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I had an amazing day visiting Worthington Assembly Inc. (WAi) — an electronics manufacturer / circuit assembly company located in South Deerfield, MA. It’s only 15 minutes of driving from Amherst, where I live. I first saw their business name when I was reading Ryan O’Hara’s post about how he got his RGB-123 LED matrices manufactured. I must have had a lousy day then, because I failed to notice the location of the company, and had always thought it’s in Boston. Then last night when Andrew Seddon, CEO of CircuitHub.com, pinged me about PCB manufacturing and mentioned WAi, I suddenly came to realize that they are located right next to me. Gosh, I felt completely dumb that I didn’t find this out earlier!

Anyways, I couldn’t bear with the temptation to check out their facilities, so I paid a visit right away this morning. It really made my day — the beautiful pick and place machines, conveyor belt reflow oven, selective soldering machine, it’s like a dream circuit assembly house I’ve always wanted. Chris Denney (CTO) gave me a tour around the house. I was too engaged in the conversations and didn’t take as many pictures as I wanted. But here are a few:

On the left, Quad QSP-2 picker that’s being retired (at the end of the picture is their Vitronics Soltec reflow machine); on the right: through-hole component insertion machine.

MyData picker that’s currently in service. This one can pick 8 components at a time, and has a super fast vision system that does alignment in real time. It also has a mechanical alignment system, and a component checking system that can read component values (e.g. resistance, capacitance) on the fly. Amazing!


Selective soldering machine, and PCB cutter.

Very satisfying. I can even imagine the next batch of OpenSprinkler to be assembled right here. Then I can just drive up in 15 minutes to pick up the order. How cool is that :) They take both large-quantity and small-quantity orders, down to even just 1 board, surprisingly. Of course the cost of making just 1 board would be quite high, compared to making 100, where the same overhead cost will be amortized.

Right now they are in partnership with CircuitHub.com to make the service available to makers and hardware startups. If you have circuit assembly need and don’t have the resources to make them yourself, or if you have the resources to make a few but not hundreds, you should definitely give it a try. Just log in to CircuitHub.com (with your dropbox account) and upload some Eagle project files. The user interface is very clean and friendly. It links to Octopart.com to grab component prices in real-time. You can then adjust the order quantity and lead time. Kudos to Andrew for building such a slick website.

I was very well treated, had Polish beer with Neil, Rafal, and Chris; and by the end of the day, I even got two free T-Shirts. Cool. Picture moment!

A new day, a new post. Today’s post is about the new OpenSprinkler Zone Expansion Board v2.0, with injection-molded enclosure and 16-station capability. The injection-molded enclosure provides a coherent look with the OpenSprinkler main controller; and the 16-station capability adds twice as many stations as before, without taking extra space.


As I briefly talked about in a previous post, this new version 2.0 is only slightly larger than the previous version 1.1, but can handle twice as many stations. You can think of it as basically two 1.1 boards (8 stations) squeezed together onto a single board that’s roughly the same size as before. What made this possible is a clever design that makes use of the same four support pillars to both attach the top and bottom pieces together, as well as secure the PCB inside the enclosure. This saves some space normally reserved for the PCB screws. The design was proposed by Xavier at SeeedStudio — the principal industrial designer for the project — and it follows the same design adopted for the OpenSprinkler enclosure.

Also, version 2.0 has included per-station bidirectional transient voltage suppressor (TVS) for added electric protection. These are essentially diodes can clamp the voltage if it exceeds a threshold in either direction. This can reduce the chance that a high transient voltage or lightening damages the circuit or the sprinkler solenoid.


In terms of usage, version 2.0 is the same as 1.1. It works for all of OpenSprinkler, OSPi and OSBo. Use the 2×4 extension cable to link the OUT port of the main controller to the IN port of the expansion board. Additional expansion boards can be daisy-chained in the same way — by following the OUT -> IN links. Because 2.0 and 1.1 have the same cable wiring, they can be mixed and used together.

The firmware currently does not automatically detect the number of stations. So you need to keep in mind that each 2.0 counts as 2 expansion boards (2x 8) in the option settings.

Because of the difficulty in stocking both versions, we have discontinued 1.1 and are only offering 2.0 now. Price-wise, it is a little more expensive than 1.1. So if you only need 8 extra stations, sorry, you have to pay the extra to get 2.0. But if you need a larger number of extra stations, this is a great deal because it’s considerably cheaper and saves a lot of space too.

OpenSprinkler Zone Expansion Board v2.0 is available for purchase at the Rayshobby Shop. We offer bundled discount if you are buying it together with any OpenSprinkler main controller, including OpenSprinkler v2.1s, DIY v2.1u, OSPi and OSBo. Be sure to check the “Add Zone Expansion Board Options” when you purchase. Thank you!

I am very excited to announce that the OpenSprinkler native mobile app is now available on all platforms (iOS, Android, Windows Mobile). A big shout-out to Samer Albahra for his diligent and absolutely fantastic work in developing this app!

Different from the previous OpenSprinkler web app, the native app can be installed as a standard app on your mobile device. This not only enables some new features (such as automatic scanning device, multi-language support) right away, but opens doors for more exciting features in the future, such as push notification and local storage (e.g. representing each station with a photo icon). The app is free, so go ahead and give it a try right now!



Let me briely go through the requirements for using the app:

  • Hardware: to use the app you need to have either an OpenSprinkler (v2.0 and above), or OpenSprinkler Pi (OSPi, any version), or OpenSprinkler Beagle (OSBo, any version). Even if you don’t have the hardware, you can set up a software simulation (Dan’s interval_program) on RPi or BeagleBone to try out the firmware and app. OpenSprinkler hardware v1.x is currently not supported. Sorry!
  • Firmware: the app requires OpenSprinkler firmware 2.0.4. If you don’t have this version, please follow the firmware update instructions to upgrade your firmware.
  • App Installation: search for ‘opensprinkler’ in iOS App Store, Android Play Store, or Windows Phone Store, and you should be able to find and install the app.
    • If you like the app, please give a +1 to show your appreciation of Samer’s work!
  • Port Forwarding (optional): unlike the previous web app, you don’t need to set up port forwarding any more if you are accessing the controller within your home network. However, if you want to access the controller outside of your home network (say, when you are traveling), you still need to set up port forwarding on your router. This requires knowing your OpenSprinkler’s IP address and port number (default is 80). Please refer to your router’s user instructions. You can also use dynamic DNS service (such as dyn.com, freeDNS etc.) to set up an easy-to-remember DNS name for your router. Most routers support dynamic DNS service as well.

NOTE to keep in mind: the app provides an alternative front end to the OpenSprinkler controller. The default front end, which is the controller’s webpage (accessed by typing in the controller’s IP in a browser), is still available and functioning. Any operation you apply through the app will also be reflected in the default front end.


The app has a number of notable new features:

  • Scan For Device: on first-use of the app, you need to input information about your OpenSprinkler device, normally the IP address and device password. Samer found a very clever way to quickly scan the local network and automatically find your OpenSprinkler device. This saves your work of having to find the IP address yourself.
  • Multi-Device Support: the app supports multiple device configurations. This is very useful if you have multiple OpenSprinklers and want to access each individual within the same app.
  • Multi-Language Support: this is another exciting new feature — the app provides language localization. There are currently six supported languages: English, Spanish, Hungarian, German, Italian, and Chinese. Big thank-you to Balazs for starting this feature and Samer for continued development. The translations are mostly provided by the users — for those who have contributed: thank you!


These are just some of the highlights I would like to bring to your attention. There are plenty of other features that really make the app stand out, such as automatic count-down timer, easy editing of station names and programs, intuitive program preview, instant launch of any existing program (not just the run-once program), import/export configurations. You’ve got to try it out yourself to find out.

To find out additional details, please go to Samer’s website. Discussions of ongoing development are available at the Rayshobby Forum. Samer is continuously supporting the app development. Please kindly leave your comments and suggestions, either in the comments section below, or on the forum. Thanks!

Curious what the next version of OpenSprinkler Pi (OSPi) is going to look like? Here is a sneakpeak preview of version 1.4:


Wait a minute, what is this strange looking board?! And the Pi is installed at an angle? What’s happening here? Well, the new design is all centered around one simple goal: to fit OSPi and RPi into the existing OpenSprinkler injection-molded enclosure. There are many good reasons to do so. The first is cost reduction: the current OSPi uses the Serpac WM032 enclosure with custom cutouts. This is quite expensive to make. On the other hand, the microcontroller-based OpenSprinkler already has an injection-molded enclosure (and I paid a good amount of money for the mold!), so it makes sense to consolidate the design to use the same enclosure. This will bring down the cost quite a bit. Using the same enclosure also gives both products a consistent look. In fact, in the near future OpenSprinkler Beagle will also adopt the same enclosure, and hence all three will have the same exterior look.

Design Story

The ‘why’ part is easy to explain. But the ‘how’ part proves to a non-trivial engineering challenge. When I was first fiddling with the idea I didn’t think it was at all possible. After all, the injection-molded enclosure was made before OSPi came into place, naturally it was not designed with RPi in mind. It turns out that, due to the positions of the support pillars, the enclosure is just a little bit too narrow to fit RPi at a straight angle. Ouch! But after staring at it for a while like a geometric puzzle, I was delighted to find out that if you rotate RPi by 3 to 4 degrees, it fits perfectly! This gave me inspiration to further develop the idea. It also explains why the Pi has to be installed at an angle, as the picture at the top shows.


In fact, by carefully positioning the Pi, the Ethernet cable can also fit, albeit through the USB cutout instead of the RJ45 cutout. It’s a bit tricky to figure out the position precisely, but I am glad that after two rounds of prototypes I finally got it right :)


Of course since OSPi doesn’t have buttons and LCD, some of the cutouts are useless. I am not completely sure what to do with the LCD cutout. If I leave it alone, it looks quite ugly (see picture on the left below). So my temporary solution is to just put a sticky label at the back, thus covering the big empty hole (see picture on the right below). Eventually I think it’s best to put some graphic design here. I am undecided what to put here. It shouldn’t be the OpenSprinkler logo as the enclosure already has a printed logo. If you have suggestions, please leave them in the comments section. I would greatly appreciate it!


Next, because the injection-molded enclosure is not high enough, I cannot continue using the current design where the Pi faces up and connects to OSPi through ribbon cables. It’s necessary to flip the Pi and plug it into OSPi facing down. This will reduce the height of the overall assembly. However, there is one additional complication: the USB, Ethernet, and composite video connectors on the Pi are all quite tall, so it’s necessary to make cutouts on the OSPi PCB to allow these connectors to sink below the board. The picture on the left below shows the back of the PCB, and you can see where the connectors go through the board.


As the Pi is now facing down, it’s not easy to access the GPIO pins directly. Therefore I’ve mapped out all the 2×13 pins on the Pi to the pinout area, seen at the top-left corner of the PCB.

The last bit of the puzzle is the SD card. Since the enclosure has very limited space, it’s not possible to fit a full-size SD card, without making a cutout on the side. So we need a low-profile SD card. There are several options, one is this microSD to SD adapter. It’s basically a microSD card slot soldered onto a PCB shaped like an SD card but half the size. This and other similar adapters are readily available online and they work reasonably well.


While Googling ‘low-profile SD card’, I found an surprising solution that’s dead simple. In case you don’t know this already: many full-size SD cards are actually half empty. What this means is that the useful stuff (namely the chip and connectors) only take half the space, while the other half has nothing in it! As a result, you can safely cut half of the card away, thus making a low-profile SD card without any adapter. This also has the advantage of preserving the high performance of a full-size SD card (while the microSD card is considerably slower). The downside though, is that if you ever need to insert the SD card to your computer’s SD card slot, you will have to tape the other half back, so that it extends to the original length. Otherwise it will be too short to push in and pop out.


Anyways, this is the end of the story. I admit the new funky design feels a bit forced: it’s born out of the need to re-use the injection-molded enclosure, which wasn’t designed with OSPi in mind. But I am quite excited that I figured out all the pieces of the puzzle. Eventually I may pay a sizable chunk of money to order a new mold dedicated to OSPi, but before that happens we have to stick with the existing resources :)

The hardware components remain largely the same with version 1.3. The only difference is that the relay has been upgraded to a slightly bigger, 250V / 3A type. I am also considering adding a pin header for the nRF24L01 transceiver, to make it possible to communicate with our upcoming products such as OpenSprinkler Bee. Pending a few minor tweaks, things should be finalized within a month or two. Please leave your comments and suggestions, as this will be the last chance to influence the final design of 1.4. Thanks!

The past week has seen some nice community contributions to SquareWear 2.0. The first is a 3D printed strap-on case designed by Paul Modiano:

Very nice and makes SquareWear truly wearable :) The add-on module in the picture is an ADXL335 accelerometer which takes analog pins A4, A2 and A3. The 3D files can be downloaded from Thingiverse. Thanks Paul for designing this case!

Next is an April fool’s day prank created by Steve Edwards. I don’t have a picture of it, but here is Steve’s description from the comments section:

Great platform for April Fools.

I wrote a sketch that ‘delays’ for 3 hours (to give you a chance to hide the Square and for the victim to fall asleep) and then runs 2 tasks:

1) Every x seconds, beep y tones, of z frequency where x, y, and z are random()ized.

2) Every hour blast out 30 random frequency tones to make sure the victim is awake.

Also, before each tone is played, I check to see if the light sensor is less than 2 so if the victim turns on the lights to look for it, it stops ‘beeping.’

I hid 3 in my son’s room. He didn’t think it was so funny :)

Sounds like a fun gadget to annoy someone :)

I also got an email from Pete Metcalfe who wrote a temperature display demo using SquareWear 2 and the chainable LED matrix. He made a compact display by creating a new, 3×5 pixel array of numbers. The source code is posted below.


I am so glad to see SquareWear 2.0 being gradually picked up by the community, and the interesting applications created and shared by users. More to come later!

// Pete's temperature display demo
void loop(){
float temp = (float)analogRead(PINTEMP);
temp = (temp * 3.3 / 1024 - 0.5) / 0.01; // MCP9700.MCP9700A
// define a 3x5 pixel array
int nums[10][13] = {
{ 0, 1, 2, 7, 9,14,16,21,23,28,29,30,30}, //0
{ 1, 8, 9,15,22,28,29,30,30,30,30,30,30}, //1
{ 0, 1, 2, 7,14,15,16,23,28,29,30,30,30}, //2
{ 0, 1, 2, 7,14,15,16,21,28,29,30,30,30}, //3
{ 0, 2, 7, 9,14,15,16,21,28,28,28,28,28}, //4
{ 0, 1, 2, 9,14,15,16,21,28,29,30,30,30}, //5
{ 2, 9,14,15,16,21,23,28,29,30,30,30,30}, //6
{ 0, 1, 2, 7,14,21,28,28,28,28,28,28,28}, //7
{ 0, 1, 2, 7, 9,14,15,16,21,23,28,29,30}, //8
{ 0, 1, 2, 7, 9,14,15,16,21,28,28,28,28} //9
int dig10 = int(temp/10);
int dig1 = temp - (dig10*10);
for(int i = 0; i < 13 ; i++){
for(int i = 0; i < 13 ; i++){
void clearStrip(){
for(int i = 0; i < strip.numPixels(); i++){

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