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Thread: Teensy 4.0 results in small enclosure

  1. #1
    Senior Member
    Join Date
    Aug 2019
    southwest USA

    Teensy 4.0 results in small enclosure

    spacing in final post not what i had after pasting text in - not sure how to prevent that
    maybe i should attach a text file next time

    FYI - here are some results for T4 in a small sealed plastic box.

    Results are good even down to 4 cubic inches.

    tamb = 26-27 c, 1 hour soak, ir thermometer w 0.1 inch target dia

    all below: t4 running at 816 mhz fed w 5.0 volts

    situation iq top center cpu tempmon

    horizontal with small air flow ceiling fan 133 ma 48 c 61 c

    horizontal still air 139 ma 61 c 75 c

    inside sealed plastic box 4 cubic inch 143 ma 72 c 87 c
    top center box outside surf at 39 c
    816 is not usable but 720 is

    4 cubic inch box was 0.66 x 2.10 x 2.90 inch medium hardness
    plastic with 0.050 inch wall thickness.

    Although the tempco of iq is positive, there is not enough gain
    for a runaway (gain seems to be about 0.2).

    The variance with volume/surface area was small - 5 deg c
    improvement when vol increased to 11 cubic inch plastic.

    The variance with material was small - 7 deg c improvement
    when box matl 0.032 aluminum.

    Versus clock in 4 cubic inch plastic box, amb = 26-27 c, still
    air, box horizontal on plastic spacers, all numbers from
    tempmon (limit is 90 c):

      clock   no box    with box  allow amb c  allow amb f
       396     50 c       58 c            58           136
       528     54 c       61 c            55           131
       600     60 c       67 c            49           120
       720     67 c       78 c            38           100
       816     76 c       87 c            29            84  nil margin
    Direct sunlight on the box will subtract 10-30 deg f from the
    allow amb numbers. Here where I am, in the summer, 396 would
    be borderline so for outdoor use it would be best to provide
    a decent, short conduction path between the chip top surface
    and the inside wall of an aluminum box.

    Variance was +- 0.7 deg c from run to run and about +- 2 T4 to
    T4 giving an rss of +- 2.1 deg c.

    defragster edit: { added # / CODE block around table - that preserves some spacing elements }
    Last edited by defragster; 10-13-2019 at 09:01 PM. Reason: note about terrible final text spacing

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