I WAVER QUESTION

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    • December 14, 2004 at 2:34 am #12455
      jamiekulhanek
      Participant
      • Posts: 2563

      hey,

      Just wondering if anybody has had any luck running a motor such as a atamiya plasma dash in the iwaver “pro chassis, using the stock FETs…

    • December 14, 2004 at 2:09 pm #57531
      ph2t
      Participant
      • Posts: 2088

      see here, this bloke just put a crappy iWaver XSPEED motor in it and it blew. IT wasn’t even the Xspeed Pro, just the regular iWaver xspeed.

      http://www.microrccenter.com/forum/index.php?showtopic=30978

      So I doubt it would work.

      I think their statement is full of shit. I’ve yet to see any complementary mosfet SO-8 pkg that can take over 2-2.5W of power….. Given this limitation unless they go to single packaged MOSFETS I reakon….

      “Tell ‘im he’s Dreaaaaaaaming…..”

      ph2t.

    • December 14, 2004 at 2:36 pm #57533
      Avatar photoAaron
      Keymaster
      • Posts: 2146

      I doubt they’re using great FETs, the heat load due to high internal resistance being a problem.

      I would think that a pair of IRF7317s or a mini-FET swap, or a full on Nelly will wipe the floor with TE FETs.

      Has anyone gotten part numbers off their FETs or the 16pin TSSOP yet?

      A.

      --
      Site Owner Guy.

    • December 14, 2004 at 3:47 pm #57535
      ph2t
      Participant
      • Posts: 2088

      I’ve got the part numbers at home for the IW02 mosfets. The iw-01 pro’s apparently have the faces grounded down. Dodgy buggers….

      I’ll post the part # tonight for the IW02, it’s an IRF mosfet I can tell you at the most for now.

      ph2t.

    • December 14, 2004 at 4:01 pm #57536
      Avatar photoAaron
      Keymaster
      • Posts: 2146

      Thanks dude!

      A.

      --
      Site Owner Guy.

    • December 14, 2004 at 4:29 pm #57537
      ph2t
      Participant
      • Posts: 2088

      no wucca’s!

    • December 15, 2004 at 4:38 am #57548
      ph2t
      Participant
      • Posts: 2088

      here’s the dilly…

      the mosfets used on the IW02 pcb’s are IRF7338

      here’s the datasheet:

      http://www.irf.com/product-info/datasheets/data/irf7338.pdf

      Max power dissipation is still only 2W.. The on resistance is pitifull stock mini-z HAT3004 mosfet quality.

      cheers,

      ph2t.

    • December 15, 2004 at 1:47 pm #57550
      Avatar photoAaron
      Keymaster
      • Posts: 2146

      Yikes, now there’s a SH!T pair of FETs!

      With internal resistance of about 210mOhms – basically double that of a IRF7389, and MORE THAN THREE times higher than the IRF7317 these iWaver Pro’s are not going anywhere fast.

      The internal resistance means that those puppies are going to overheat (the dissipation ph2t mentions) real quick…

      A.

      --
      Site Owner Guy.

    • December 15, 2004 at 3:28 pm #57554
      peteWah
      Participant
      • Posts: 1020

      More than a yikes, Its a >steer clear it sounds like Chief

    • December 15, 2004 at 8:49 pm #57567
      jamiekulhanek
      Participant
      • Posts: 2563

      What I want to know is why the hell do they use S0-8 package FETs??

      I never believed the data sheets for the 7389 and the 4562’s, 7A from a tiny S0-8?? I don’t think so Tim…..

      In theory my 9×2 stack of FETs should have handled ~50A…..but nope, 10A was almost too much…

    • December 15, 2004 at 9:26 pm #57569
      Avatar photoAaron
      Keymaster
      • Posts: 2146

      It’s correct when used to manufacturers specs. Whilst we only focus on working ability and RDS(on) there’s more at play including getting enough gate voltage to properly switch the devices, if the switching circuitry is average then the FETs themselves will not perform to spec.

      I’d guess that the Mini-Z electronics doesn’t switch fast enough to control the FETs correctly and that causes them to suffer more load/heat stress than is desirable. I woudl think moving to matched FET drivers (like Nelly 1.3?) will get around this..

      A.

      --
      Site Owner Guy.

    • December 15, 2004 at 10:06 pm #57570
      ph2t
      Participant
      • Posts: 2088

      yup, lower internal resistance decreases power dissipated. that’s the theory anyway…..

      ph2t.

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