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60110Re: [beam] help with a type 1 solar engine pummer...

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  • wrigter
    Aug 2, 2010
      Hi Keith,

      I don't remember this pummer design but it does not look all
      that effective.

      This circuit actually uses a combination of type 1, type 3
      and nocturnal SEs. The PNP transistor and SE circuit stays
      off while the solar cell is charging the battery (type 3).
      When the solar cell current drops at dusk, the PNP turns on
      and charges the 47uf cap (nocturnal) . If the battery
      voltage is higher than the trigger voltage of the 1381, the
      NPN turns on and powers the LED (or other load)(type 1).
      Positive feedback through the 100K resistor provides base
      current to the PNP and loads the solar cell output to latch
      the SE on. The load remains energized until the 1381 turns
      off when the battery voltage falls below the 1381 reset
      level. Alternatively the SE is also shut off, (ie at dawn)
      when solar cell output rises above the battery and starts
      recharging for another cycle and the PNP turns off.

      Since your solar cell output voltage is only 2.25V this is
      too low to properly charge two series nicad batteries (2.4V)
      required to power a red or green LED.
      Use two of these solar cells in series to raise the
      available charging voltage to charge two nicads.
      With one solar cell you can try a super cap instead of the
      battries but the LED on time will be greatly reduced. In
      addition the 1381 trigger level has to be chosen to be about
      be "somewhat" lower than the fully charged super cap or
      battery level (ie 2.3V for a 2.4V nicad and 2V for the super
      cap). If the load is a LED, a 82 ohm series resistor should
      be used to limit the LED current to about 10ma.


      ----- Original Message -----
      From: "Keith Anderson" <supernurseman@...>
      To: beam@yahoogroups.com
      Subject: [beam] help with a type 1 solar engine pummer...
      Date: Mon, 02 Aug 2010 21:42:26 -0000

      >Hi all.
      >I want to make my first pummer, using a variant of type 1
      >(1381 based) solar engine. (here's the link:
      >I have pretty much everthing I need except the 1381. My
      >solar cell is scavenged from an LED yard stake-light, and
      >puts out about 2v (it starts at 2.25v, and gradually drops
      >down to about 2.1v).
      >What flavor of 1381 do I need to get? Solarbotics suggests
      >a 1381g (2.4v) but another site suggests that a 1381j
      >(2.7v) is the most common. Does it matter? Is it related to
      >the output of the solar cell, or is it dependent on the
      >batteries? I also understand I can substitute a supercap
      >for the batteries (which I may do later...)
      >Any help appreciated.
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