Large OpenSprinkler Pi System

[lordryst]

I am working on a large project as part of a group to distribute water to several hundred locations in about a 500m radius. We are looking at your system, and like what we see, but we have a few questions.

1. Can you split the extender lines, so as to connect 2 extenders, in parallel? It appears that you use I2C as your communication protocol, but I didn’t see a means of addressing, so we can’t tell for sure. This isn’t as crucial, but would be nice.

2. How far can you chain extenders? By modifying the firmware we can have many extenders, and in another question it was stated that an extender could be about 50ft from the base station, but can another extender be another 50ft? This element is crucial for us, as we cannot run long lines to solenoids.

If this works out, we will probably ask more questions as we develop a central system for controlling multiple Open Sprinkler Pi systems on a mesh wifi network. We would be happy to share our findings with the community.

[Ray]

1. Can you split the extender lines, so as to connect 2 extenders, in parallel? It appears that you use I2C as your communication protocol, but I didn’t see a means of addressing, so we can’t tell for sure. This isn’t as crucial, but would be nice.

I’ve never thought about it, but now you asked it, I think it’s fine to connect two expansion boards in parallel. It’s simple shift register cascading, so no I2C communication. Keep in mind that this means the two expansion boards will always be synchronized — always outputs the same.

2. How far can you chain extenders? By modifying the firmware we can have many extenders, and in another question it was stated that an extender could be about 50ft from the base station, but can another extender be another 50ft? This element is crucial for us, as we cannot run long lines to solenoids.

This is a commonly asked questions. Frankly I haven’t done careful study about it. The issue is that because the extension cable carries straightforward logic signals, it’s prone to interference if you run it over a very long distance. The software does refresh every second, so if the signal gets interfered at one moment it shouldn’t persist. So it’s probably fine to chain several expansion boards over 50 ft each.

[Biojardim]

Hi,

Im working in big project too. My goal is to have an OSPi and 11 extension boards. Each extension board is 50 m from each other, with an distance of 550 m

I allready tested at the midle of the distance and i noticed that i have signal to extension boards but is not enought to turn on the valves.

With the FTP cable that i use to connect each extension board i use 2.5 mm power cable for 24V AC.

This power came from the same power supply.

So if i connect the 3x GND from FTP cable to GND at 2.5 mm power cable (24V AC), in this way the valves work fine. Tested with 1x extension board at 300 m from OSPi.

But now i having some trouble, when i try to connect the 5x extension board there is no answer from OSPi.

My question: using the interval program is there any limitation of extension boards? We need to change the code?

Br
Claudio

[Ray]

Dan is probably the best person to ask about this, but I assume the interval_program limits the number of stations to 32. It should be easy to increase this number to anything, I am just not sure if it’s a matter of changing one macro define, or there are multiple places that need to be changed.

Regarding your wiring experiment, I think it’s important to keep the resistance of the wires low — it helps to use thicker wires, or combine multiple wires as you did.

[Author]

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