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.

18 thoughts on “OpenSprinkler Beagle First Prototype Done

    • October 23, 2013 at 1:17 am

      Well, I kind of like a shorter name, like OS-xx where xx is 2 to 3 letters long.

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  • October 24, 2013 at 7:48 pm

    How about you put BB in front of OS? Then it will be BBOS or in short — “BOS”.

  • October 25, 2013 at 4:53 pm

    I think it is a great idea to add the relay on-board for garage door control. Would it be possible to add at least two relays since the Beaglebone has so many GPIOs? I have two garage doors and would like to have control for both.

    • October 27, 2013 at 4:23 pm

      I can check but I suspect it will be quite tricky as there isn’t much space left on the board to allow for another relay.

  • October 31, 2013 at 8:36 am

    Personally, I’m fond of simply “Sprinkler Beagle” or “OpenSprinkler Beagle” as I’m fond of words rather than letters. I think you can leave out the designation of which board in the name. You could alternatively say “OpenSprinkler Black” as I like that abbreviation better than “BBB”. Your all-letter name could simply be OSB.

    • October 31, 2013 at 11:09 am

      For the full name, I definitely prefer OpenSprinkler Beagle, as it’s clear and short. ‘OpenSprinkler Black’ might sound like it has to do with the color of the enclosure (the current OpenSprinkler enclosure is lightgray-ish).

    • October 31, 2013 at 11:16 am

      Yup, Anthony sent me his post a while ago, and I’ve been reading it. I’ve been programming in Python using Adafruit’s GPIO library, and everything seems to be working fine. The OpenSprinkler Pi code was mostly written in Pyhton, so it’s pretty easy to port them to BBB.

  • October 31, 2013 at 1:49 pm

    Just a thought, you could use the extra long female headers from Major League Electronics and use the same stacking spacers I use in my Dual Motor Controller Cape design (see pictures – These spacers take me about 2 minutes a pair to cut on my Laser Cutter. I can make up a batch of them for you if you want, and you can use it to offset long female headers from the PCB.

    Also, can I carry your OpenSprinkler on my webstore ( I’m trying to carry as much BeagleBone related items as possible. Contact me by email if this is possible to set up.

    Paul Tan.
    Exadler Technologies Inc.

  • November 10, 2013 at 5:11 pm

    A few questions:
    Will the Open Sprinkler Beagle Bone Black have an RTC on it for time?
    I2C? (I already have some Dallas I2C temp sensors I want to wire in).
    Can we purchase the older style see thru enclosures? I saw the new ones are for sale.
    Your enclosure (really nice!) make an excellent general purpose RPi/BBB enclosure for capes and stuff.
    Any guess on ETA date for selling the OSBBBlack? Price? I only need 5 zones, but the above idea of having a relay is, well, excellent!

    I was planning on making a sprinkler with the BBB and the daughter card or cape was going to have a PIC micro controller for ALL of the sprinkler firmware. The BBBlack would be used for internet access with a decent GUI to program the timings, but the timing data would be stored in the PIC EEPROM and the BBBlack could be removed to save power (and the BBB could be used for other stuff). The BBBlack to PIC interface was going to be just RS-232 and only used to write and read sprinkler settings settings like temperature, soil moisture, rain sensor, on/off times, etc. I live in Colorado, and they have water restrictions where you can only water on two specified days of the week, and many simple hose sprinkler timers (most of them) can’t handle that. They do stuff like 1 time per day or 1 time every other day, etc.

    So congratulations on your project as yours is really nice, so I think I just need to buy yours instead of making my own:)

    One other comment:
    I just added drip irrigation for my garden, and squirrels like to chew, eat, dig, etc. So my other plan for my sprinkler was to add one or two motion detectors and turn on the sprinkler for 30 seconds if motion was detected. Stuff like this is almost impossible to do on mainstream home sprinklers, so that was also another reason to build one. I’m hoping your OSBBBlack will at least pass thru some of the GPIO’s/RS-232/I2C/SPI pins so we can add to it.

    • November 10, 2013 at 9:49 pm

      -Yes, there is already a DS1307 RTC with CR1220 backup battery.
      -The older, clear plastic cover will no longer be available as we’ve completely switched to solid colored enclosures.
      -It will be available in less than a week of time.
      -All the pins will be mapped out on the OSBBB board, so you have access to all pins.

      • November 11, 2013 at 2:09 am

        Thanks Ray, it’s great to hear that it has the RTC and all pins available as that makes it fully extendable! So any guidelines on timeline or price?

  • November 11, 2013 at 2:58 am

    One other comment that the OSBBB or any OSxxx board is extremely useful for gardens. I can maybe use a commercial one for my lawn but for my garden the watering really depends on weather, time of year, what is planted, temperature during the day etc to have it hands off and a customizable product like yours makes that possible where commercial ones pretty much ALL fail at and the OSBBB’s primary purpose for me is for the garden as the watering needs change daily and sometimes I have even watered 3 times a day for temperature regulation on really hot days for stuff like lettuce. With the internet connection, it’s probably possible to download local temperatures for feedback into the system, but I realize that’s a custom add on I could possibly later add. Anyway congratulations on making a superb product that fits this need. Hopefully you will later also carry micro pumps with extremely low flow for indoor seeding trays too:) I’ll be looking forward to seeing the layout to see how much room may be available for a daughter card on top for electronic extensions (as you mentioned there was some room on top).

    One other question is temperature on the BBB inside the case since it’s inverted (if it is) – do you have a guess on the ambient temperature around the BBB inside the case?

    • January 1, 2014 at 12:47 pm

      Sorry, I didn’t notice this comment previously. I haven’t tested the temperature on BBB with the current arrangement. I will do some more thorough tests as it gets close to the summer. Thanks.

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