Opto-isolator circuit for Arduino?

Hi

Does anyone have a circuit or must-do's for an opto-isolator circuit for an Arduino. I want to connect three long wires, from weather instruments, to my Arduino. We have a lot of lightning storms in our area so I must protect the Arduino and GSM module from EMF Spikes.

Any ideas, circuits, suggestions?

Best regards

Andre

Maybe add zener diodes in parallel with LED as well.

Use an appropriate Transorb or a Varistor from each conductor to earth ground. http://en.wikipedia.org/wiki/Transient-voltage-suppression_diode http://en.wikipedia.org/wiki/Varistor

EDIT: Do some research on "surge withstand capability" "SWC"

A small opto isolator isn't going to save you from lightning. It should protect from all the pickup induced on the wires, but provide a good earthing stake outside the building directly bonded to the wire.

Lightning jumps many feet at a time (stepped leader), you have to provide a solid alternate route to ground for the current and perhaps a metre or more of isolation to have a chance against a direct hit to the cabling: Using a length of optical fibre / lightpipe to isolate, bright LED at one end, good photo transistor at the other (you can get black plastic coated light pipe to keep ambient light out) - its like an opto-isolator but can be several metres long.

I suspect someone has already investigated such a lightning-proof opto-isolation set-up before, google around maybe?

Do your three long wires carry analog or digital signals ?