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I'm looking to have several devices attached to a long (total ~10 m) powered i2c bus. The bus would be regulated to 5V at one end and the whole system will operate in exposed outdoor conditions on a balcony (i.e. limited protection from weather exposure and humans/squirrels poking it occasionally). Each individual device on the bus will contain an MCU and a suite of sensors.

This question is specifically about protecting the device ports (power/signal) on the bus from over voltage. Other concerns such as mechanical protection, coating, UV resistance, thermal dissipation in hot summers are out of scope.

I have a reverse polarity protection on the input to each device using a p-ch mosfet (it has already prevented me from frying a couple of micros during testing and development...) but I'm wondering if I should add additional protection on the power/signal lines in the form of a TVS and/or zener. I'm thinking about coupling from nearby lightning strikes/weather/mains and ESD from curious humans and "wildlife" on the balcony (is that a thing?).

Are such protections a reasonable thing to add or am I overestimating the possible damage?

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    \$\begingroup\$ Depending on the length and arrangement, it is possible to pickup tens of thousands of volts just by being outside in the right weather conditions... see this video by Mr. Carlson. \$\endgroup\$
    – rdtsc
    Mar 11, 2020 at 13:55
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    \$\begingroup\$ Protection against squirrels? You are optimistic. \$\endgroup\$
    – user16324
    Mar 11, 2020 at 14:11
  • \$\begingroup\$ @rdtsc interesting, so I'm not crazy... \$\endgroup\$
    – Emily L.
    Mar 11, 2020 at 15:41
  • \$\begingroup\$ @BrianDrummond like I said, mechanical protection is another topic. \$\endgroup\$
    – Emily L.
    Mar 11, 2020 at 15:41

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