safety
I shorted by accident a circuit creating large voltage to my computer, luckily MBA has some sort of shorting protections — yet this kind of thing should not happen. I would like to have a fuse between my microprocessor and my computer.
What are this kind of protection mechanisms called? USB fuse did not return anything in eBay so I am thinking I am trying to find things with wrong word.
In a nutshell, you want to treat the Arduino and all other electronic components as you would treat a line voltage electrical system. You want to have a weather-resistant case for the Arduino with as few access ports as possible, and you may want to go so far as to plug those access ports with silicone once you have the required wires in place. The easiest way to protect it from the actual watering system is simply to have the electronics at a higher elevation than the water source, while observing all the previous precautions I mentioned.
If you're working with that sort of stuff and anticipate trouble you may wish to get chemical rated safety glasses eg. ANSI Z87.1–2010 with D3 splash protection. These have side shields as well.
In some cases (very high power circuits) full face shield protection (or arc flash suits) may be called for.
This would be somewhat of an extreme precaution for wiring up a typical solderless breadboard with 555s. It's impossible for us to really tell what your situation is.
Unanticipated venting and explosions are very rare occurrences in most conditions. If you're working with (say) 5V DC circuits, it is exceedingly unlikely anything potentially harmful would happen unless you're doing something really silly like peering at a reversed capacitor from inches away.
Best Answer
You're looking for a resettable fuse, PTC, or thermistor.
They're basically a resistor with low resistance in normal conditions, but as they heat up, the resistance goes up significantly. This causes a massive voltage drop, stopping the short circuit (until it cools down again). Since it has some resistance, some electricity is burned off, heating the PTC a little bit. As you increase the current, it will heat up more until it trips.