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You can control a lot of different lights, water valves, and ventilation systems with relays like this. With some sensors and your Software Sketch ideas, an intelligent system may be born. NOTE: Sometimes switching these kinds of loads can cause Electromagnetic Interference, Arduino lockup etc. More information on handling these problems is available HERE:
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Sometime, when controlling lights and other loads such as motors, pumps, Solenoids etc., problems occur. Problems may include:
Lockup of the Arduino controlling the relays and switching
Loss of ability to communicate with a PC connected to the Arduino by USB
Noise and erroneous readings on sensors or attached devices when relays or loads are switched
ma non era optoisolata?
Giacomo