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Comment by Jedd | Hacker News Reader

As always, anyone trying to work with gravity fed systems that sit in the range between ~2 metres head (the usual maximum of very low-head valves) and standard / city pressure, are somewhat stuffed.

I'm working with about 10 metres of head - a decent standing pressure, despite coming through 400 metres of 50mm polypipe - but it's too much for the specialised 'water barrel' type valves mentioned here. Combined with no power (if i had power I'd have a pump :) means it's also not feasible to use always-closed solenoids, or have sufficient pressure to reliably get residential grade water computer valves to open / close.

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Have you tried something like this:

https://www.aliexpress.com/item/Irrigation-water-timer/15107...

Since it's a ball valve operated by a motor it works with zero pressure. It's a relatively small ball valve but should be enough for almost all applications. I have one of those controlling about 100 meters of drip tubing from a source that's not more than 2 meters high (less if the tank is empty) and it works fine. For better flow I'll be trying one of these ball valves:

https://www.aliexpress.com/item/Stainless-Steel-BSP-1-Actuat...

It's much less convenient as they don't have an integrated controller. I'll be trying it with this controller:

https://www.aliexpress.com/item/NO-NC-220-240V-timer-switch-...

and a 12V battery together in a waterproof casing of some sort. I've been looking for a plastic case similar to the water timer one that's a screw on with an o-ring but haven't found one yet.

I used to have the first one, it was garbage - didn't even last an Australian summer, I think it overheated.

That sucks. I've had good luck with the solenoid version of those. But I can see how the fully enclosed design can cause overheating if it's left in the australian summer sun.

I actually picked up a few of the first ones there via ebay a while ago, to trial off a smaller tank with around 2 metre head, but haven't plugged them in yet. Winter means frosts, and no great need for automatic watering. I note someone else has had bad experience with them - I've used the normal pressure versions of those with some success - a couple of years, with 9-monthly battery changes, seems reasonable for the price - just frustrating when they go wrong (usually just before a fortnight of 40+ Celsius days).

The actuator though, that looks very relevant to my interests. I've just done a google spiral on CR02 (and similar) wiring, to control via an arduino, say. With 3s to close / open, and only 12V required, this seems quite feasible to have a cheap solar charged battery sitting and running a half dozen of these of a manifold. The benefits of a switching solenoid in terms of power consumption, with a simpler control mechanism?

The last link you posted seems to imply it will talk to a solenoid (NC or NO) only - would be very curious how that goes.

I have several dozen old water timers with the o-ring seal ... where the o-ring seal has failed, and the insides rusted out. I now cover them all in thick plastic bags, and keep them under pit covers / galv steel lean-tos. Probably explains why they tend to last more than one Australian summer, too.

>The last link you posted seems to imply it will talk to a solenoid (NC or NO) only - would be very curious how that goes.

The way CR02 wiring works is that you have a common ground and then you feed the 12V to one of two wires. The valve takes care of stopping the motor when fully open and fully closed so it should minimize power consumption. So my plan is take that normal NC/NO relay and feed the 12V to the common wire and wire NC and NO to each of the two valve wires. Since the programmable relay itself is also powered by 12V I get away with a single power source. My hope is a simple pack of low self-discharge 8xAA NiMH or similar will last a season. But a 12V lead battery and a solar panel could work as well.

Aliexpress has a very big selection of different kinds of actuated ball valves. If they actually work reliably it seems like a great solution as it's a normal valve operated by a motor. See this for example for a selection of voltages and the 5 wiring types:

https://www.aliexpress.com/item/CWX-25S-mini-electric-actuat...

That one I linked was picked quite carefully to be stainless steel and CR02 wiring which seems to be the easiest to operate with just a single relay. I've received the relay but not the valve yet so I haven't tested everything yet.

>I have several dozen old water timers with the o-ring seal ... where the o-ring seal has failed, and the insides rusted out. I now cover them all in thick plastic bags, and keep them under pit covers / galv steel lean-tos. Probably explains why they tend to last more than one Australian summer, too.

Those are some rough conditions if the o-ring failing is enough to rust everything. I'd expect the threading itself to provide quite a bit of protection already. Can't imagine how you'd get much moisture through all those threads. One thing I have noticed is that you shouldn't torque the lid hard so as to not deform the o-ring too much.

UPDATE: finally got the valve and it works fine with the controller. The combo uses 8mA when closed, ~80mA while opening (for ~5secs) and ~40mA while open (half is the relay in the controller half is the valve). This makes it outside the range of a simple battery but should work fine if you have a solar setup with a 12V battery or an AC mains and a simple 12V power source. So far I'm happy with the domestic all-in-one I linked so I'll probably not pursue this more. If a simple NiMH pack worked I'd probably trial a full setup. But if I was going further I'd use a DIN 12V programmable relay like this:

https://www.aliexpress.com/item/New-DIN-Rail-Time-Relay-Swit...

and a DIN 12V power source like this:

https://www.aliexpress.com/item/DR-15-12-Hot-sales-China-mai...

all enclosed in an outdoor distribution box like this:

https://www.aliexpress.com/item/Free-Shipping-IP66-Waterproo...

That way everything gets properly packaged using DIN elements. If you have a 12V panel/battery you don't need the AC->12V power source of course.

Have you evaluated how much it would cost to use solar power?

Or would the possibility of the system not running be a disqualifier?

Yeah, solar for charging batteries to then run solenoids, absolutely feasible - but most solenoids are either Normally Open or Normally Closed, and need constant power when holding them in the other position. For relatively low-flow situations these are non-starters, as you usually want to have a circuit open for an hour or more.

There are switching solenoids that only draw power as you change state. Downside, they don't fail safe. They're also more expensive, and AFAICT you can't use standard (NC / NO) controllers with them. To complicate matters, switching solenoids usually want a certain amount of pressure (about twice what I'm working with).

It's an area that's slowly getting better served by cheap fab places out of China. You can already get A$20 'residential' grade 13mm single line water controllers that are mostly reliable, but their valve comes down to about a 1mm hole, so big impact on flow rate, and highly susceptible to debris.

What about stuff like holding open a larger solenoid to charge a gravity tank?

> but it's too much for the specialised 'water barrel' type valves mentioned here

what are you using instead?

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