Re: [EE] RS232 protection

Hi, Neil:-

My suggestion would be opto-isolation.

RS-232 is supposed to be protected against reasonably high voltages, but 
vehicles can have transients in excess of the standard by 5 or 10:1 and 
EVs have high voltage. Here is one approach. If the baud rate is 
something slow like 9600 there's probably cheaper approaches. Not shown 
is the DC-DC converter module.

AN1992: Isolating RS-232 Interfaces with High-Speed Digital Optocouplers 
<https://www.renesas.com/en/document/apn/an1992-isolating-rs-232-interfaces-high-speed-digital-optocouplers>

Best regards,
Spehro Pefhany


On 2026-02-09 11:45 a.m., Neil wrote:
> Hi all,
>
> I'm reading data from a very expensive device in a vehicle over RS232, 
> using a MAX3232 chip.
> Just reading, so only one data line and +12V/Gnd coming from the 
> vehicle's power outlet.
> Out of an abundance of caution, I would like to do anything extra I 
> can to help protect the expensive device from anything that could go 
> wrong with my add-on. Even shorted wires, etc.
> I did find some (expensive) chips that help with this, specifically 
> ESD, but wondering what other in-between things I can do to just help 
> isolate my device from the one in the vehicle.
> Suggestions welcome.
>
> Cheers,
> -Neil.
>