Ok to hardwire 7 zones (7 x 24V AC valves in parallel) with OSPI?

[nachtigall]

I would like to parallelize 7 zones. These are all Rain Bird XFD2333 Driplines with only about 7 liters per meter per hour. So it takes forever until they have finished (while I have a loud water pump with 800W/h electricity). Due to the lack of being able to to this in the OSPI firmware, I want to do it the hardware way. That is, insert the 7 zone wires into the same port, and those 7 zones will always turn on or off together (they are parallel).

At https://opensprinkler.com/forums/topic/2-stations-at-one-time/#post-76272 I read:

> Also, I’ve seen quite a few customers who want to run more than 10 zones at the same time. I would absolutely NOT recommend doing this. The controller is NOT designed to run a lot of zones in parallel. It’s not a software issue, it’s more of a hardware limitation. The power adapter needs to withstand a huge amount of impulse current to open that many zones simultaneously. Also, the circuit cannot withstand that much current either. So while I understand there is such need, I wouldn’t go crazy on having too many zones open at the same time. If you really need to do that, you should use an external relay, which can withstand a huge amount of current.

I have an OSPI with this power adapter: https://opensprinklershop.de/product/netzteil-24vac-15a-36va/

The 7 valves are all 100-HV-MM Rain-Bird 24V AC. See https://www.wasserundgruen.de/Magnetventil-100-HV-MM-Rain-Bird-Aussengewinde-24V-AC-Serie–HV-Typ–100-HV-MM-Rain-Bird.html

So will this work or will this destroy either the OSPI or the valves or I do not know? (I am not particularly strong in electronics, that is I have no clue really).

PS I know that there is a “group” feature in the recent OSPI firmware. However, I also have about 20 other zones (sprinklers/Hunter MP-Rotator) that cannot run in parallel. I explored the grouping feature but it seems to be to “simpistic” for my use case.

[Ray]

I am not sure what you mean by “Due to the lack of being able to to this in the OSPI firmware,” — if you assign a zone to the parallel group, it can run at the same time with any other zone. So if you assign all 7 zones to the Parallel group, they can all run at the same time. Again, I would not recommend running this many zones together, so you will have to do it at your own risk (we’ve never tested running this many zones at the same time over long period of time). If your power adapter can supply this much current, it should be ok.

[nachtigall]

> I am not sure what you mean by “Due to the lack of being able to to this in the OSPI firmware,” — if you assign a zone to the parallel group, it can run at the same time with any other zone. So if you assign all 7 zones to the Parallel group, they can all run at the same time

I think we already discussed this in another thread some time ago (EDIT: found it: https://opensprinkler.com/forums/topic/parallel-grouping-of-stations-with-2-2-0-ospi-firmware/) . The problem is that I have many other zones (sprinklers not driplines). And I need to always run the sprinkler zones not in parallel with anything else (not enough water otherwise). So, ideally I would need/wish to have a group zone where all its group valves run in parallel, but at the same time this group must be sequential with regards to all other groups/zones.

For example I want to schedule the Group of 7 to run first (all paralell), then afterwards a Group of 2 very long driplines (again all parallel), then a sprinkler zone etc. – these 3 things should run one after another.

That does not seem to be possible. So the only way I can think of is hardwiring unfortunately.

[Ray]

Well you can always write a script yourself and send command to OpenSprinkler to open zones in any pattern you’d like. A single firmware is not going to fit everyone’s need. The reason we make the whole product open-source is to give users the freedom of modify the software in any way they want.

Also, the firmware supports up to 40 programs, so technically you can create many programs to define when does each group of zones start. So in theory you can use multiple programs to do anything you want. It is certainly tedious and difficult to update this group of programs, but it should be able to achieve what you need.

If you want to hardwire multiple zones to the same port, please note that a single port can support no more than 2 parallel solenoids. Each solenoid draws 250 to 300mA holding current, and 500 to 700mA impulse current. The triac on each zone cannot drive more than 800mA to 1Amp max, so it can’t do more than 2 zones. You can always use an external relay, which can drive amps or even tens of amps. That way one single zone switches the relay, and the relay in turn switches high current load.

[nachtigall]

> Well you can always write a script yourself and send command to OpenSprinkler to open zones in any pattern you’d like. A single firmware is not going to fit everyone’s need. The reason we make the whole product open-source is to give users the freedom of modify the software in any way they want.

OpenSprinkler, also its API, is really great. And I am very happy and grateful for being able to use it.

> Also, the firmware supports up to 40 programs, so technically you can create many programs to define when does each group of zones start. So in theory you can use multiple programs to do anything you want. It is certainly tedious and difficult to update this group of programs, but it should be able to achieve what you need.

This is what we do currently. But the 7 Driplines run 1h each, that is, 7h alltogether. Our water pump is rather loud and also takes 800 W. By wiring all together the driplines can run in 1h together.

> If you want to hardwire multiple zones to the same port, please note that a single port can support no more than 2 parallel solenoids. Each solenoid draws 250 to 300mA holding current, and 500 to 700mA impulse current. The triac on each zone cannot drive more than 800mA to 1Amp max, so it can’t do more than 2 zones. You can always use an external relay, which can drive amps or even tens of amps. That way one single zone switches the relay, and the relay in turn switches high current load.

As said, I am not good in electronics. I have a software developer background. The power adapter I have from https://opensprinklershop.de/product/netzteil-24vac-15a-36va/ says:

> Kann bis zu 8 Zonen gleichzeitig bedienen! Siehe unten verlinktes Video!
(English: Can operate/run up to 8 zones simultaneously! See the video linked below!)

This is just for the OSPI. For the PI itself a have a designated USB-C power adapter extra (2A I think).

Also I hardwired the 7 zones today and it seems to be working. So I am a bit confused now whether it is ok or not as you said that at most 2 can be hardwired.

Kind regards, Jens

[Ray]

Did you mean to insert all 7 wires into one single port? Or did you mean insert 1 wire to each port and run them in parallel? I can’t imagine how the former could work, or if it does for a short period of time, how it can work more than a few minutes. If you look at the datasheet of the triac:
https://www.mouser.com/datasheet/2/848/Z0103MN-1846818.pdf
the maximum amount of current it can drive is 1A. If you evenly divide that by 7 valves, each only gets 140mA, which is way below the holding current of a sprinkler valve. This is waiting for trouble to happen, either the triac will burn out, or the solenoids will not reliably open because of the low holding current. Maybe your valve draws less current? Is it a special type of valve that draws less current than other valves? The link you provided cannot be opened so I can’t check its spec sheet.

I am still puzzled by why can’t you use 7 ports and have the zones run in parallel. Is it because you don’t have enough zone ports? You can always get a zone expander to add more zone ports. In the firmware you can set these zones all to parallel, and that way you create a program, run each zone 1 hour, they will all turn on at the same time, so they all finish together. I just don’t understand why this is not a feasible option?

[nachtigall]

Yeah, I inserted 7 wires into one single port. See https://imgur.com/a/EB0rqxh where the black cable goes into port 1 and all 7 wires are hardwired with a WAGO connecting clamp. I tested it about 4 times, but only for 5 minutes (so 4 x 5 min together) and it seemed to be working. This was on May 2. After reading your response I disconnected it again for now (thanks for the Heads up) – better safe than sorry. I hope it didn’t burn anything yet :-/

The valves I use are 100-HV-MM Rain-Bird 24V AC (nothing special as far as I know): https://www.rainbird.com/de/products/ventile-der-serien-hv-und-hvf

What I find strange is that your “fellow” German OpenSprinkler shop sells this AC Adapter (https://opensprinklershop.de/product/netzteil-24vac-15a-36va/) and promotes it with “Can operate/run up to 8 zones simultaneously!” – EDIT: Well, rereading this page now and watching the embedded video it means “Can run up to 8 zones in parallel – but the each zone is connected to 1 individual port”. So this clarifies it…

> In the firmware you can set these zones all to parallel, and that way you create a program, run each zone 1 hour, they will all turn on at the same time, so they all finish together. I just don’t understand why this is not a feasible option?

I already have a zone expander and enough open ports. But I rethought our “problem” over the weekend and maybe I/my family need to change their “mental model” on how we use OpenSprinkler. At the moment me and my family (wife/kids) very often manually start zones (no program) whenever they think this is needed (with the Android app). So they start all dripline zones (group P) and then 2 or 3 sprinkler zones (group A). And they expect the driplines to run in parallel and sequentially followed by the sprinklers. But then driplines (P) will run together with the sprinklers.

We already have separate programs for the driplines and the sprinklers. But – and that’s the change we have to do – we have to make sure that these programs are schedules on completely different days (or times) to make sure they will not run in parallel. And then I will need to tell my family that the “dripline zones” (P) will run in parallel with everything else. So my family can still start the driplines / or dripline program manually but they should wait before they start any sprinklers manually, too. Otherwise they would run in parallel. I think we can change our behaviour here.

Thanks for the input.

[Ray]

OK, now I am able to see the valve’s datasheet, it DOES look like your valve has a lower holding current than typical ones we’ve seen. Yours has a holding current of 91mA (vs. 250mA typical), and inrush current of 290mA (vs. 600mA typical). So it’s about a third of traditional valves. I guess that explains putting all 7 wires into one port works for you. Well I still think it’s a bit risky to put all 7 in one port, but if you can do with 4 zones in one port, that should be relatively safe.

Yes, using a higher current rating transformer means you can run multiple zones at the same time, but not all inserted into one single port. It’s similar to say your house may have a electric panel of 200A, but each individual power socket usually only drives up to 15A. You don’t insert all appliances into one single socket.

I did think about the possible new feature of ‘virtual zones’ where a virtual zone means it maps to several physical zones simultaneously. This is relatively easy to do in firmware, but it will involve some amount of UI work. I will have some free time in the summer and will consider implementing this as a new feature.

[Ray]

I forgot to mention: not sure if this is anything useful to you: although you should’t insert multiple zones into one port, you CAN, however, insert one zone simultaneously into multiple ports (i.e. you split the wire into multiple, so that you can insert them to multiple ports). This allows the same physical zone to be opened by multiple logic zones, so that if any of the ports opens, the physical zone opens. This has been used by some customers in situations where the same zone needs to be associated with different pump/master zones in different programs. For example, if a physical zone A needs to trigger master 1 in program 1, but master 2 in program 2, the current firmware does not allow you to dynamically change associated masters on the fly. But if you insert zone A simultaneously to say, port 5 and 7, and have zone 5 associate with master 1, and zone 7 associate with master 2, then in program 1 you can schedule zone 5 and program 2 schedule zone 7. This way, both programs will result in physical zone A to open, but they trigger different master zones.

[nachtigall]

‘virtual zones’ sounds interesting. I guess that would also solve the issue of being able to reorder stations. That’s another thing I already looked up in the forum in the past and it seems that the easiest way to do this is rewiring the ports. That is, I have a certain logical way the hardwiring is done due to the color codes of the valve cables – and I would not like to change this color order. But for driving the irrigation system and watering the plants/flowers I would like to have a mapping from my hard wired order to something different. Sounds like ‘virtual zones’ could be this flexible software mapping.

But reordering the physical order in software is not a real issue at the moment for me. I just wanted to let you know that ‘virtual zones’ sound interesting from another perspective too.

Thanks for the help and for OpenSprinkler alltogether!

[Author]

Posts