[Richard L]

Thank for point this important little detail out, it is important for the long-term reliability of the aquamist pump.

The pump should really be turned on and off with the centre wire - disable pump by shorting the the wire to ground.

If the pump was turned on/off via the power wire, it will unsettle the internal electronics and may damage the pump. As you know, all circuit will only work properly at a given steady voltage supply. During the turn-on period, however small, there will be a rise time of the voltage reaching optimal state. The power switch within the pump is unsettled - such as during rapid on/off cycle instructed by an external controller.

Please use a "normally closed" relay (5-pin) to interfce the water pump with your controller.