Electronic – How to make an io pin 12v tolerant

First off if you are controlling a heating element you don't need a snubber.

Second, safe is a relative term. If by safe you are asking if it will explode and catch fire then build it an find out. If by safe you mean can I or anyone here tell you that you have built a safe circuit, meaning that you won't hurt someone.... well good luck getting a commitment there. 240 VAC is generally considered unsafe voltages to mess around with, so its not wise for anyone to give you the go ahead.

Here is a link that shows an application note that will help you design the circuit.

http://www.fairchildsemi.com/an/AN/AN-3003.pdf

Safety advice: One more comment, remember that you need to handle the peak voltage when specifying a part, and handling surges and overvoltage situations that can arise from the power company. So 240 VAC is the RMS value (average), and the peak is times the sqrt of 2, or 340 volts. So make sure you use a triac that can handle 600V for a 240VAC circuit.

Well, the quick answer is no. That won't work.

1) Your flyback diodes are pointing the wrong way, and will always be ON, shorting out the power supply. They are also not rated for 1.2 amps.

2) Your optocouplers, while not a bad idea, cannot possibly handle the current required.

3) It's not at all clear what your logic function is, and I suspect you intended U1,U3,U14,U18 and U22 to be PNPs.

Since you're willing to use external logic, and apparently don't entirely trust your Pi to provide only one output active at a time, I would suggest you go whole hog on logic (it will only take one IC) and do something like

^{simulate this circuit – Schematic created using CircuitLab}

D0 to D2 are 3 bits from the Pi, and they form a binary address of the motor you want on. A code of 1 to 5 will select the motor you want, and 0,6,or 7 will result in no motors on.

I've shown the 5 optocoupler inputs as LEDs, and I've only shown one output. The flyback diode should be rated for 2 amps or more. A 1-amp diode such as a 1N5817 will actually work, but whenever a motor is turned off the current through the diode will briefly exceed 1 amp. This is probably OK, but bad practice. MOSFETs are n-type. Almost anything will do, since voltage rating is less than 20 volts, and current is 1.2 amps.