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DoN. Nichols[_2_]

On 2011-11-22, wrote:
On Nov 21, 9:08*pm, "DoN. Nichols" wrote:
On 2011-11-21, wrote:

[ ... ]

I sometimes think about wiring up a "AAA" or solar cell and just
forgetting it, but for $0.50 a year it's not worth the trouble.

* * * * Actually -- there *are* some "solar powered" ones -- by Mitutoyo
IIRC. *They would probably be excellent used daily in a well-illuminated
shop.

I saw a solar-powered Mitutoyo at a flea market and was intrigued, but
resisted. Something about having a glass window on a machine tool
close to all that hard steel just didn't sit well--it brought up
memories of scratched and broken watch crystals.

I've seen them only new, and decided that in my shop conditions,
they would not work very well. :-)

OTOH, I paid $10 for most of my HF calipers. Those you can take
chances with. Using the 8x25mm solar panel from a $1 calculator, a
super capacitor for storage, and an LED as a regulator diode was my
notion. $2 in parts, $500 labor ;-).

O.K. Do you know the maximum voltage that the solar panel is
likely to produce? And the voltage drop on the LED? I know that
silicon diodes are typically between 600 mV and 750 mV. Also, any clues
as to the maximum voltage that the calipers can tolerate long term?

[ ... ]

* * * * I did recently get an auto-darkening welding hood from Harbor
Freight which is solar powered, and based on what I have read about them
dying if not used regularly, I've put mine on a folding workstool facing
out the window so it sees daylight to maintain the charge. *I'll proably
eventually have to perform surgery and replace the rechargeable cells in
there. *There is a temptation to provide a connection for an AC-powered
trickle charger so I can store it more conveniently. *What would be
particularly nice would be an induction coupled charger like those for
electric toothbrushes. *Just put it on a stand and expect it to be fully
charged when I come back.

* * * * If the charge is good enough to work on the first strike, it
should work fine for the rest of the day, because it will be getting a
charge boost from the arc -- close enough to vigorous sunlight. :-)

Sounds like a LiIon cell. If so, those can't be allowed to go dead,
as you've surmised.

And -- they are supposedly not replaceable according to the
manual. :-) (You've got to cut the package apart to get to them.) There
is a web page describing how someone opened one up and set a holder for
two AA cells outside the package. I'm really tempted to go for the
induction charger when I finally have to dig into mine. But it is
significantly less expensive than auto-darkening ones from MSC -- to the
point where three HF ones match the cost of one from MSC. :-)

Enjoy,
DoN.

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