Hi, thanks for all your replies. Your are right, i'll read more about mosfet choice.
anyway i think i choosen the wrong post title or maybe i miswrite the question.
i know the mosfet IRF520 may not be the best choice in terms of quality etc.
but i think my problem actually is not on the best mosfet to choice, but a problem of wiring circuit.
I think it is a circuit problem that is not strictly related to a specific mosfet but a problem of circuitry.
Let's suppose for a moment that we have ideal digital n-mosfet and that we could imagine those as little remote digital interruptor.
i have to leave the +24V signal pass into 3 wires, A B C, that have a common GND (cable of 4 wires). max wire consumption is 10mA for each.
(ignore for a moment missing resistor that could damage arduino, i say let's ignore for a moment the arduino existance).
I'm trying to connect this 3 wires to the 3 IRF520 modules as for my previous schema of the module.
+24V to VIN of each module
A-B-C to V+ of each module
GND of the 4-wires-CABLE to V- of each module
and indipendent +5V signal to each SIG pin of each module
GND to GND-pin near SIG of each module
What it happens now (tested on circuit with LEDs): [*** THIS IS MY PROBLEM ***]
when i activate +5V Signal to module of PIN A, also B and C have a +24V between V+ and V- .
I want to pilot each signal indipendently from the other.
WHY this happens? (i think) it's because A B C are directly connected to +24V (see the V+ of the module) and when N-Mosfet of Module-A conducts, it is giving the pass to GND for all other Modules (because the GND of 4-wires cable is common to all A B C).
So this is a WIRING/Schema/Circuit problem that i would have also with normal switch push-buttons. is not related to specific mosfet.
What i'm asking to you?
Is there a way to connect the module (or any optimum n-MOSFET) in a way that i could control each PIN indipendently?
To put SIMPLIER and to not disguise who want to try help me,
here is what i want to obtain.
Tha AIM is replace P1 P2 and P3 with a N-MOSFET activated by indipendent signal of +5V
Hope the problem is much clearer now and that someone could help me.
Anyway thanks for your appreciated suggestions and resources on MOSFET world.