Protection for ports of microcontroller with long wires connected to them?

[grizedale]

Hello,

We have two separate microcontroller circuits (each on its own PCB), which are at either end of a lorry and are powered by the lorry battery.

The microcontrollers have a connection from port of one to port of the other by a 4 metre piece of wire.

Do you think that the following (which represents the two microcontroller ports A & B and the wire between them) will give enough protection to each of the microcontroller ports?............ie protection from electrical disturbances which may couple into the long wire and damage the microcontrollers?

https://i46.tinypic.com/5vx0qr.jpg

 

[TuAtAu]

i suggest put a 5V zener diode parallel with C4? It gives over-voltage protection.

 

[grizedale]

Thanks, -how bad is this problem of overvoltages getting coupled into long wires?

-I know its well talked about, but who really believes it actually happens?

-are we saying that if i didnt put the zener there, and i scope across the capacitor C4, that i am going to see wildly high voltages all the time?.....i somehow dont think so?

A voltage across a capacitor is energy....so where is all this energy coming from?

...i suppose the long wire is like an antenna, but to get a decent antenna means having good matching etc etc...things that are not prevalent in our circuit, so surely all this talk of overvoltages getting coupled into long wires is just nonsense?

 

[TuAtAu]

Thanks, -how bad is this problem of overvoltages getting coupled into long wires?

-I know its well talked about, but who really believes it actually happens?

-are we saying that if i didnt put the zener there, and i scope across the capacitor C4, that i am going to see wildly high voltages all the time?.....i somehow dont think so?

A voltage across a capacitor is energy....so where is all this energy coming from?

...i suppose the long wire is like an antenna, but to get a decent antenna means having good matching etc etc...things that are not prevalent in our circuit, so surely all this talk of overvoltages getting coupled into long wires is just nonsense?

you got your point. If V2 and V6 is stable all the time, then it should be no problem at all you won't see high voltage all the time, just incase, somehow your V2 and V6 is larger due to some unexpected reason, at least the diode can protect it. orelse, it should be a good circuit without zener diode too. So far I cant see any other things that will harm your uC currently.