#183 - For Immediate Release, Patent US3808385
The Sprinkler Nerd ShowApril 11, 202511:3615.92 MB

#183 - For Immediate Release, Patent US3808385

Could we create a smarter, data-driven rain sensor that actually logs rainfall events, provides historical context, and informs better irrigation decisions?

For immediate release—breaking news, kind of.

In this solo episode of The Sprinkler Nerd Show, Andy dives into what seems like a revolutionary product: a mechanical rain sensor that requires no batteries, no Wi-Fi, no firmware updates—just pure, functional design. It shuts off irrigation during rainfall and turns it back on when conditions dry out, all thanks to hygroscopic discs that expand and contract to trigger a simple switch.

This device sounds like the newest drop in water-saving technology—until Andy reveals the twist: it's not new at all. In fact, it's based on US Patent 3,808,385, filed in 1972 and granted in 1974. That's over 50 years ago. And the core concept of the mechanical rain sensor hasn’t changed since.

Andy breaks down how the device works, why it’s still effective today, and what it says about the pace of innovation in the irrigation industry. He challenges contractors and tech developers alike to ask the big question: why are we still using 1970s technology in 2025?

Could we create a smarter, data-driven rain sensor that actually logs rainfall events, provides historical context, and informs better irrigation decisions? If so—why hasn’t anyone built it yet?

Key Highlights:

  • Breakdown of how the moisture-responsive switch actuator works

  • Benefits for contractors: simplicity, reliability, zero maintenance

  • Installation and adjustment tips

  • Why the current state of rain sensors is a wake-up call

  • A challenge to the industry: let’s rethink how we track rain and respond to it

Andy closes the episode with a call to action for all Sprinkler Nerds: always ask why. Why things work the way they do, why they've stayed the same—and how we can make them better.

[00:00:19] Welcome back to the Sprinkler Nerd Show. I'm your host, Andy Humphrey. And today we're going to talk about a brand new patent. I just discovered why it is important. And I'd like to share with you what I learned about it and why it might have value for you. So let's get into today's topic of Patent US3808385.

[00:00:53] If you are an irrigation professional, old or new, who designs, installs, or maintains high-end residential, commercial, or municipal properties, and you want to use technology to improve your business, to get a leg up on your competition, even if you're an old-school irrigator from the days of hydraulic systems, this show is for you.

[00:01:16] This is for Immediate Release. You are hearing this first on the Sprinkler Nerd Show, the place for irrigation innovation. Let's get started. 2025 just got a whole lot smarter for irrigation professionals. Imagine. Imagine. Imagine a rain sensor with no batteries, no Wi-Fi, no firmware updates,

[00:01:41] and yet it knows exactly when to shut your sprinklers off and when to bring them back online. The latest breakthrough in water-saving tech uses simple materials and mechanical precision to automate rain shutoff, reducing overwatering and eliminating the unnecessary callbacks. It's rugged, affordable, and field-ready. Just an elegant solution for contractors who just want things to work.

[00:02:10] There's no apps, no nonsense, it's just smart design. Introducing the all-new moisture-responsive actuator switch, US Patent 3808385. What is this invention, you ask? Well, this device is a moisture-sensitive shutoff switch for irrigation systems.

[00:02:35] It's a mechanical rain sensor that automatically disables sprinklers during rainfall and reactivates them when things dry out. It doesn't rely on electronics or power or software. Instead, it uses hydroscopic disks, materials that swell when wet, to physically press a switch and interrupt power to the irrigation system.

[00:03:01] When the disks dry out, they shrink, and the system comes back online just like that. But simple, easy, breezy, lemon-squeezy, reliable, low-cost, just easy. So, let's talk about how it works for you technical contractors. So, inside this device is a standard micro switch that connects to the irrigation controller. And then, on top of that switch, is a vertical stack of special absorbent disks.

[00:03:30] So, when it rains, the disks soak up water and they expand. It's this expansion that pushes against a spring-loaded mechanism, and that activates the switch and cuts power to the irrigation systems. When those disks dry out, that's typically around 8 to 20 hours, depending on airflow, humidity, wind, etc.,

[00:03:57] they shrink back and the switch resets and watering resumes. There's an adjustable housing that allows contractors to fine-tune the air circulation, controlling how quickly the disks dry up and the system comes back on. Let's talk about adjusting and the installation of this new device. You can mount it anywhere, like a fence post, wall, garage.

[00:04:24] Just make sure it's exposed to the rainfall. Perfect place is not, I repeat, is not under the gutter. So, connect in line with the controller's terminals, then set your drying delay by rotating the outer housing to let in more or less airflow. It adjusts the disk's preload with a locking nut to control how sensitive the switch is to moisture,

[00:04:53] aka rainfall. So, why does this matter to you? Well, there's no wiring complexity. It works with simple two wires or standard controllers. There's no maintenance. There's no batteries. There's no sensors to fail. No maintenance. It's field-adjustable dry time. Perfect for different climates and different install sites. Best part? It's affordable. Great for those retrofits or budget-conscious systems.

[00:05:22] And it's durable. It's made from fungus-resistant, live, lifelong materials. Well, I guess we'll see how long-life the materials are. But really, guys, the key takeaway here is that in an industry chasing digital everything, this ultra-practical device is a refreshing reminder that smart doesn't always mean high-tech.

[00:05:50] It's reliable, field-tested, in tune for exactly what irrigation contractors need. Predictable, automatic shutoff in response to weather. But wait. There's more. No. No, there's not. But there is a twist. What's the twist? Well, this new tech for immediate release is not so new at all.

[00:06:17] Well, what I just described to you is a patent. Again, U.S. Patent 3808385. Go ahead and look it up. Google Patent 3808385. Was actually filed in 1972. And it was granted in 1974.

[00:06:44] That's over 50 years ago. And yet, it still holds up as one of the most clever, efficient solutions to rain shutoff on the market. Are we still using what I read to you just now? What I described to you? Yes. For 50 years, the rain sensor, for all practical purposes, has not changed.

[00:07:12] And what I find interesting about the rain sensor is that it's almost like it's not a sensor. I mean, I guess it is a sensor because it is actuated by the sensing of rain or the touch of rain. But it doesn't record anything, right? A rain sensor doesn't tell us how much it rained, how fast it rained, the intensity of the rain.

[00:07:40] There's no actual information that comes out of the mechanical rain switch. And to me, that's the preferable way to describe the device. It's not so much a rain sensor. It's a mechanical rain switch or a mechanical moisture-activated switch. It is a switch.

[00:08:08] It is not adjustable digitally, if that's the right word. You can adjust it mechanically on sight, but with very little precision. And so I guess I just, I ask, I ask us, I ask industry, why? Why are we still using a device from 1972?

[00:08:35] What parts of an automobile are exactly the same as they were in 1972? I don't know, but I would imagine that my windshield wipers might be a little bit different. And you know what? Today, our cars can sense the rain and automatically actuate the windshield wipers.

[00:09:02] So it's just a good, I'm just putting this out here because something so simple as the rain sensor hasn't changed. And I do not have an answer to why, other than that's just the way it's done. And in this industry, the green industry, landscape industry, and for most construction industries, the way something's done is how something's done. So I challenge you, let's go make a new rain sensor. How could we improve the rain sensor?

[00:09:32] Wouldn't it be amazing if you could put a little wireless sensing device out at your customer's property and allow it to actually record real data and bring that real data into a platform that you could use to make decisions with? The fact that rain sensors simply actuate a switch is not that smart.

[00:09:56] They work well for what they are, but there's so much more that we could improve upon at very little cost, right? The fact that a wireless rain sensor still costs somewhere between $125 and $200. There's no reason that we shouldn't put little micro weather stations on properties and actually pull in that data and actually start charting that information on top of our runtimes.

[00:10:24] There's no reason that we shouldn't be doing that. The only reason is no one has done it. So I challenge you, let's do it. Let's make something better. How can you improve upon that? So that's my solo episode for today. And again, I think that in many ways, just this, the forgotten invention, even though it's not forgotten, but the fact that the rain sensor was invented in 1972 is, you know, kind of serves as a reminder

[00:10:54] that one of the core problems in irrigation hasn't changed all that much. And that sometimes the best ideas don't come from cutting edge tech, but from brilliant simplicity. So that thank you guys very much for listening. Always ask why question everything that you do question everything that somebody tells you. Ask why? Ask why again? Be curious? And that's it.

[00:11:23] Challenge you ask why to everything. See what happens so long. Thank you for listening. See on the next one. Bye-bye.