On Tuesday 22 January 2002 09:58 am, you wrote:
> Hi folks,
>
> I'm answering a couple of mails at the same time here to
> save some bandwidth.
>
> c) The resistor behaves like a temperature dependant
> potentiometer. The resistance
> changes with the temperature, the amount of change
> tells the Newton the change in temperature.
It was my impression that this is the thermistor. An
NTC_at_10k-ohm @25c varies resistance nicely with temperature.
I have performed the AA-cells "hack" and used a non-axial
thermistor of this type; I can open the battery status pane
of Avi's backdrop and watch the battery temperature vary
as charge progresses.
I used non-axial because it's more "plump" and with my
positioning, it is always in physical contact with two
cells as long as there are batteries in the tray.
> You do not need the thermistor. The Newton will charge
> just fine without it. As long as nothing goes wrong, you
> are safe. But only as long as that.
This sounds like some kind of fuse, rather than a
thermistor. I don't have anything of this sort in the
conversion. I don't worry about it too much -- there are
many other horrible things that can (and probably will)
happen to a Newt first -- broken screen, jaggies and carpet
static (which already bit me once) being at the top of the
list!
> Keep in mind that the battery tray lacks the negative
> power supply terminal, if my memory doesn't plays tricks
> on me, there's just a
> hole in the battery holder and the spring contacts the
> battery directly.
> This
> is where you would have to connect the resistor to.
I have a "floating" metal plate for a negative terminal
right there, connected by a lead to one side of the
thermistor, I believe. It works fine -- battery contacts
the "nub" on one side of the plate (which I just fabricated
from some old battery cage parts from a walkman) and the
Newt's internal spring contacts the other side of the
plate. The lead is short and fairly stiff, so it stays in
place nicely, but has enough play to make contact with both
surfaces.
> I'm sure this setup works just fine. However, considering
> the fact that 2x00
> machines don't exactly grow on trees anymore, it doesn't
> quite match my personal
> quality standards ;-))
Well, for just a moment, they do grow on trees it seems! ;)
Seriously, though, this setup does work great with my 9w
power adapter and I even have at least two perfectly good
original NiMH battery packs that hold a charge... But a set
of modern high-capacity NiMH cells works a *lot* longer on
a charge, so I prefer to used the "hacked" battery cage
instead.
-Aron
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