Re: Voltage Protection

In article <1145380214.667544.53750@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, joost.jager@xxxxxxxxx wrote:
Hi all,

I'm currently working on a PIC circuit to manage the power system in my
sailing boat. Relevant sensory inputs of the PIC are:

- battery voltage measured via a voltage divider (2 resistors)
- current measured via a heavy shunt resistor and a MAX 472 chip

These sensors are directly connected to powerlines. On these powerlines
there is a engine alternator and a wind generator. I don't know this
for sure, but these generators might generate voltage spikes. Maybe the
spikes are absorbed by the battery, maybe not. To be safe, I would like
to protect the inputs in some way, but without losing accuracy.

Does someone know whether or not this is necessary and if yes, how to
do it?

Related to this is: where to put fuses? There are a quite some sensor
lines running to the positive power lines. It does not seem practical
to me to put a fuse in every line. Especially for the current sensor
the extra resistance of the fuses would disturb the measurement. Would
it be an option to fuse the complete system on ground? The risk then is
that the hull of the ship is also connected to ground, so an unfused
short circuit on the battery is still possible.

I was thinking of a DC/DC converter for the PIC for isolation and regulation.
Fuses shouls be near batteries or power sources.

greg
.

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