> Why a single AA cell. Do you mean eg Alkaline (Le Clanche) as
> opposed to Lithium?

Did you mean to indicate "Alkaline OR Le Clanche", as an 'Alkaline'
cell is certainly *not* a Le Clanche cell ...

  George Lechanche of France developed what turned out to be the
  forerunner or the world's first widely used battery: the zinc-
  carbon cell in the 1860's.

continung to quote:

A commercially produced battery is called the Le Clanche cell.

An example of this is the silver colored Eveready  nine lives  battery.

In this reaction the zinc casing on the bottom of the battery also
provides the zinc reactant. The zinc solid is oxidized to Zn2+ as in
the Daniell cell. The reduction half reaction involves a paste containing
MnO2. Mn has a 4+ charge in MnO2 and by gaining one electron, it is reduced
to Mn3+. In the center of the battery is a carbon rod to conduct the
electrons. That rod is carbon (graphite) and is the same graphite that is in
your pencil (no lead in your pencil). It also makes the bump at the top of
the
battery.


- - - - - - - - - - - -

RF Jim



----- Original Message -----
From: "Russell McMahon" <apptech@PARADISE.NET.NZ>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, December 17, 2002 3:08 PM
Subject: Re: 1 AA Cell powering PIC/LCD


> > Need a good way to power a PIC ('877) and a LCD (no backlight) from a
> single AA cell.
> >
> > There are about 18 billion different switched regulators out there and I
> can't seem to figure out which is best for
> > this application.
> >
> > I'm expecing to draw around 4 mA running, and need to last a long time
> quescent.
>
>
> To help refine the answer, please answer the following (in triplicate on
> form 922(b) ...)
> You can expect an "OK" answer without knowing all the following but all
the
> following will help to get it really right.
>
> One off or many off?
> How many off?
>
> How cost sensitive?
>
> How size/weight sensitive?
>
> How important is efficiency of energy conversion?
> (50% OK, 80%, 90%, 95%)
>
> Why a single AA cell. Do you mean eg Alkaline (Le Clanche) as opposed to
> Lithium?
>
> What voltages do you want / need?
> Is PIC run at lowest possible power (3v 32 kHz) or at ???
> (4mA expectation gives an indication)
>
> Is this run 24 hours/non stop or turned on and off as required?
> What is duty cycle?
>
> and more ... ?
>
> ______________
>
> Say its 4v mean needed at 4 mA (Allows some extra for LCD etc)
> 4v x 4mA = 16 mW
> Assume alkaline AA = 3000 mAH.
> Voltage = 1.5v start down to say 1v endpoint (0,9v OK but not too much
> energy left).
> Assume mean voltage of say 1.2V (curve droops faster at top)
> 3000 mAH x 1.2v = 3600 mWH available.
> 3600/16 = 225 hours at 100%
> Say 200 hours to be safe.
>
> 190 hours at 95%
> 180 hours at 90%
> 160 hours at 80%
>
> About 7 to 8 days continuous 24hrs/day.
>
> ______________________
>
> Depending on answers above I'd consider either a Roman type 2 transistor
> circuit or the 2 transistor multivibrator cct I posted within the last
week
> (slightly more parts, more "designable")  OR one of the purpose built
single
> cell inverter IC's on the market or just possibly a capacitor pump (but
> provably not).
>
> MAX1678 is a good example of a typical single cell to 5.5v max inverter
IC.
> As its available ONLY in their micromax package (SMD 0.65mm pin spacing)
it
> may not suit your need but otherwise it appears an excellent choice (I've
> never used one myself). Synchronous rectification so high efficiency and
> lowest possible parts count (IC, coil, 2 x cap (1 each at input and
> output)), tiny. Starts on 0.85 volt. 37 uA quiescent or about 2uA on logic
> shutdown.
>
> ________
>
> In comparison my multivibrator needs two transistors, 3 resistors,
inductor,
> diode, zener, 4 capacitors (in, out, 2 x timing) and gives lower
efficiency.
>
> ____________
>
> Then something like the "Joule thief"  (Google will find) may suit your
need
> with some regulation added.
> .
>
>
>
>         Russell McMahon
>
> --
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>

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