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Re: Pummer Circuit Idea/Question(s) (kinda long)

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  • wilf_nv
    I will have more time later but here is a small contribution to the discussion. High peak supply current pulses are a major drawback of using 74HC240 inverters
    Message 1 of 5 , Mar 1, 2005
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      I will have more time later but here is a small contribution to the
      discussion. High peak supply current pulses are a major drawback of
      using 74HC240 inverters for construction an oscillator. Twice each
      cycle, the slow changing voltage at the R/C input node passes through
      the threshold and this is accompanied by a significant supply current
      pulse. The uPower CMOS oscillator

      http://groups.yahoo.com/group/beam/files/wilf_nv/uPower%20CMOS%
      20oscillator.gif

      overcomes this problem by buffering the CMOS input with a NPN
      transistor. This reduces the peak supply current by 2 orders of
      magnitude from several mA to several tens of uA.

      In this simple version the output is asymetric and is used here to
      drive a voltage tripler to drive a white or blue LED from a 2.5V dark
      turn on controlled solar charger using a super cap or two NiCd
      batteries.

      The voltage at tp1 and tp2 are normally high and low respectively.
      When the oscillator briefly changes state, tp1 and tp2 outputs go low
      and high respectively. This causes the two 1000uf caps to charge to
      2.4V with tp3 at 2.4V and tp4 and 100mV. When the oscillator changes
      back, tp1 and tp2 are high and low again while tp3 is "pumped" up to
      4.9V (max) and tp4 is "pumped" down to -2.4V (min). The difference
      between tp3 and tp4 is theoretically 7.3V, almost 3x the solar
      supply. In fact the LED will turn on and clamp this difference
      voltage to about 5V while the LED emits a fast rise, slow decay light
      pulse (pummm...)

      More ideas later.

      wilf

      --- In beam@yahoogroups.com, "Mike Scharf" <thelizard6969@h...> wrote:
      >
      > Good call. I had thought about that briefly. It sounds like exactly
      > the type of circuit that would work, although more costly it would
      be
      > VERY efficient. I just seem to have trouble making even the
      simplest
      > circuit operate using FET's. But that is one of my weaker areas
      that I
      > will be working on soon!
      >
      > Thanks Neil
      >
      >
      >
      > --- In beam@yahoogroups.com, "Neil" <neil@r...> wrote:
      > > Hi Mike,
      > >
      > > I think you are describing the holy grail of pummers here.
      > > One thought that I have had is to employ additional power in the
      form of
      > > a few series photodiodes.
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