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Booting the Prop from low voltages, 3 of 3: Meyer Lemon @ 0.42V — Parallax Forums

Booting the Prop from low voltages, 3 of 3: Meyer Lemon @ 0.42V

TubularTubular Posts: 4,718
edited 2011-08-01 01:59 in Propeller 1
As Mark_T correctly guessed, the final energy source in this LTC3105 series is the humble lemon.

The lemon by itself didn't provide enough "juice" (current) to boot the prop. It needed a "lemon-aid" in the form of a cap/supercap to charge up to 0.42V before the LTC3105 could work its magic.

The two electrodes I used were a strip of single sided copper clad pcb material, and a #14 gauge galvanized bugle bolt. This produces a potential difference of about 1 volt. The short circuit current I measured at about 600 microamps initially, but it reduces as the reaction progresses.

Charging the 0.9F supercap took something like an hour, before the voltage read 0.42V. The LTC3105/Prop combo was then connected, booted, and operated (flashing a blue led in RCSLOW) for about 2 minutes before the cap voltage dropped below the minimum 0.32V.
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Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-31 18:42
    I guessed a Eureka lemon, which accounts for 48% of Australia's lemon crop. Ah, well, even with the percentages in my favor, the truth sometimes evades my grasp. :)

    -Phil
  • TubularTubular Posts: 4,718
    edited 2011-07-31 19:16
    An excellent guess Phil, and I must admit I would have loved it to be a Eureka for its exclamatory qualities.

    But as truth would have it I'm stuck with a Meyer tree, overflowing with fruit despite the busy efforts of the citrus gall wasp.

    At least I have a good use now for all those lemons in powering prop circuits, or testing LTC3105 boards.
  • Cluso99Cluso99 Posts: 18,069
    edited 2011-07-31 23:20
    Aha! I see a Christmas light lemon tree, but instead of the globes, I see they are connected to copper and galvanised nails plugged in pairs into each lemon on the tree :)
  • Heater.Heater. Posts: 21,230
    edited 2011-08-01 00:24
    Years go, back in southern England, l could get enough power to turn a motor from a copper strip a galvanized strip an a glass of water straight out of the tap!
    Admittedly this was an exceptionally small geared motor and it could only just rotate an attached cocktail umbrella but I hate to think what we were drinking everyday then.
    Booting the Prop would have been a doddle.
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2011-08-01 01:59
    Re drinking water,

    Back in 1990 we were being moved out of the dedicated OB base and back into the studio block and I happened to be out in the garage when this guy from the water board turned up. He asked to read the meters, at first I just told him where they were but then turned back and enquired what he meant by "meters". He then explained that we had two sorts of water supplies, one was domestic (drinking) and the other was industrial.

    I then realized that for the previous eight years the water that we had taken up the Welsh hillsides for teas and coffees was the stuff directly from the local docks. Probably explains a lot.

    (As for lemon power, I was told a while back to stop being so exotic, and use spuds instead)
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