OpenSprinkler Forums Comments, Suggestions, Requests Can OS/OSPi have remote expansion boards?

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    Hello Ray,

    I have been following OpenSprinkler for quite some time and will eventually pull the trigger since it is extensible enough to do better than most commercial controllers, even the “smart” and Internet-enabled variants. My question is if it may be possible to re-work the concept of a central board with relays/triacs/transistors for one where the controller uses a signaling protocol over two/three/four wire already in the yard, so that existing valve wiring may be multiplexed and relays/triacs be installed in a valve box in the ground. Irrigander makes a device which takes in 2/4/8 valve wires at the central timer and uses two wires to the yard, where the remote relays for up to 8 valves may be spread out in the yard but connected to the same two wires. I have a 12-station controller and needs to add and subdivide zones but not real interested in stringing new wire throughout the yard when I should be able to re-purpose existing 7-conductor cables with Irrigander expanders into 1 common and 6 signals actually controlling up to 48 valves instea of only 6.

    Commercial irrigation systems, such as for golf courses, use “two-wire” systems and they are very expensive. I also found that they may be fairly common in residential applications in Europe, but thus far I only found Irrigander as a sort of retrofit from a legacy system with one “zone” per signal wire to one where the same wire may allow differential control of up to 8 valves.

    Is it possible to use Zone Expansion boards up to 200 feet from the OS main board? Or, is it possible to consider separating the switching function from the brains by shimming a resilient signaling mechanism in the middle? I do data networking well and can hack together a script or program if I know the bounds of what’s possible with the hardware, but I thus far only get electronics at a very high level, meaning I understand what the circuit does but wouldn’t know where to begin about choosing different components to better suit a different requirement.

    Any thoughts? Or, am I asking about such an isolated use-case that I’m better suited to leverage both OS and Irrigander expanders off the shelf?



    I’m bumping this old post up because I have a similar need. There may be other threads that cover the concept, so please direct me if you  know of any. I’m not coming up with the right search terms for a better hit. Has anyone come up with a method for controlling more valves that they have wires to drive directly in the valve box? I ditched my old sprinkler controller because it’s limited to 6 zones and I’ve added a couple more, but I also don’t have enough strands of wire in the valve boxes to support the additional zones. I could run the wire, but I’m hoping for a “cleaner” solution. I’m kicking around a couple of ideas for adding zones, but my electronic design knowledge is weak enough that I’m not sure of the feasibility.

    One idea would be to put a small board with a serial to parallel shift register, voltage regulator, and SCRs in the box, and send the power, clock, and serial signals down the existing wiring. I don’t know how feasible this is. Would the attenuation in the sprinkler wire be too high to get a clean clock signal? I don’t know how sensitive shift registers are, or whether there’s a common strategy for cleaning up the clock signal at the remote end of a long run. I’m sure there are other problems with this plan that I’m not anticipating.

    How about a wireless remote controller, such as an Arduino Yun? Or possibly a wired Attiny board that can process a serial signal and break it out to drive the valves with mosfets or SCRs? I’ve got some DigiSpark Digistump boards I bought on a kickstarter I could conceivably use. Have any of you solved a similar problem or know of a non-OSPi project that I could leverage or learn from?
    Thanks in advance,




    First, I apologize for not responding to RobTX’s first post. I must have lost track. I don’t have enough knowledge to comment on commercial 2-wire systems. These systems are closed source so we don’t know the encoding mechanism without some serious reverse engineer efforts. I also suspect different companies use different schemes, so I don’t know how practical it is to add support for these systems.

    Second, I believe it’s possible to use expansion board with a custom extension cable of a couple hundred feet long. I’ve heard some users have done this using a long Ethernet cable.

    Next, we will soon add support for remote sprinkler stations installed on a different OpenSprinkler — say if you have two OpenSprinklers, you can use one as a master controller, and specify stations that physically exist on the second OpenSprinkler. This should be a fairly simple firmware change — as of now the firmware already supports remote RF stations, which allows OpenSprinkler to switch remote power sockets.

    Regarding Paul’s comments: the OpenSprinkler expansion board is already a board that has shift registers and triacs. It’s basically a way to use cascaded shift registers to extend the number of stations. Is this similar to what you described?



    The concept of a remote expansion board would be helpful.



    @Ray; sorry I didn’t respond sooner. I checked back a couple times and didn’t see your post, and I had the “Notify me of follow-up…” checked but never got notification. In any case… yes, despite the fact that I said “SCRs” I meant a shift register and triacs/relays/SSRs. If I can drive a shift register at the end of a 50′ wire run, it should do what I need. I want to keep it small because I don’t ever anticipate putting even 8 valves in a box with the current layout of my irrigation system, but I’ve got a place where there used to be one valve and I’ve grown it to 3.

    I thought I posted another message to this thread, but it’s not here so maybe I got sidetracked and didn’t press “send”. (DOH!) One solution I found since the original post would be to convert the signal I’m sending down the wire to DC, send one polarity down for one valve and the opposite for another valve, and have diodes in series with the valves to get them to respond to the proper voltage. This could be done with a 24VAC relay that would be driven by the OSPi and a rectifier circuit to convert the 24VAC to probably about 12VDC (I’m not sure about the AC-DC voltage conversion to drive the valves). This wouldn’t allow much expansion, but it should work to add a single valve.

    Maybe I’ll throw together a mini version of the expansion board, give it a try, and post my results here… as time permits. If it works okay I’ve got a couple more valve boxes that could use an extra valve to add a zone, but none of them would have more than 4 valves so a full expansion board wouldn’t be practical.



    Basically to handle valves that are very far apart there are two solutions. One is to use a long extension cable to connect the main controller with the expansion board. This is suitable if you have lots of stations wired to the expansion board, allowing you to place the expansion board as close as possible to those valves. The second solution is to keep the expansion board close to the main controller, and use long wires to connect to valves. This is suitable if you just have a small number of valves connected to the expansion board.

    Of course another potential solution is to get a second main controller, and use the upcoming remote station feature to have the first main controller talk to the second one. But this has more added cost.

    There were a couple of requests of developing a remote expansion board with radio frequency chips. I don’t think there is sufficient demand to invest time and money on developing such a remote expansion board. Even if we did, the cost would not be much lower than getting a second main controller.



    I purchased an expansion board hoping that I could use the existing cable from my controller to power it, but found that the cable is only 4 cores and the expansion board requires 8. I cant run a new cable as it is through my house, so I am interested in the slave unit feature mentioned above.
    Is this released yet?



    What type of cable do you have? OpenSprinkler expansion board is shipped with a 2×4 pin cable. If you need to you can make a custom cable as long as it’s wired the same way. Even at the minimum it needs 6 wires, so your existing 4 wire cable is not sufficient.

    I did ponder about the idea of remote expansion boards, but it’s not really cost effective. Because it needs to receive wireless signals and in turn control the shift register, it will need at least a microcontroller so in the end it will not be that much different from just getting a second main controller.



    We are still adding the ability to have remote stations which is what I think you mean by master/slave feature. We expect to have this out in the next version.



    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!!!

    : thanks for bumping the thread back into relevance!

    Rob in Prosper, TX



    @RobTX: I will try to cover your questions as much as possible below:

    – I have from time to time received questions about the 2-wire system (which includes an encoder on the controller side and decoder at each valve). I honestly don’t have much knowledge about how they work, and most commercial products are closed-source so we don’t know what the encoding scheme is (and it may differ from product to product). Therefore this is not a cost-effective solution. As you said, this can significantly increase the per-zone cost. I don’t think the 2-wire system is common in most residential applications, so we don’t know how big the market is. So unfortunately you are asking for a solution that we don’t have.

    – I am reasonably confident that using a Cat6 cable to make an extension cable should work fine for 300 ft. To be sure, you may want to measure the resistance on each wire. As long as the resistance is fairly low, it should be ok.

    – We have no plan to make smaller expansion boards. First of all, they are not going to be much cheaper — a 1 zone expansion board is not going to be 1/16 the price of a 16 zone expansion board. Also, creating multiple versions makes it difficult to predict the demand for each version, so it’s harder to prepare stock. For these reasons we do not plan to create smaller expansion boards.

    – The current design of expansion boards is that they are to be daisey chained. If you have a particular layout on a graph, you can figure out what’s the best way to connect these expansion boards to minimize the total length of the extension cable.

    – We are working on adding support for remote stations in the next firmware. So if you don’t mind having multiple main controllers, this would be a good option, as it will allow you to manage all stations in a central interface, and you don’t have to run long extension cables.

    – The design using OSBee Shield is a possible solution, but you will end up writing a lot of code because the demos for OSBee Shield are all pretty rudimentary. One reason I am not actively working on OSBee and making it into a real product is that I haven’t quite figured out the outdoor waterproof enclosure design. Also, if it is going to have WiFi it will definitely need, as you said, solar cell and rechargeable battery. These involve tricky engineering issues that I am not quite ready to tackle.



    These are all very interesting options. In terms of stringing extenders out from a central unit: Do they have to be daisy-chained, or can they be a hub/star configuration?



    They have to be daisy chained because that’s how the shift registers work.



    I am very interested in using two controllers as one (remote stations). Will this be supported by the DC, AC and RaspPi models? My primary interest is in the DC model as I’d like to power the remote unit with a battery and solar.




    Remote controller feature will be available in the upcoming firmware 2.1.6. Most features of 2.1.6 have been implemented but we are still doing final testing. Remote controller feature allows you to set one or multiple controllers in ‘remote extension mode’, and a master controller can send commands to the remote controllers to turn on/off stations.

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OpenSprinkler Forums Comments, Suggestions, Requests Can OS/OSPi have remote expansion boards?