Logging is a useful feature which allows you to find out how OpenSprinkler has worked say, in the past week. While you can check the scheduled water programs using the ‘Program Preview’ feature, it does not account for dynamic changes like rain delay, power loss etc. This is where logging comes in handy: you can find out what OpenSprinkler has actually done in the past. Unfortunately I have not been able to include logging in the firmware because of the memory space that it would require to store the log data.
Recently, David Gustavson, an OpenSprinkler user, successfully implemented logging by using a PHP script that he wrote. The way it works is to have a computer that periodically polls the OpenSprinkler status say, every 20 seconds, and the script checks the differences between every two consecutive polls to record status changes. This is quite clever, as it does not require any modification on the OpenSprinkler side. All that it needs is for OpenSprinkler to return the status of each station, which it already does. Of course this does require a computer running on the side (or even remotely), but it’s pretty easy to set up, and you can use a plug computer or a Raspberry Pi which has very low power consumption.
David is kind enough to share his scripts and I’ve checked them in to the OpenSprinkler GitHub repository under the script/PHP/ directory. He also wrote a blog post about OpenSprinkler, which you can read about here. Thanks David!
I have a new toy that came in two weeks ago: it’s a Full Spectrum 40W hobby laser cutter! It has been sitting in the shipping box for all this time. This weekend I finally gather everything I needed to set it up, and here are some fresh-made engravings:
Not too bad for the first try, isn’t it?
Impression. My order was handled very quickly. I placed the order on a Tuesday after 5pm and it was shipped the same day! A big thumb-up to the Full Spectrum team. A week later, the box showed up at my door. It’s quite big and heavy. I mean, this is already the least expensive, hobby level model on the market. I can easily imagine how daunting the professional level ones must be.
Setup. The build quality is pretty good. The exterior could probably use some more sexy design, but at its price level, I have no complaint. To set it up, I bought a stainless steel table from Ikea, a 5-gallon bucket with cover from Lowes, and five gallons of distilled water. The user manual stressed everywhere that you must use distilled water and not tap water. It is used to cool down the laser tube. I guess distilled water is crucial to avoid sediments.
The user manual is a bit confusing and not entirely consistent. Some pictures do not match my model I ended up having to check some youtube videos and forum posts to figure things out. Also, the instructions for installing the beam combiner are almost unreadable due to low toner. This is a bit disappointing. The good news is that these instructions are all available online, so it’s not a big deal.
There are three peripheral devices I set up first: air compressor, water pump, and exhaust fan. Air compressor is the easiest: just connect the air tube and that’s all. For setting up water pump, I cut three holes on the cover of the bucket, so that the in/out tubes and the power cable can go through the cover easily. Then I placed the water pump in the bucket, and poured 5 gallons of distilled water. The exhaust fan is also fairly easy to set up. The only tricky part is to find a way to vent exhaust air to the outside. My solution is to use a piece of cardboard paper and cut it to the right size so that it can fit tightly on my window. Pictures are included:
Running. The first thing to do is to manually move the Z-table in order to get the laser focused onto the engraving surface. I followed the instructions to do a fire test and it worked right away. Keep in mind that the water pump, air compressor, and exhaust fan MUST be running before the laser fires. Also make sure that the emergency stop is deactivated, and the laser switch is activated. The control is done through USB port, which is very convenient. (I remember my hobby CNC machine requires a hardware parallel port, which was a pain to find). The software is only available on Windows. Since I am mainly using Linux these days, I had to salvage an old Windows PC for this. I suspect I can probably run it through a Virtual Windows on my Linux machine too. The software is reasonably good. It did give me annoyance like hanging and crashing, but nothing that can’t be fixed by restarting the laser cutter and software. Here is a video demo of the machine in action:
As you can see, my first test case is to engrave the OpenSprinkler logo (courtesy of Nathan Johnson) onto the project enclosure. It took me a few tries to find the right laser power level and speed. No rocket science. The enclosure material is probably not best designed for laser engraving, because it can easily burn and produce a greenish color. But at the appropriate laser intensity, it looks reasonably good.
The next order I ship will include this engraved project enclosure 🙂 I can probably start making a small batch of engraved enclosures if it turns out to be reasonably productive.
My next steps are to try laser cutting, and installing the beam combiner. Overall I am pretty happy with this new toy. Given that this is the first time I’ve ever used a laser cutter, I would say the installation and initial tests went very smooth. Again, a thumb-up to the Full Spectrum team.
Recently I received a request to customize OpenSprinkler for a 12V DC external relay board. It turns out to be relatively easy to do. Since it may be useful for other folks, I am writing a post here to briefly describe the modifications. First of all, the relay board has built-in opto-couplers and flyback diodes. It is designed to work directly with microcontroller pins. This particular relay board I received is an active low type. This means normally the relay control pin is pulled high; when the control pin is set low by the microcontroller, the relay will be activated. So before you go ahead and make changes, make sure to find out the type of your relay board.
OpenSprinkler can run on 12V DC power supply without any modification. As long as you keep in mind the polarity, it should work right away. Even if you connect the power supply in the wrong direction, it shouldn’t cause any damage because there is a protecting diode D1 that prevents reverse polarity. The only modification I needed to do is to replace the triacs (used to drive AC solenoids) by NPN transistors. Any common NPN transistor is fine. For example, 2N3904. The remaining step is to connect the station wires to the corresponding relay control pins.
The way it works is that normally the shift register outputs low. So all NPN transistors are turned off, and the collectors are pulled high by the relay board. When a station is open, the shift register pin outputs high, turning on the corresponding NPN transistor, and driving its collector low (to ground). This in turn activates the relay. That’s it.
Here is a video showing the relay board in action. The OpenSprinkler running a self test that turns on each station for 3 seconds.
It is also possible to use the NPN transistors to directly drive the relays. However, in this case, you need to add an additional flyback diode (between the collector of the transistor and the +12V line). The flyback diode is important to protect the transistor under inductive load. To accommodate this, I am planning to add PCB holes for these diodes in the future, which will make it easy to solder these extra components.
OpenSprinkler’s 1-year anniversary! Yes, on Oct 9 last year, the OpenSprinkler project got posted on Hackaday and became known to the world for the first time. A lot of updates have happened during this past year. The hardware has gone through four cycles of changes, and the latest version is 1.4. From August 2011 we have started producing the surface mount version of 1.4, making it easier to manufacture and assemble the kit. The software has also been substantially improved. Many user-requested features have been included. I am proud to say that at this moment OpenSprinkler is probably the best Internet-based sprinkler timer with its price and the functionality it provides. I am hoping that in the upcoming years it will start making a positive impact on the technology innovation in consumer-level sprinkler products.
To honor the 1-year anniversary, all orders placed on Oct 9 (today) and 10 will receive a 10% discount. If you have ever considered buying OpenSprinkler but hasn’t made up your mind, there is no better deal than this!
Statistics wise, most OpenSprinkler orders came from the United States, which is not a surprise since we are based in the US. But OpenSprinkler has also reached places outside of the US. So far it has reached close to 30 countries. Here is an un-ordered list: Germany, Netherlands, Australia, South Africa, France, Bulgaria, Spain, Slovakia, Canada, UK, Finland, Portugal, Hungary, Singapore, Belgium, New Zealand, Italy, Turkey, Greece, Peru, Switzerland, Cyprus, Ukraine, Denmark, Estonia, Poland, Austria. I have also marked them on a world map, to give you a better visual:
I want to take a moment to thank the open-source movement. I am a strong supporter for open-source hardware and software. I believe open-source is important for pushing technology innovation and for promoting and implementing new ideas as quickly as possible. Unlike large-scale closed source products, open-source products are often started with a low budget and produced in small batches. We typically assemble kits on the level of a couple hundred per batch. This is how we can quickly update the design, fix bugs, introduce new features, and shorten the overall design cycle. If a particular design didn’t work out, we can simply abandon it and move on. There is little risk of losing big investment money. Also, having a project open-sourced makes it possible for the public to scrutinize the design, identify issues, contribute to the project, and build new projects. As a college educator, I am keen at understanding the underpinnings of how electronic products work, but more than that, I am keen at giving out the knowledge that I know.
Update: OpenSprinkler 2.0 or above uses a different switching regulator and does not require additional resistor any more. The information below is only relevant to OpenSprinkler 1.x.
As you know, OpenSprinkler uses a single 24VAc sprinkler transformer to power both the circuit and the sprinkler solenoids. Frequently people are using a WiFi adapter together with OpenSprinkler to provide wireless Ethernet connection. So how about using the same transformer to also power the WiFi adapter? Ah ha, good question. This turns out to be possible and quite easy to do!
The basic idea is that many of these WiFi adapters (such as the popular NetGear WNCE2001) can be powered using an attached USB cable. One end of the cable is a USB Male A connector, and the other end is typically a 2.5mm power jack that goes into the adapter. Since OpenSprinkler has a built-in USB port (which is connected to the +5V output of the 34063 switching regulator), it can be used to directly power the WiFi adapter. However, OpenSprinkler’s USB connector is a Female B type, so the trick to make this work is to throw in a USB Female A to Male B converter, as shown in the picture below:
You can get this converter from Rayshobby Shop or at online retail stores.
Hold on one second, this is not the only thing you need to do. You also have to solder an additional 1 ohm resistor to the circuit board. The reason is that these WiFi adapters are quite power hungry: I measured that the NetGear WNCE2001 draws about 300-400mA current during operation. On the other hand, OpenSprinkler (by default design) outputs about 330mA current on its +5V output, of which 180mA will have to power the mcu and Ethernet controller. So we need to increase the current output. Fortunately this is not too difficult to do. The trick is to reduce the resistance of Rsc — current limiting resistor for the 34063 switching regulator. According to 34063’s datasheet, the maximum output current is 0.33/Rsc. So if we put two 1 ohm resistors in parallel, Rsc is effectively 0.5 ohm, and hence the maximum output current increases to 660mA, enough to power both the circuit board and the WiFi adapter. Also, OpenSprinkler v1.3u and v1.4 have already designed a spare slot for the parallel Rsc, so it’s pretty easy to make the modification.
You can reduce Rsc even further to provide better safety margin. 34063 supports maximum output current of 1.5A. To do so, you can keep putting more 1 ohm resistors in parallel until you reach the desired resistance. The reason to use multiple 1 ohm resistors is because it’s lowest value common resistor. Anything below 1 ohm will have a big price jump.
Again, if you are interested in trying this, you can get the USB converter from Rayshobby Shop. We will also throw in a couple of 1 ohm resistor free of charge!
