This isn’t strictly a Particle or Photon question, but related to other threads on this forum. I’m building an irrigation system for four tomato plants in flower pots. Based on advice on this forum, I am attempting to use a latching solenoid valve to reduce power consumption, with an eye toward making it solar powered. I am using this valve with four outputs so I can independently control the output to each plant.
It is my understanding that for this latching valve, I need to provide a 12V pulse of 30 ms (or greater) duration in one direction to open the valve, and in the other direction to close it. My circuit consisting of a Photon, some digital inverters, and some L293D motor drivers successfully provides the correct pulses. The problem is that when testing, the valve never opens. I can hear a little thud as it tries to open and again when it tries to close, but it does not actually open.
I know that this valve needs water pressure to hold itself open. According to the valve data it works with a pressure of 0.02 - 0.8 MPa. This pump claims a lift of 300 cm, which if I am not mistaken equates to 0.029 MPa, so it should be sufficient (though I have not actually tried to verify a 3 meter lift). The valve calls for a minimum current of 300 mA, and I am using a 2A power supply to power the valve and electronics (using this Pololu voltage regulator for the electronics).
The circuit is working as I expect, based on the oscilloscope images showing an opening pulse and a closing pulse. Is there anything else I need to do to successfully operate a latching solenoid valve?