OpenSprinkler › Forums › Comments, Suggestions, Requests › Can OS/OSPi have remote expansion boards? › Reply To: Can OS/OSPi have remote expansion boards?
Hi again Ray/All-
Since I originally posted the thought of supporting a “remote” expansion board, I have searched through other ways to extend this functionality out into a few locations in the yard, but not coming up with much. I apologize for the length of the post and seemingly mental rambling but I just wanted to convey many of the considerations I’ve made for what I admit is probably not a real broad use-case, but certain would be of interest to some others looking at or already using OS.
My background is as a Network Consulting Architect for a large manufacturer in the IT space; I have a minimal understanding of electronics and somewhat intermediate ability to hack at C, Shell, and Perl coding. My situation is that I live on an acre which has 2 separate 7-conductor runs, one to the front yard and one to the back, so I am limited to 12 zones which is how many I have and all that my Irritrol controller will drive. I want to sub-divide some zones and ultimately increase by quite a few zones (perhaps double what I have) to go with drip irrigation, a misting system, soakers for the foundation, and adding zones to garden beds and to keep compost piles damp, along with also controlling landscape lights, maybe a pond/waterfall pump, etc. I know I’m likely into different voltages and well into scope creep!
I’m ready to pull the trigger on OS or OSPi, now maybe the OS DC, and have been for about 2 years. The cost is not an issue and the capabilities were great when I first found it and only keep improving.
The firm that sold the Irrigander has since gone out of business. That product was still limited in some respects, although not for my purposes, in that it was essentially multiplexing multiple zone wires (with PCM?) over a single signal wire AT the controller with one device. Then, at the valve box, another device would decode the signal to control multiple valves. So, one wire could INDEPENDENTLY control 2/4/8 valves. I had figured that I could possibly expand my reach from 12 wires to control 96 zones.
My challenge is possibly laziness in that I would like to have a common cable for signal and same or another for power looped throughout the yard instead of having to home-run each new, or relocated, zone back to a central controller. I most recently had considered running Cat5e/6 STP cable in conduit along with either 24VAC or 120VAC (US mains) in a parallel conduit to select places in the yard. I was looking at a Kickstarter project called Chainduino, which is an RS485 Arduino board with inline power (not 802.3af/at nor UPoE), thinking about daisy-chaining these coupled with shields to drive solenoids and lighting relays in the yard. What keeps me from pulling that trigger has been skepticism that I could successfully port the Open Sprinkler code over to another Arduino clone board.
When I mentioned commercial “decoder” controllers it was as an example only, not so much that I would like to see OS branch out to support commercially-available decoders. I like the concept since you could treat valves, or even sprinkler heads individually, as addressable objects which could be commanded over a some digital signalling mechanism, but I agree these are all closed and the decoders themselves are fairly pricey at ~100USD per zone (the commercial controllers start in the low 4 figures).
I really don’t like the concept of wireless, unless its strictly WiFi or maybe NRF24L01, since the 315/433/6xx Mhz transmitters/receivers could potentially conflict with other such devices, because wireless is potentially vulnerable to attack, because wired should be more consistently reliable, AND because I need to get power to these devices anyway. I’ve looked at Powerline networking but cannot find any available examples at 24VAC.
Thus far, RS485 or WiFi seems to be (academically) the most robust way to push a packet out onto a ring, star, or daisy-chained bus and have some remote device recognize it has been summoned and take action accordingly, while all others able to hear the same packet just silently disregard it. My perspective is that I look at the work to trench for cabling being something I want to do ONCE and regard it as my BACKBONE which could be tapped into at various points later as I move zones around or add other “things” to control without having to massively re-wire. That said, this only needs modest but RELIABLE throughput to ensure that the solenoids and relays perform accurately, so 2400bps to 200-300kbps is all that would ever be needed.
If you think the 2×4 ribbon from OS to OS Zone Expander could remain reliable over Cat6 cable up to about 300 feet, I may just try that. Then, my ask is if you would consider making the zone expanders in smaller increments like maybe 4/8/16 lines or maybe as stackable like shields onto an Arduino? Also, does each successive Nth expander have to be slung off of the last, or (N-1)th, expander? I really don’t care whether I end up with multiple OS units or a single OS unit with multiple remote expanders, but managing them as a single entity is a MUST. An alternate thought would be an 12~24 VAC/DC version of the OSBee shield, perhaps with LiPo battery, small solar cell, and NRF24L01 or WiFi, where you end up with something like a 4-zone controller completely sulf-sufficient but centrally managed. Dig Corporation and Orbit both make a small battery-powered, four-zone controller but they have all of the features of a 1980s-era off-the-shelf controller, meaning no remote programming nor control, no updates of weather, timezone, nor sunset/sunrise times.
Thanks for listening, Ray/All!!!
@Paul: thanks for bumping the thread back into relevance!
Rob in Prosper, TX