I am thinking of something like this. The mosfet (not sure if that particular one is the best election, maybe overkill for the task) turns on/off the booster and the H-Bridge, the MCU waits till the capacitor is full and dumps the load in one polarity or the opposite.

 

Going back to the first post, it seems that the goal is to remotely control the valve via radio signals, from a fair distance. So really there are questions that need answers before any suggestions make sense. First, in the original system, what decides if the valve is to be switched on or off? Time of day, moisture sensed in the ground, or what?
Next, what sort of longer range do you want for the remote control? Several meters, or several miles? My thinking is that duplicating the control signal from the sensor circuit is by far the simplest approach, and that will not require any arduino modules at all.

 

The original design is just a very simple water timer like the one in the picture , it opens the valve at preprogrammed intervals of time, just that. I'm only interested on the mechanical design, (the plastic case, battery holder and the solenoid inside) I want to replace the pcb inside with a custom design that includes a Lora modem to remotely operate the valve based on a fairly complex centralized set of rules that will change over time.

The plan is to have a network of about 5 to 10 valves (each valve with it own ID). Every valve will wake up every 10 minutes and ask the master if it should be open or closed, perform the action if it's different than it's current state and go to sleep for the next 10 minutes. The distance between valves and master is up to 200 meters (without direct sight)

 

I think that if the valve package is going to transmit based on a time interval that it would make more sense for each valve to announce it's condition, open or closed, and then receive an instruction to either open or close. Of course there is a big difference between knowing which position a valve is in versus just remembering what the last command was. And knowing if the downstream pressure was high or low could deliver some clue as to if that area was being irrigated or not. That information could be valuable.

 

And knowing if the downstream pressure was high or low could deliver some clue as to if that area was being irrigated or not. That information could be valuable.

I agree, I already thought about adding a flow sensor to know not only if the area was being irrigated or not but also to detect leaks or know how much water has really being used, I would absolutely implement such feature if I was designing the device from scratch but I want to use what I have, the enclosure is well designed, waterproof , elegant, compact.. I don't want to modify it or add external sensors with wires etc.. I want to try to make it work with the bare minimal stuff. I may design a 3d printer version in the future and add more features but I need to make the solenoid open and close in the first place