Jaume Aragay Badia wrote:
> 
> Do you think MOSFETs or FETs would be a better solution to get noise
> inmunity?

I assume you mean MOSFETS and JFETS.

Neither. FETS use a voltage to switch, so it would 
actually be less noise resistant than a good old 
BJ transistor that uses current.

It seems like you need some extra decoupling on your 
PCB. Connect 4 or 5 100nF caps between VDD and Vss all 
over the PCB.

You could also do with some common mode choking on the 
contact lines. Wind a choke toroid with the 45V lines.
Start at the same point. Wind the wires in the same 
direction through the hole, but one to the left and 
the other to the right. Put on as many windings as 
you can.

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