Announcing OpenSprinkler Beagle (OSBo) v1.0

  • OpenSprinkler Beagle kit is available for purchase at Rayshobby Shop.

Following the sneak-peak preview, I am excited to announce that OpenSprinkler Beagle (OSBo) v1.0 is now officially released! OpenSprinkler Beagle is an open-source sprinkler / irrigation extension board for the BeagleBone Black. It uses four GPIO pins to control an unlimited number of sprinkler valves. Using this board, you can easily convert your BeagleBone Black into a low-cost, web-connected smart sprinkler controller. You can use online weather data to help regulate sprinkler water time, and remotely change settings and programs when you are traveling away. Best of all, it’s an open-source project — you are welcome to tinker with the hardware and/or software to create your own customized sprinkler controller.


The idea of OpenSprinkler Beagle came from the OpenSprinkler Pi, which is a sprinkler extension board for the Raspberry Pi. Since OpenSprinkler Pi was released earlier this year, it has been a very popular product. Over time I’ve received requests from users to develop a similar board for the BeagleBone Black. While the BeagleBone Black is similar in nature to the Raspberry Pi (i.e. both are low-cost embedded Linux boards), it offers some interesting benefits such as a large number of GPIO pins, build-in analog pins, build-in eMMC, microSD card slot (i.e. smaller profile). faster CPU etc. Undoubtedly it makes sense to develop an OpenSprinkler variant for the BeagleBone Black.

The hardware design of OpenSprinkler Beagle is similar to OpenSprinkler Pi: it contains a 24VAC to 5VDC switching regulator, shift register, triac, DS1307 RTC with CR1220 battery, zone expansion board connector. It also currently shares the same enclosure as OpenSprinkler Pi. But it also offers several improvements, specifically:

  • Added a total of 10 bidirectional TVS for protection against transient voltages: one for each of the eight stations, one for the 24VAC port, and one for the rain sensor port.
  • The BeagleBone Black is now plugged down into OSBo, and all GPIO pins are mapped out to the pinout area.
  • Added a 5V mini-relay for more general-purpose switching. The relay has a contact rating of 120VAC / 2A. It can be used for switching low-power lighting, or garage doors etc.
  • The 24VAC terminal block is changed to orange color with 3.96mm pin spacing. This helps prevent incorrect connection to other terminal ports. There is also a solder-on 2A fuse on the 24VAC line.
  • Added a rain sensor port with pull-up and current limiting resistors.

Below is an annotated diagram that shows the various components of the board:

OpenSprinkler Beagle Homepage

Below I am going to give a very brief overview of the hardware and software setups. For details, please watch the tutorial video above, and visit the official OSBo homepage at

Hardware Setup

The hardware is pretty easy to set up. The kit comes with an assembled OpenSprinkler Beagle circuit board, enclosure, screws, terminal blocks, and extra pin headers in case you want to map out additional GPIO pins. In addition, you need to provide a BeagleBone Black, a nano-size WiFi dongle, and a 24VAC sprinkler transformer (these are not included in the kit and need to be purchased separately). The board makes use of the first 2×10 pins on port P9 of the BeagleBone Black for interfacing with shift register, RTC, rain sensor port, and mini-relay. Plug in the BeagleBone Black into OSBo, connect the 24VAC power, plug in the common (COM) wire and individual station wires, and that’s it. The interface is the same with other sprinkler controllers. If you have a rain/freeze sensor, you can connect it to the rain sensor terminal.

Software Setup

Follow the recent update on OpenSprinkler Pi, the software setup for OSBo has also been made a lot easier. Specifically, I’ve created a SD card image with pre-installed software. Download the image, burn it to a microSD card, pop it in to your BeagleBone Black, and you are ready to go. The pre-configured SD card runs a Ubuntu operation system (default user name ubuntu, password temppwd), and sets Dan’s interval_program to start by default. As soon as the system has booted and is up online, you can open a browser and type in http://x.x.x.x:8080 (where x.x.x.x is your BeagleBone’s IP address). This will bring up the interval program’s web interface. The interval program has a rich set of software features, such as setting multiple sprinkler programs, preview programs, run-once program, manual operation, logging, rain delay etc. The details are all explained in the user manual of the interval program.

The SD card has also pre-installed Samer’s mobile web app, which provides a nice front-end for mobile devices such as pads and phones. It is available at http://x.x.x.x/sprinklers.

In addition, there are three demo programs installed in the /home/ubuntu/demos/ folder. There is a self-test program, a relay test program, and a Google Calendar-based sprinkler program, which makes use of a Google Calendar for scheduling water events. I’ve received many good comments regarding the Google Calendar-based program — while it looks simple, it’s quite convenient to use and very suitable for the less technical minded people.

Since the software is pretty much all adapted from OpenSprinkler Pi, feel free to refer to the OpenSprinkler Pi documents if anything is unclear. I will try to make the OpenSprinkler Beagle website more self-contained, and it will have to be polished over time.


In the previous post, I asked for naming suggestions. Thanks to everyone who made comments there. After careful thoughts, I’ve decided to use the full name OpenSprinkler Beagle, and short name OSBo. Particularly, the short name OSBo is picked because it goes well with OSPi (OpenSprinkler Pi), is easy to distinguish with OSBee (openSprinkler Bee), and Bo is a name of a dog. So overall I consider this to be the top choice.

Thanks for reading this post. If you are interested in buying the OpenSprinkler Beagle, we have a limited number of kits immediately available, at the first link below. Feel free to leave comments and suggestions below or at the Rayshobby Forum.


OpenSprinkler Beagle First Prototype Done

Update: OpenSprinkler Beagle is officially released, and is available for purchase at Rayshobby Shop.

A lot of prototype PCBs arrived over the weekend. Among them is my long-waited OpenSprinkler Beagle — a sprinkler / irrigation extension board for the BeagleBone Black. Cool, time for some prototyping actions!


The design of OpenSprinkler Beagle largely follows OpenSprinkler Pi (OSPi). As usual, the board contains a 24VAC to 5VDC switching regulator, shift register, triacs, terminal blocks, and zone expansion board connector. It provides 5V power to the BeagleBone Black, uses 4 GPIO pins (specifically P9_11, 12, 13, 14) to interface with the shift register, and SDA2/SCL2 to interface with the DS1307 RTC. Since the BeagleBone and RPi are similar in size, I can reuse the same enclosure as I’ve been using so far.

There are also several changes and improvements. First and probably the biggest design change is that the BeagleBone Black is now oriented face-down, and it plugs directly to the extra long male pin headers as you can see on the pictures above and below. In contrast, on OSPi, the Raspberry Pi is oriented face-up, and connection from RPi to the board is through a pair of 8-pin and 3-pin cables. The biggest advantage of the face-down design is that it saves the cables, and there is now some extra space in the upper-half of the enclosure, making it possible to add additional modules. To make it easy to reuse the available pins on the BeagleBone, I’ve also mapped out all the 46 pins on ports P8 and P9 to the pinout area.

I actually wanted to use the same design for OSPi, but it’s more tricky because RPi uses male pin headers, which means the extension board will have to provide female pin headers. I haven’t been successful at finding extra long female pin headers, but I will keep looking.


Among the other changes: the 24VAC port is now using a new type of terminal block that has different pin spacing and color with the others. This will reduce the chance of accidentally plugging 24VAC into the COM or rain sensor port, which has happened before. Speaking of rain sensor port, yes, there is now a rain sensor terminal — it takes one extra GPIO pin, but there are plenty of GPIO pins on the BeagleBone, so who cares 🙂

Also, I’ve added a 2A fuse, and nine 48V bidirectional TVS (transient-voltage suppressor) — one for the power in, and one for each of the eight zones. This will provide some level of protection to the circuit during power surges and lightening. In the past I’ve used MOVs (metal-oxide varistors). Those are pretty cheap, but they are bulky and have to be hand-soldered since they are through-hole components. TVS is a bit more expensive but can be easily automated using pick-and-place machines.


Also, the analog-digital converter (ADC) has been removed since the BeagleBone has built-in analog pins. As sort of an experiment, I also removed the on-board DS1307 RTC, but instead added pin headers to plug in an external RTC module, as you can see close to the top of the PCB. This was done as an experiment to empty out some space on the PCB to allow future expansion. But it turns out to be not very successful, because the module actually takes quite some space and makes it difficult to close the top cover.

Here are some additional pictures of the assembly:

I quite like the overall design. There are a few minor changes I want to make before the official release. For example, the 100uF capacitor is currently too close to the BeagleBone’s USB port, and it needs to be moved further away. Also, I can make the PCB color black to match the color of the BeagleBone Black. By the way, I learned from the forum that some users want to use the sprinkler controller to control garage doors. I figured it’s it’s pretty easy to add a relay on the board for general-purpose applications. So I am gonna try to add that too.


What would be a good abbreviated name for OpenSprinkler Beagle? Since it’s designed for the BeagleBone Black, I could call it OSBBB, but I want to distinguish it from another product I am working on — the OpenSprinkler Bee (OSBee). OSBBB and OSBee are too close with each other to pronounce. One possibility is to call it OS-Bo, which would put it nicely in a series with OS-Pi and OS-Bee. If you have better suggestions, feel free to leave a comment below. Thanks!

Update: OpenSprinkler Beagle is officially released, and is available for purchase at Rayshobby Shop.