheap low(ish) resistance buy nickel or nichrome wire on a roll, measure resistance per length then cut as needed and coil wire, if heat is an issue cover with silicone tubing or hi temp heatshrink

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  • sheepish Top 10 Forum Poster Thursday, May 10, 2018 6:31 AM Reply

    Trapping the heat doesn't help it dissipate.

    DX has found a new way to deceive customers:
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  • matrix-neo Moderator Thursday, May 10, 2018 12:33 PM Reply

    yes i know but by heat i meant if it comes in contact with flammable material you want to prevent a fire

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  • sheepish Top 10 Forum Poster Thursday, May 10, 2018 3:47 PM Reply

    With a coating on the wire there will still be the same amount of heat to dissipate. After the extra thermal mass has heated up the extra surface area on the coating compared to the wire might mean it manages to be a little bit cooler, but depending on how thermally conductive the coating is, the ends of the wire might end up hotter, which might pose a greater risk.

    DX has found a new way to deceive customers:
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  • matrix-neo Moderator Thursday, May 10, 2018 9:40 PM Reply

    scratch the coating idea, i'm assuming the customer won't be covering the ceramic resistor so the homemade resistor won't need it either

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