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Power from the 'Super' moon

  1. Aug 10, 2014 #1

    nsaspook

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    This is last nights chart (from about 10PM to sunrise) into about a 3K load from about 500W total of panels. The hump at about 800 samples is where a separate panel of 120W started getting light from the moon. Maybe 20uW at max power. :biggrin:

    The DAQ is a Linux based NI-DAQCard-700 12-bit diff-input card using my kernel driver with a 128X oversample to squeeze a few extra bits of resolution.
     

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  3. Aug 10, 2014 #2

    jim hardy

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    Gives one a perspective for dynamic range of the eye, eh ?

    500 watts/20 uwatts = a ratio in incident light of twenty-five million- yet we see pretty well over the whole range.
     
  4. Aug 10, 2014 #3

    sophiecentaur

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    The Sun's apparent magnitude is around 27 and the (full) Moon's is around -13. That's a ratio of around 400,000:1.
    No hope of charging your phone at night then.
     
  5. Aug 10, 2014 #4

    jim hardy

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    Only 400,000 ?
    I'm surprised .

    But then, at 3K his solar panel probably wasn't loaded for power transfer.
     
  6. Aug 10, 2014 #5

    nsaspook

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    I'm sure it wasn't at the max power point voltage but that would still be only be a few uA of current at that voltage in the moon shine. The normal VMP is about 17.3vdc.
     
  7. Aug 11, 2014 #6

    sophiecentaur

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    That is just the ratio of the received radiated power (using the definition of stellar magnitude)
    m1- m2=-2.5log10(I1/I2)

    As the panel is not optimised for moonlight then you could expect anything, I guess.
     
  8. Aug 11, 2014 #7

    jim hardy

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    You know what ? I looked that up after your earlier post

    and keep getting 1016 for change from 27 to -13.....

    Am i mis-handling a sign ?
     
  9. Aug 11, 2014 #8

    sophiecentaur

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    The difference is 14 (I missed out the negative sign for the Sun's magnitude) and I was quoting from this Wiki entry. and I rearranged one equation to get the ratio on one side. I then quoted their answer but you are right about needing to get the sign right! I, naturally used the 'right value' when I slotted it in and got the 400000 answer. Negative magnitudes take you brighter and brighter as they increase negatively. It's not the intuitive way round but it relates to scoring the most visible stars as zero (Vega is the Zero point) and then the magnitudes increase as they get harder and harder to see. Seeing the bright objects like the Sun, obviously didn't count for the ancients.
     
  10. Aug 11, 2014 #9

    OmCheeto

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    A more interesting experiment would have you measure the no load voltages generated by the moon and sun. I discovered a while back that no load voltage is directly proportional to the amount of sunlight falling on a panel. The internal resistance of the panels makes it very problematic otherwise. For me anyways. :redface:

    I would do the experiment myself, but I don't have a meter that measures microvolts.
     
  11. Aug 11, 2014 #10

    jim hardy

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  12. Aug 11, 2014 #11

    sophiecentaur

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    You wouldn't have got it wrong if they were taking kVA, would you? That autopilot kicks to scrutinise the first answer you get with familiar quantities. I bet that's the first sum you did about stars for (cosmological) years.
     
  13. Aug 11, 2014 #12

    jim hardy

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    :rofl:

    first ever. Thanks again for the illuminating insight!
     
  14. Aug 11, 2014 #13

    nsaspook

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    I could get the full Voc for one Sharp 80W panel (about 21 volts) using just a Fluke 177 in full moon light but my high precision system filter network loaded it down to the recorded values.

    I changed my processing algorithm to cleanup the signal for last night but it started getting cloudy so you can see the changes in intensity due to the layer during the night in Oregon until my battery charger (from running a fan on the inverter to cool down in the house) auto-kicked in and ruined the rest of the data.

    I guess that's it for this cycle. :smile:
     

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  15. Aug 12, 2014 #14

    sophiecentaur

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    That post just clouds the issue - and moonlighting is taxable, you know.
     
  16. Aug 12, 2014 #15

    OmCheeto

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    I'm confused. Are you saying your panel put out 21 volts under no load illuminated just by moonlight? A Fluke 177 has a minimum resolution of 1 millivolt, so I'm having trouble interpreting that any other way.
    If those are millivolts on your y-axis, then it looks like your data is pretty much where it should be.

    ≈21vdc/≈400,000 ≈ 50 microvolts (your peak)
     
  17. Aug 12, 2014 #16

    RonL

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    Might be a good reason to check out the latest batch of MOONSHINE:biggrin:
     
  18. Aug 12, 2014 #17

    nsaspook

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    Yes. You can sometimes get full voltage from moonlight on a open circuit panel when measured with a high resistance DC meter (>10Mohm). The cooler the better to reduce leakage and the Sharp panels were some of the best made.
     
  19. Oct 8, 2014 #18

    nsaspook

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  20. Oct 10, 2014 #19

    dlgoff

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  21. Sep 9, 2015 #20

    nsaspook

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    Setting up a new rig for the Super Blood moon this month. I'll use a RPi2 this time for the data logger with another custom Linux kernel driver for the ADS1220 24bit ADC chip via the SPI port.
    Just finished up the hardware and software calibration with a old Omega CL511 calibrator.

    A few pics of the test setup and build.
    The home workshop is a bit of a mess but it's all working now.:smile:

    21295136251_0c796d0146_c_d.jpg
    21276445122_0be52a08cd_z_d.jpg
    Using a 4.998k load resistor for the solar panel and the calibration voltage adjustments @ 2000mV from the standard. The application program 'moonlight' logs the data to a text file with a time-stamp and sequential numbers for each reading so the data can be processed later.
    21225152262_f3918605c1_z_d.jpg
    ADC front-end board powered by two 9 volt batteries for a bipolar analog supply.
    The brass plates are ground plane/shields for the input filter and are connected to the metal box for (some) electrostatic shielding.

    From the program info header:
    * A special version for the TI ADS1220 SD ADC converter chip (and MCP3911 later) for low voltage sensing and
    * solar panel panel light detection. +- 2.048, 1.024 and 0.512 voltage ranges @ 20 bits of usable resolution
    * ADC is in single-shot conversion mode @20SPS, PGA disabled and gain from 1, 2 and 4 in differential
    * signal detection mode, 50/60Hz rejection enabled. 500kHz SPI clock with direct RPi2 connection
    * Analog +- 2.5VDC from Zener regulators for the bipolar input stage with external 2.5VDC Zener input
    * signal protection.
    Driver software: https://github.com/nsaspook/nidaq700/tree/master/supermoon

    20982519919_1101ef2432_b_d.jpg
    RPi2 with SPI connection to ADC with a breakout board to scope the signals while writing the driver.

    21276435932_370ecc34a2_z_d.jpg
    SPI data stream (clocks on the bottom trace) to the RPi2 in 24 bit format after a read command. It's a Delta-Sigma converter so the last few bits are just noise but 20bits are usable.
    21297000631_bb8cecb75e_z_d.jpg
    This should be in the micro-watt range during the full moon with a 5k load resistor.
     
    Last edited: Sep 10, 2015
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