Converting AC Irrigation Valves To DC Operation

February 9, 2026 by Lewin Day 31 Comments

Due to historical engineering decisions made many decades ago, a great many irrigation systems rely on solenoid valves that operate on 24 volts AC. This can be inconvenient if you’re trying to integrate those valves with a modern smart home control system. [Johan] had read that there were ways to convert these valves to more convenient DC operation, and dived into the task himself.

As [Johan] found, simply wiring these valves up to DC voltage doesn’t go well. You tend to have to lower the voltage to avoid overheating, since the inductance effect used to limit the AC current doesn’t work at DC. However, even at as low as 12 volts, you might still overheat the solenoids, or you might not have enough current to activate the solenoid properly.

The workaround involves wiring up a current limiting resistor with a large capacitor in parallel. When firing 12 volts down the line to a solenoid valve, the resistor acts as a current limiter, while the parallel cap is initially a short circuit. This allows a high current initially, that slowly tails off to the limited value as the capacitor reaches full charge. This ensures the solenoid valve switches hard as required, but keeps the current level lower over the long term to avoid overheating. According to [Johan], this allows running 24V AC solenoid valves with a 12V DC supply and some simple off-the-shelf relay boards.

We’ve seen similar work before, which was applied to great effect. Sometimes doing a little hack work on your own can net you great hardware to work with. If you’ve found your own way to irrigate your garden as cheaply and effectively as possible, don’t hesitate to notify the tipsline!

A Guide To Using Triacs For Switching AC

January 18, 2026 by Bryan Cockfield 14 Comments

For switching high-powered loads from a microcontroller, or for switching AC loads in general, most of us will reach into the parts bin and pull out a generic relay of some sort. Relays are fundamental, proven technologies to safely switch all kinds of loads. They do have their downsides, though, so if you need silent operation, precise timing, or the ability to operate orders of magnitude more times you might want to look at a triac instead. These solid state devices can switch AC loads unlike other transistor-based devices and [Ray] at OpenSprinkler is here to give us an overview on how to use them.

The key to switching an AC load is bi-directional conductivity. A normal transistor or diode can only conduct in one direction, so if you try to switch an AC load with one of these you’ll end up with what essentially amounts to a bad rectifier. Triacs do have a “gate” analogous to the base of a bipolar junction transistor, but the gate will trigger the triac when current flows in either direction as well. The amount of current needed to trigger the triac does depend on the state of the switched waveform, so it can be more complex to configure than a relay or transistor in some situations.

After going through some of the theory around these devices, [Ray] demonstrates how to use them with an irrigation system, which are almost always operating on a 24VAC system thanks to various historical quirks. This involves providing the triacs with a low voltage source to provide gate current as well as a few other steps. But with that out of the way, switching AC loads with triacs can become second nature. If you prefer a DC setup for your sprinklers, though, [vinthewrench] has demonstrated how to convert these sprinkler systems instead.

DIY, Full-Stack Farm Automation

January 16, 2026 by Bryan Cockfield 13 Comments

Recently, [Vinnie] aka [vinthewrench] moved from Oregon to Arkansas to start a farmstead. This is a style of farming that focuses not just on a profitable farm where produce is sold at market, but also on a homestead where much of one’s own food is grown on the farm as well. Like any farm, though, it’s extremely hard work that takes a tremendous amount of time. Automation and other technology can make a huge impact in these situations, and [Vinnie] is rolling out his own software stack to help with this on his farm.

He calls his project the Pi Internet of Things, or PioT, and as its name suggests is based around the Raspberry Pi. Since this will all be outdoors and exposed to the extremes of Arkansas weather, everything built under the auspices of this project prioritizes ruggedness, stability, and long-term support, all while avoiding any cloud service. The system also focuses on being able to ride through power outages. The server side, called piotserver, uses a REST API to give the user access to the automation systems through a web interface

[Vinnie] also goes into detail about why existing systems like Home Assistant and Open Sprinkler wouldn’t work in his situation, and why a ground-up solution like this is more appropriate for his farm. This post is largely an overview of his system, but some of his other posts go into more detail about things like integrating temperature sensors, rainfall monitoring, controlling irrigation systems, and plenty of other farm automation tasks that are useful for any farmer or gardener.

We’ve also seen some other projects of his here like this project which converts a common AC sprinkler system to an easier-to-use DC system, and a DIY weather station that operates in the 915 MHz band. He’s been a great resource for anyone looking to have technology help them out with their farm or garden, but if you’re just getting started on your green thumb be sure to take a look at this starter guide as well.

Field Guide To North American Crop Irrigation

September 3, 2025 by Dan Maloney 26 Comments

Human existence boils down to one brutal fact: however much food you have, it’s enough to last for the rest of your life. Finding your next meal has always been the central organizing fact of life, and whether that meal came from an unfortunate gazelle or the local supermarket is irrelevant. The clock starts ticking once you finish a meal, and if you can’t find the next one in time, you’ve got trouble.

Working around this problem is basically why humans invented agriculture. As tasty as they may be, gazelles don’t scale well to large populations, but it’s relatively easy to grow a lot of plants that are just as tasty and don’t try to run away when you go to cut them down. The problem is that growing a lot of plants requires a lot of water, often more than Mother Nature provides in the form of rain. And that’s where artificial irrigation comes into the picture.

We’ve been watering our crops with water diverted from rivers, lakes, and wells for almost as long as we’ve been doing agriculture, but it’s only within the last 100 years or so that we’ve reached a scale where massive pieces of infrastructure are needed to get the job done. Above-ground irrigation is a big business, both in terms of the investment farmers have to make in the equipment and the scale of the fields it turns from dry, dusty patches of dirt into verdant crops that feed the world. Here’s a look at the engineering behind some of the more prevalent methods of above-ground irrigation here in North America.

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Automated Drip Watering Device Keeps Plants Happy

January 20, 2023 by Lewin Day 10 Comments

Plants tend to need a regular supply of water to stay happy. If you’re a green thumb, it’s one of the primary things you should take care of before you go on holiday. This DIY plant watering system from [Jaychouu] offers to handle just that.

The system consists of a soda bottle acting as a water container, and an electronically-controlled valve to control the flow of water to plants. Irrigation of the plants is via dripper nozzles to provide a small but consistent feed to the plants. The use of drippers tends to disturb the soil less than pressurized jets of water. A soil humidity sensor is used to detect moisture levels and avoid over-watering. There’s also a capacitive water level sensor that fires off a warning when the reservoir’s water level is low. An ESP32 serves as the brains of the operation, allowing remote control via Blynk.

If you’re looking for a simple way to drip water your plants while you’re away, it’s hard to go wrong with this concept. If you feel like a more passive solution though, we’ve seen other viable methods too.

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Irrigation Controller Uses Google Calendar To Make Things Easy

February 20, 2020 by Lewin Day 18 Comments

Irrigation controllers have been around for a long time, often using similar hardware inside that would be familiar to the average maker. However, many of the products on the shelf at your local hardware store can be quite expensive for what amounts to a microcontroller, display, and relay board. [oscillatory] had such a rig, but wanted to bring it into the 21st century, IOT style.

The existing Holman irrigation system consisted of a control box, hooked up to four solenoid valves controlled by relays. [oscillatory] decided that replacing this with something fancier would thus be straightforward. A relay board packing an ESP8266 was sourced, and flashed with the Tasmota firmware. This was then hooked up to run off the Holman’s 24 VAC supply via a CCTV power supply, allowing the new controller to be run in parallel with the existing hardware, just in case. Scheduling is then controlled by Google Calendar, in concert with Home Assistant.

[oscillatory] now has a watering system that can be controlled over the web, and without the need to install any custom apps. Simply creating a calendar entry is enough for the system to spring into action. We’ve seen others use a similar approach, too. It’s a great example of using off-the-shelf parts to whip up a useful custom home automation setup!

Vinduino Water-Smart Farming – Now With LoRa!

October 25, 2018 by Roger Cheng 9 Comments

Our five rounds of Hackaday Prize 2018 challenges have just wrapped up, and we’re looking forward to see where the chips fall in the final ranking. While we’re waiting for the winners to be announced at Hackaday Superconference, it’s fun to take a look back at one of our past winners. Watch [Reinier van der Lee] give the latest updates on his Vinduino project (video also embedded after the break) to a Hackaday Los Angeles meetup earlier this year.

Vinduino started with [Reinier]’s desire to better understand what happens to irrigation water under the surface, measuring soil moisture at different depths. This knowledge informs more efficient use of irrigation water, as we’ve previously covered in more detail. What [Reinier] has been focused on is improving usability of the system by networking the sensors wirelessly versus having to walk up and physically attach a reader unit.

His thought started the same as ours – put them on WiFi! But adding WiFi coverage across his entire vineyard was not going to be cost-effective. After experimenting with various communication schemes, he has settled on LoRa. Designed to trade raw bandwidth for long range with low power requirements, it is a perfect match for a network of soil moisture sensors.

In the video [Reinier] gives an overview of LoRa for those who might be unfamiliar. Followed by results of his experiments integrating LoRa functionality into Vinduino, and ending with a call to action for hackers to help grow the LoRa network. It sounds like he’s become quite the champion for the cause! He’s even giving a hands-on workshop at Supercon where you can build your own LoRa connected sensor. (Get tickets here.)

We’re always happy to see open-source hardware projects like Vinduino succeed, transitioning to a product that solve real world problems. We know there are even more promising ideas out there, which is why Hackaday’s sister company Tindie is funding a Project to Product program to help this year’s winners follow in Vinduino’s footsteps. We look forward to sharing more success stories yet to come.

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