OpenSprinkler Forums Hardware Questions OpenSprinkler Pi (OSPi) 3 wire ball valves and multi moisture sensors on the OSPi board

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    my current system has 24V DC ball valves installed, since its battery powered, I have had no “black out” or “brown out” to consider since when I am in under voltage status, the system goes into lock mode closing all open valves long befor it fails to power the cpu. Unfortunatly this system is not “smart” it has no clue as to the real condition, its working of a fixed time table or by manual control while feeling the earth for its moisture, as I usually do.

    I want to make it smart. Online uplink is available and a close by wunderground station too.

    I want to replace it with OSPi

    Question: Is the OSPi board able to handle 3 wire ball valves. This means one wire goes to – and the other 2 wires are + for open and + for close. The valve stopes when reaching full open or full close position by itself. (those valves have a low energy consuption, as a solenoid valve uses energy as long as its open, and my system is solar power feed and the pump supplys 15L/min that means long watering times, that means the consumption for the valves are a sizable amount of the total consumption including controler and pump….)

    If not, what do I need to order additionally?

    Also, I currently have several different zones and they are fairly individual, some are under trees and dont see much rain, other are in bright sunshine and dry up fast others have just a foot by foot wide soil between concrete and sidewalk. So I want moisture sensores for each zone.

    How many sensores does the OSPi handle?
    If one, as I did understand it, how do I expand the availabe inputs?




    It’s tricky, if not impossible, to modify OSPi to interface with 3-wire motorized ball valves. The first reason is that OSPi runs on AC power, while this valve requires DC power. OpenSprinkler 3.0 DC-powered would be able to interface with this valve, but even so, a hardware modification is needed: OpenSprinkler uses common anode (positive) design, while this valve requires common cathode (negative). Basically, the valve needs the common wire to be ground, while the controller has common wire dedicated to positive. As a result, you will need a transistor adapter to invert the logic of each zone. I’ve actually designed this transistor adapter (basically made of a PNP transistor on each zone) for another customer, and I’ve tested it to work well with 3-wire ball valve. The way it works is that each motorized ball valve will take over 2 zones, one for opening, one for closing. Let’s say the valve take 10 seconds to open (or close), so you have a program that does 10 seconds on the ‘open’ zone, that will open the valve at the designated time. Similarly for the ‘close’ zone.

    So in short, it’s difficult to modify OSPi to interface with this valve. OS 3.0 DC-powered can, and it requires an adapter to do logic inversion, and I do have that adapter as well.

    Do not that among the different types of motorized ball valves, there is a ‘2-wire auto return’ type, which would be the easiest to work with OSPi or OS, as it would not require either hardware or software modification.



    Hi, Ray

    thank you for your feedback.

    Since you dont talk about the sensor input, I suspect I got it right with 1 sensor.

    And so I have come up with a circuit idea.

    I will use the output of the pi to switch between the zones.

    So I activate zone 1, thereby I switch a relay that conects the sensor of zone 1 to sensor input. And I activate a time unit.

    If the zone is wet, then zone 1 is switched off again before time unit activates the ball valve.

    If the zone is dry, then zone 1 is kept on, and the time unit after a minute or what ever will aktivate a switcher relay that in turn will activate the ball valve. then after a fixed time (modifyed by weather data) the zone 1 is going offline, the senser goes off line and the switcher relay will switch the ball valve back. then later on the moisture level will be checked again with the same procedure. and if still to dry, watering will ocure by the same parameters as before.

    I want do this for all my zones.

    Question, would this work?

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OpenSprinkler Forums Hardware Questions OpenSprinkler Pi (OSPi) 3 wire ball valves and multi moisture sensors on the OSPi board