How much current and how long a pulse is required to open and close the Ehcotech 4.5-9V 1/2″ Magnetically Latching Solenoid Valve? And does it require continuous current to stay open or closed?
The coil resistance is about 10 to 13 ohms so you can draw between 450 mA and 900 mA depending on your voltage. That said you should only have to turn it on very briefly (for a fraction of a second) in either direction seeing as it is a latching device. Once latched no current is required until you need to change the setting again.
When changing from open to close you simply need to change the polarity of current and enable current flow briefly (like 1/4 to 1/2 second). This is ideally accomplished using a micro-controller and an H-Bridge since you will need to change polarity, and have control over duration of the pulse.
The usual spec for such valve is 50 ms to change state. so I would use a pulse of about 0.1 second (100 milliseconds) to control it. you can use a SPDT relay to control the direction or a full H-bridge controlled by an arduino or similar MPU. an H-bridge will need 4 darlington or better 4 MOSFET.
very easy to do.