From: Terence Griffin (terence.griffin_at_nist.gov)
Date: Thu Sep 16 2004 - 13:21:50 PDT
Well, Almost. On the sled these extra contact do not exist.
One end of the thermistor is attached to the charge current
from the Newton, one of the extra contacts. The other end is
attached to two places, 1) the battery pack to charge it and
2) the second extra contact so the Newton can measre the
resistance across the thermistor and give an on screen display
of the charge status.
I'm guessing that the charging circuit is closed by the positive
lead of the battery pack.
Here is a page showing how to modify the sled:
http://dev.newtontalk.net/~dpadilla/battery.htm
I too noticed the lack of the temperature switch shown on the
schematic on Frank Gruendel's page for recelling a battery pack.
I asked Daniel and he thinks its a backup mechanism to prevent
overcharge in case other things fail. He's been using his modifed
sled for year with no problems.
Ok, big question: Can anyone please tell me where I can get a 10k
ohm radial positive thermistor?
- Tere (terence DOT griffin AT nist DOT gov)
Johannes Wolf wrote:
>There is not really the space to install a switch, but the contacts you
>mention:
>one of them is is connected to the (-) terminal of the battery pack and
>the other one is a connection to the built in (in the rechargeable
>pack) temperature sensor (thermistor).
>The Newt decides based on the thermistor readout whether there is a
>rechargeable pack or just alkalines. In case there is no thermistor
>this is just open circuit and therefore the readout is just hitting
>one of its boundaries.
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