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List:       newtontalk
Subject:    Re: [NTLK] Power Adapter Developer's Guide
From:       Jake Bordens <jake () allaboutjake ! com>
Date:       2018-04-15 19:10:29
Message-ID: 705F69AA-7207-4A38-923C-7D4AB69E3847 () allaboutjake ! com
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> Cool. I am quite unsure if there is any provision to protect the batteries. I read \
> the documentation and  understood that the pin directly connects to the power \
> system, no fuses or anything. So the question is,  is there charging electronics \
> between the 7V line and the battery, or instead between the power pin and  the \
> battery. Not sure how, but it should be possible to measure if there is a mosfet or \
> any such thing  between the battery and the internal connector.

This is my concern.  "Unfused" makes you think it is a direct connection between the \
battery terminal and the "unfusedVin" pins on the internal connector. Checking with \
my meter, you don't get direct continuity, though you do get a short beep which \
usually indicates there are some capacitors between the battery terminal and the \
"unfusedVin" pins.  Perhaps there are mosfets in between..  I ordered some connectors \
so that I can build a voltage/current monitor and put it between the OEM power supply \
and the Newton to see how it behaves during charging.  Then I can compare the \
behavior of the internal port.

For the internal charger, my current circuit involves two diodes and the 1k resistor. \
Really you need only one diode to prevent the battery voltage from triggering the \
sense pin. (I did verify that a 1k resistor between sense and unfusedVin while on \
battery does make the newton think there is an adapter installed, so a diode is \
necessary)  However, I'm using 2 diodes as to keep the voltage drop somewhat the same \
between the sense pin and the batteryVin pin.  I'm not sure what the Newton uses the \
voltage on the sense pin for, but the docs indicate it should be the same as the \
battery voltage.

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