Relays

[QMESAR]

Thank you davidcoton,

Your post makes 100% sense and I fully agree with you

a resistor (highest possible value consistent with delivering enough current in normal use) should be enough protection.)

and this make total and absolute sense and for sure the better option ,

Using an optoisolator (especially to drive a local relay which itself provides isolation) is definitely "belt and braces".

Kind Regards

[gordon77]

The advantage of adding the opto interface as shown by pcmanbob is that it will interface with the pi, a lot of commercial relayboards are not designed for the Pi, usually the Arduino, and may not switch reliably with 3.3v.

[pcmanbob]

Using an optoisolator (especially to drive a local relay which itself provides isolation) is definitely "belt and braces".

But in this case the relay is not providing any isolation between the 12v and the pi gpio because the relay its self is driven from the same 12 supply it is only acting as a heavy duty switch for the current required by the valve.

so extra isolation is required between the GPIO and the relay board, hence suggestion of opto-isolator.

[QMESAR]

Thank you to all for the valuable discussion
I have learned some very important things

Kind Regards
QMESAR