The OpenSprinkler controller

This article is being written in a part of the world with limited rainfall — a near-desert environment. That notwithstanding, the local humans have reached the conclusion that it would be a good idea to surround their homes with lush, green vegetation that evolved to thrive in a rather more humid environment, and which requires fairly intensive life support — and water pumped from the other side of the continental divide — to survive here. Western civilization, it seems, depends on us continuing to do this; otherwise we would surely not continue to put so many resources into it.

Providing life support to vegetation by dragging a hose around quickly loses any charm it may have once had, so the installation of automated sprinkler systems is common in these parts. The control system takes the form of a timer that, traditionally, has been programmed through a painful combination of dial turns and button pushes; anybody who has tried to figure out how to configure a bicycle computer (speedometer) will understand. More recently, of course, we have seen the advent of smart controllers that are said to make this process easier and to enable control of the system while vacationing in a distant location. The allure of being able to soak a Colorado front yard while lounging on a South-Pacific beach is, seemingly, irresistible.

These "smart" controllers have all of the afflictions of other IoT products. Their security is questionable at best, as is the security of the cloud-based systems they connect to — and store their data on. The cloud service itself exists at the whim of the vendor and can vanish at any time, turning a smart controller into a remarkably dumb brick. Any data collected by these devices is centrally stored and routinely exploited by unknown third parties. Occasionally, the device will cease functioning until an "upgrade" is applied (assuming the owner is asked about the upgrade at all) that adds new behaviors that the owner never asked for or wanted. An Internet failure can lead to a sprinkler failure, turning one's bit of American paradise into a forlorn dustscape.

All of this can make the old way of knobs and buttons look appealing.

OpenSprinkler appears to be an attempt to do things better. The device itself is based on an ESP8266 controller, and the hardware design is freely available (though with an unspecified license). The firmware that runs the device is available under GPLv3, and the mobile app carries the AGPLv3 license. There is a version of the software that can run on a Raspberry Pi for those who want to put together their own controller.

The hardware, as shipped, can manage up to eight zones; expansion modules (one is shown in the photo) can bring that number up to 72 — far more than your typical hardware-store sprinkler timer. The device has inputs for two sensors, either for rainfall or ground moisture. It has a built-in WiFi interface, and a version with a wired Ethernet port is also available.

The device lacks a display that is usable for more than the most basic of tasks, though; in an era when we all carry interaction devices in our pockets, that is seemingly unnecessary. Initially, the controller comes up in access-point mode; the owner can put their device onto that network and configure the controller. It is, indeed, possible to keep it in the access-point mode forever, at which point it can function with no supporting systems other than the device used to communicate with it.

More likely, though, one will want to put it onto the local WiFi network, which is easily accomplished; after that, the access point is shut down. The controller can display the IP address it was assigned on its tiny display; any web browser that can reach that address can be used to configure it. The Android app (which is not available via F-Droid despite being free software; it can be had via the Play Store) can scan the local net and find the controller automatically; after that it presents a screen that is essentially identical to the web interface.

The first configuration step, naturally, is to set a password on the device; a good password, after all, is the only thing preventing your jealous neighbors from learning your top-secret watering strategy or programming the device to turn the flower garden into a swamp. The dashboard screen shows the state of all zones (or as many as will fit on the screen) and allows individual zones to be run with a couple of clicks.

The programming interface is flexible, allowing the creation of multiple, named programs, each of which has its own zone list and watering schedule. Both day-of-week and every-Nth-day programs are supported — an important feature in locations where watering restrictions (imposed on those rare occasions where, say, the ability to put out fires is deemed to be even more important than green grass) require one or the other. There is an overall scaling feature for seasonal adjustments, and watering can be deferred based on input from either sensor (if any are connected).

The device will, by default, use NTP to keep its clock adjusted, sparing one from the shame of sprinklers that start five minutes too late. It is also able to connect to Weather Underground, download weather data, and adjust watering according to a number of different algorithms. There are options for connecting to remote logging servers to enable, for example, a sprinkler-status window in one's home automation dashboard. Assuming one has such a thing, of course.

It is, in other words, a capable and fully featured sprinkler timer. But that is not really the point here; this is not the Lawn Watering News. The real point is that OpenSprinkler is a device that one can buy or build independently, with open-source firmware that can be modified and updated at will, with an entirely optional, open-source app, that can be operated entirely without the use of any sort of cloud service whatsoever. That seems like a good demonstration of how the Internet of Things could work, at least for certain classes of devices.

One does not often need to control sprinkler systems from far away, in your editor's experience; it is more of an on-the-scene job. Should the need arise, though, there are a couple of options. One is to expose the built-in web server to the Internet, perhaps by poking a hole through the router firewall. Given the (presumably) low level of security auditing this device has received and the complete lack of any sort of security update mechanism, that may not be the wisest of ideas.

As an alternative, the OpenThings Cloud (OTC) service can be used as an intermediary. This service runs a simple proxy server, licensed under GPLv3. Unless one exposes the painfully long token assigned by this service, that will effectively block all unwanted access to the device (which will still require a password from anybody who gets through, of course). One can simply trust the OTC server to actually be running the posted software and not secretly monitoring whether your are watering your roses sufficiently; alternatively, setting up an independent server on a low-end cloud instance would be a straightforward task.

The end result is a device that uses open hardware and software to do a useful job in a way that respects its owner. OpenSprinkler is capable enough at its core task to stand out, even for users who do not care about the other aspects. But for those of us who prefer our computers (and our homes) to be under our control and serving our interests — rather than those of one or more random corporations — OpenSprinkler is truly a breath of fresh air. We do not actually need to embed computers in everything around us but, when that is a useful thing to do, this is an example of how it should be done.