The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Month: September 2009

  • Hobo Data Logger Current

    Hobo battery current tap
    Hobo battery current tap

    A comment to my note on hacking AA alkalines on the back of a Hobo data logger (from someone at Onset!) suggested checking the logger’s current.

    After dumping last month’s data, I conjured up a piece of double-sided circuit board and soldered a turret terminal to each side. It’s thin enough to fit between the cell’s positive cap and the holder’s contact without distorting things too much.

    The lowest range on most of my digital meters is 200 mA, which is far too high. I tried an ancient analog meter with a 50 µA range, but the meter’s resistance was too high to keep the Hobo’s PC program happy: it claimed there was no logger out there. Finally I found a digital meter with a 4 mA range and 1 µA resolution, which was just right.

    Turns out that the logger draws 8 or 9 µA between readings, which is pretty much what it should be. At that rate, a CR2032 lithium coin cell with a capacity of 230 mA should have a lifetime of 23 k hours: call it three years. Obviously, it’ll be less than that, what with periodic loggings and dumpings and suchlike.

    The current’s the same with the external temperature probe plugged in and doesn’t change when I poke the capacitors. So the logger seems to be working perfectly.

    Which means I got a bad batch of Renata CR2032s two years ago. I just pulled one from another logger that I installed 5 Feb 09: all of six months ago. If I installed a series of really feeble cells in this logger, well, that would explain what I experienced.

    I’m currently using Energizers in the other loggers, so we’ll see what happens a year from now.

    But I’ll keep the alkalines on the back of this logger, as they should last basically forever at this rate.

  • Phone Headset Pinouts

    I picked up a Plantronics phone headset that’s nominally compatible with Kyocera phones, but of course not with the Virgin Mobile K127 Marbl I have. More on why I have that phone there. There are, as nearly as I can tell, no third-party headsets available for this phone.

    The Plantronics headset has the pinout shown to the upper right in the note below. It’s straightforward:

    • shell — common
    • ring 1 — left audio
    • ring 2 — right audio
    • tip — mic + button

    Plugging the headset in causes the phone to throw a hissy fit.

    Jamming an open-circuit plug into the phone’s jack has no effect; the phone thinks there’s nothing going on and still routes the audio to the internal speaker.

    Evidently, the phone expects a different combination on the plug.

    Some Webbish rummaging produced a list of headset pinouts, which goes to show that there’s nothing like having enough standards that everybody can have one…

    Headset Pinouts
    Headset Pinouts

    More tinkering is in order, but I found this list while I was clearing away the rubble from some completed projects and figured I should put it somewhere obvious.