New and looking for guidance on commercial farm application

[workingtheory]

Hi,

Thanks to everyone for the work you’re putting into this system and support for those of us coming in with limited knowledge in this realm.

I am a vegetable grower in Oregon, and I am hoping to use OpenSprinkler to improve the irrigation on my farm. I’d like to begin with managing seven acres of row crops (mostly on drip lines and a few sections of overhead microsprinkler lines). I currently have a 10hp 220v electric pump moving surface water through 4″ main line and then 1.5″ PVC headers into drip tape. I have approximately 24 manual 1.5″ valves that control sections of fields for irrigation. In order to start irrigating, I currently open the appropriate valves, walk down to the creek and turn on the pump (which has both on/off and an analog dial timer). Later in the day, I can repeat that process to irrigate other sections of the fields.

Needless to say, this is wildly inefficient and in need of an upgrade. Here’s what I understand based on my reading so far – please feel free to correct me if I am wrong:
-I can replace manual 1.5″ valves with electronic valves with little impact on pressure of flow. They are all off of the mainline, so there would never be multiple reduced spots in line. The 1″ valves seem to be a LOT cheaper than the 1.5″ (if I can find those at all).
-I will have more than enough space for all of the valves if I use the OpenSprinkler and expansion board(s)
-I believe I understand how to wire in the multi-strand wires (common wire daisy-chained from the controller and to each of the valves with separate trigger wires hitting each of the valves independently). Does that sound right?
-The farthest valves from the controller location are about 500′. I believe the lines are rated for that distance, right?

Questions:
-Am I missing anything?
-Should I choose AC or DC valves and controller? I’ve read the documentation and FAQ, but I am still a bit unclear. There is power at the controller and at the pump, but not in between.
-Can I run pump start relay to remotely start and stop the pump? How does it communicate with the controller (it’s about 700′ away)? I’ve attached a photo of my pump switch (located at the power pole at the creek). The analog timer is obvious. The other switches are “On-Off-Hand” and “Start”
-Is there anything else I should consider when choosing valves? I know dripworks sells 1″ AC valves with commercial pricing for $13-$19 each.

Thanks in advance for your guidance! Please let me know if anything is unclear or if you have other questions/thoughts.

[ShawnHarte]

For the distances you should use ac equipment. Pushing low voltage dc over those distances would require pretty large wire. For ac the standard multistrand sprinkler wire will work fine. The pump can be wired just like a valve with a starting relay near the pump end. In opensprinkler set it as a master. It will then start the pump when tha valves open. You can set positive or negative timing delays for the master to make sure you don’t air lock the pump or valves.

1″ valves are pretty good for drip lines, beyond that size the price will take a large jump upwards because they are not the “common” type used.

Make sure the pump relay can use an ac signal to trigger, if it can’t full wave rectifers are cheap and common, just add one right at the relay.

Other than that it seems like you have the idea and hardware in place to run just fine with OS. You will need expansion boards to run 24 zones, and the master(pump) will use a zone, just keep that in mind when purchasing.

[Ray]

While it’s common wisdom that higher voltage is better for transmitting over long distance, it’s important to understand the principle behind it. What happens is that when transmitting electricity over long distance, a considerable amount of power is dissipated as heat on the wires. Assuming wire resistance is fixed, the power waste has a quadratic relationship to the current running through the wire (P = I^2 * R). So to transmit the same amount of power over the wire, it’s better to use higher voltage, because the power being equal, higher voltage means lowers current, hence lower power waste.

However, if you follow the logic above, it’s easy to see that if the current running through the wire is the same, the power waste is the same. OpenSprinkler AC and DC are both designed to supply roughly the same amount of current to the valve, hence the power waste would be about the same. Why does OpenSprinkler AC runs on 24V AC, which is much higher, while the DC version runs only on 9VDC? That’s because solenoids are naturally big inductors, and inductors present significant reactance under AC current. So even though 24VAC is almost 3 times higher, that induces roughly the same amount of current compared to powering the valve using 9VDC. As a result, you don’t need thicker wires when using OpenSprinkler DC.

Long story short, to answer your questions:

-Should I choose AC or DC valves and controller? I’ve read the documentation and FAQ, but I am still a bit unclear. There is power at the controller and at the pump, but not in between.

A: either is OK. Note that OpenSprinkler DC is actually more flexible because it can work with both 24VAC valves as well as 12VDC valves. So it gives more flexibility. Common sprinkler valves are mostly 24VAC.

-Can I run pump start relay to remotely start and stop the pump? How does it communicate with the controller (it’s about 700′ away)? I’ve attached a photo of my pump switch (located at the power pole at the creek). The analog timer is obvious. The other switches are “On-Off-Hand” and “Start”

A: a pump start relay is basically a relay that plugs into the sprinkler controller on one side (think of it as a sprinkler station), and on the other wise it connects to high voltage pumps. So when turning on that station, it turns on the water pump. Your photo didn’t attach correctly (seems too big). If you can resize it to a smaller size it should work. Or you can send it in a email to [email protected].

[Author]

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