I have been looking for a long time for a way to get dry contacts (also called potential free) with NO (Normally Open) and NC (Normally Closed) outputs, as SONOFF 4CH modules (Pro or Standard version) do excellently.
This type of dry contact equipment is extremely versatile. It allows the control of electrical appliances or lamps, but also watering valves regardless of their supply voltage (12V, 24V, 230V …), or to send a short pulse to open an automatic gate, actuate an electric waste or trigger a siren. The dry contact works without injecting any voltage specific to the module, it only connects or disconnects two wires according to the NO/NC state, which avoids any risk of electrical conflict between the module and the controlled device.
I ordered this Zigbee module to test it. These tests are not sponsored: I bought this product with my own money, sometimes recovered through resales such as those available in my garage sale.
The documentation indicates that the voltage supported on dry contacts can be up to 240V maximum, with a capacity of 10 A (i.e. 2200 W at 220 V for a resistive load such as a radiator). For inductive or capacitive loads such as LEDs, the limit is 220 W maximum at 220 V, because these loads generate peaks of current at start-up that could damage the relay if the power is too high.
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