N-Channel MOSFETS are more commonly used in electronics but have the
disadvantage of leaving the circuit hot. The switching occurs at the ground
side. This is not a good idea in boats because it leaves the possibility of
stray currents. P-channel MOSFETS switch the supply side so the circuit is
dead when the MOSFET is off. That is why I chose P-channels for my remote
light switch system.

The down side for P-channels is that they can carry less current than N
channels unless you buy more expensive versions like the IRFZ48V and apply a
higher gate voltage than the circuit to turn them on fully.. There are
chips however like the LM1161 that are made to drive P-channel MOSFETS that
add a lot of other features like open circuits and short detection. I am
running LM1161s with a PIC microprocessor linked to the control panels via
RS442 and a portable remote via a pair of Linx 900Mhz transceivers. I can
control the lights, know when the bilge pump is running, when a light is
burned out or a circuit is drawing to much current from the dinghy.

The down side of both P and N MOSFETS is that when they fail they tend to
fail on rather than off so I added individual breakers and 3PST manual
override switches on each circuit to bypass the MOSFETS and operate the
lights.

Glenn

"Sylvain Sirois" wrote in message
...
This one is very hard to ask. I don't understand this concept in French,
so
translating it it's very hard.

I will change all the electricity system in my boat during winter.

A friend of me is an top notch electric engineer and he proposes to make
the
design of my electric system.

He wants to put transistor (MOSFET) to control the different system. It
will
reduce the amount of heavy wiring.

He proposes me 2 different approaches.

One using the channel N. The positive side is directed to the body of the
boat. Like in the Suzuki cars

The other using channel P. The negative side is directed to the body of
the
boat. Like in North American cars.

I don't know if somebody understands what I am trying to explain, if you
do,
which system should adopt for the boat.

What are your recommendations?

Thank you

Sylvain Sirois

http://www.plongeess.com