The inputs for this module are active low, meaning that the relay is activated when the signal on the input header is low. This is because the indicator LED and the input of the optocoupler are connected in series to the VCCpin on one end, so the other end must be connected to ...
2 If the reference input voltage is likely to exceed VDD by more than 0.3 V (e.g., during power-up) and the reference is capable of supplying 30 mA or more, it is recommended to use a clamping diode between the REFIN pin and VDD pin. The diagram below shows how the diode should ...