Not so. A lot
of machines use the NiCd as the smoothing component. HP
certainly did in just about all of their more recent NiCd calculators (the
ones that use the 8V 50mA AC charger).
Interesting. I haven't found where the battery gets in, but the input
stage is something like:
Diode
Ring --+--/\/\/-|>|-+-----+
| 56R | \
| |C / 82R
| |/ \
+-/\/\/-+--| NPN /
| |\ |
_ |E |
Tip--+ Zener A +-----+--- +5V? to rest of machine (??)
| |
GND GND
I would guess the battery could well do any smoothing downstream of the
regulator, but I'd still like to see some upstream of it!
That looks like a voltage regualtor, which is strange, since I'd have
expected a constant current charger for the NiCd. Of course a lot of
machines just use a resistor to limit the charging current (and to get you
to buy more expensive battery packs)
If the machine draws 60mA, minimum voltage at input is around 9V,
maximum around 13V, so I suppose I could try 10V and see what happens...
Remember that you'll be charging this thing (probably) with the machine
turned off, so it's not going to be taking much current).
Some, like the Epson HX20 even used the fact that
the voltage across the
NiCd would go above 5V to limit the supply voltage to the chips. The
^^^^^
I take it you mean wouldn't
Of course I did. Sorry for the typo.
Philip.
-tony