Hello,
After spending the whole day transferring the layout onto a breadboard (with through-hole traces :-!) using transparent film and numerous colorful markers, I noticed that R13 on the layout doesn't offer any significant resistance because the connection holes on the negative film are connected. This could potentially be corrected to prevent damage to the vehicle or the PC

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Otherwise, I'd just like to say thank you very much! I hope I'll be able to get it working tomorrow, as soon as Uncle Conrad provides the appropriate optocouplers!
Have a good evening!
Toby.