Famously, Nikola Tesla won the War of the Currents in the early days of electrification because his AC system could use transformers to minimize losses for long distance circuits. That was well before the invention of the transistor, though, and there are a lot of systems that still use AC now as a result of electricity’s history that we might otherwise want to run on DC in our modern world. Sprinkler systems are one of these things, commonly using a 24V AC system, but [Vinthewrench] has done some work to convert over to a more flexible 24 VDC system instead.
The main components of these systems that are set up for AC are solenoids which activate various sets of sprinklers. But these solenoids can take DC and still work, so no major hardware changes are needed. It’s not quite as simple as changing power supplies, though. The solenoids will overheat if they’re fully powered on a DC circuit, so [Vinthewrench] did a significant amount of testing to figure out exactly how much power they need to stay engaged. Once the math was done, he uses a DRV103 to send PWM signals to the solenoids, which is set up to allow more current to pull in the solenoids and then a lower holding current once they are activated.
With a DC power supply like this, it makes it much easier to have his sprinkler system run on a solar powered system as well as use a battery backup without needing something like an inverter. And thanks to the DRV103 the conversion is not physically difficult; ensuring that the solenoids don’t overheat is the major concern here. Another great reason to convert to a DIY sprinkler controller is removing your lawn care routine from an unnecessary cloud-based service.
There might be some relevant code in the DIY fuel injection peojects. Some fuel injectors are driven the same way, high current to activate and lower current to hold.
I started with a “gateway timer” that had a photocell to detect sunrise and a knob to set run-time. Now I have a dual zone that connects to a hose bibb. But obviously I need to move up to the big boy multi-zone machine.
Sadly the big downfall is the logic behind the user interface. Usually it is convoluted and not obvious what is set and when.
I like OpenSprinkler. RaspberryPi based, open source hardware and software (natch), plenty of zones, expandable, and the remote interface is all hosted on the Pi.
The only drawback is there is no good interface on the Pi itself. There’s a two line LCD and a couple of buttons, and if you remember the click-A-while-holding-B nonsense you might be able to run a zone, or maybe stop one. Normally you’d just pull up the interface on your phone, but that doesn’t work for the irrigation maintenance contractors. All they know is Hunter or whatever brand they service.
My pool pump has a touch screen LCD for programming and reviewing programming. ($200 upgrade) I wouldn’t think that such a thing is out of reach for a Pi based system.
Never heard of OpenSprinkler but will check it out.
I have been considering the esp32 version of OpenSprinkler or just doing a Tasmota version to get a nice Matter integration
One could argue that setting up a solar powered system is the ultimate anti-cloud-based system.
ok ok ok… I’ll see myself out…
One of the more interesting things in modern sprinkler systems is a lot of newer ones use a digital protocol to run a ring of two wires around an area, instead of one. Valves are either addressed via stand-alone decoders in the valve box (you run 2-wire to the decoder, and then wire the traditional valves to the decoder), or now increasingly via decoders built into the valve.
Valves and decoders are programmed digitally, via addresses (similar to how 1-wire works), into the controller.
Since its a digital signal, it also supports bi-directional communication. So a valve can report flow, stuck state, temperature, etc.
Sadly its not exactly a standard system yet, although there is overlap between manufacturers. RainBird and Hunter make most of the 2-wire systems, although I believe K-Rain and others support it as well. That said, things like OpenSprinkler do not support it, as far as I know. But given OpenSprinkler is completely open, from hardware on up, you could probably add support relatively easily.
That, or just use 1-wire or similar bus protocols for your sprinkler and have the next owner of your property hate you.
I have experimented with running 24v AC solenoids off DC. I cant remember the resistance and impediance of the coils and calculated the DC equivalant over 50Hz but I found by experimentation that most of my (admittedly cheap) valves ran fine on 12v but a few required more up to 18V to reliably turn on. I never noticed a heating problems however the valves were only on for about 10-20 mins. When testing I can confirm that the turn on current is much higher than holding current, and capacitor helped for low current battery sources.
The real problems is that these valves are power hogs and quite unsuitable for battery operation. From memory I think the specs said that were rated at about 500mA but would mostly work at 100mA and lower for holding.
The solution was latching or pulse valves from China. Much cheaper than Australian sourced valves. These could run at 5V with a short ( few mSec) on pulse and no holding current. The different timing and current requirements meant that my commerical watering system did not work. However ESPhome has a Sprinkler Component that supports pulse operated valves (and deepsleep) . This way you can have a battery operated system, controlled by WIFI. ESP’s are still pretty power hungry but with appropriate deepsleep and a small solar panel they can run on batteries.
You do realize that this has already been addressed by major manufacturers. You can buy replacement DC solenoid for Hunter and Rainbird valves pretty easily. They make their own battery and solar powered controllers as well
I changed from solenoid valves to motorised ball valves https://core-electronics.com.au/solenoid-valve-dn20.html
I had issues with the solenoid valves not properly shutting off under low pressure water. Plus these are very efficient on DC power usage.
My son got some replacement solenoids for regular Orbit valves. They are DC, they worked fine on 12v. A pulse turned them on. A pulse of the opposite polarity turned them off. No power required to maintain state.