pin DI0 Low when XBee is broken


I used the pin DI0 to control a 2N39004.

The XBee is 868 Pro (EOL).

If there is a fault in the voltage regulator, the XBee reaches 12V, so the XBee dies.

But that does not end my problem, because the above I can solve with a protection for overvoltage, up to 3.6V. (Zener, Polyfuse or similar).

The major problem to me is that when XBee is broken permit the current flow and allows to pass the current and therefore passes the current through the 2N39004 and switches the cables connected to the relay. In short, DI0 always stays High.

It’s possible to do something for if the XBee is broken, the DI0 pin is always Low.

Best regards,

I am not aware of a way.

Thanks mvut.

Finally I did the following:

1- The first, I added a crowbar protection. Now if dc-dc buck converter fails, as most 3V6 can happen.
2- I reversed the wires in the relay and the output logic in XBee.

Now, the wires are in common pole and NC (normally closed), the jet ski is lock always, when insert the lanyard (contact key in accesories bus of the a car, in this case of the a jet ski) the XBee unlock the started system.

So, if the XBee is broken it will never stop the motor.

But now another problem appears, if anything fails on the voltage regulator or if the relay fails, it will go to NC pole, so it will stop the motor. In the end I still have the same problem.

Ideally, the XBee pin will be Low if the XBee fails. So if there is any failure in the system in general it would not affect what is connected to it.

Sorry for my english.

Best regards,