A good first step in a project is knowing what you want to do. [Ben Fino] made it clear that his Raspberry Pi Sprinkler control system for his wife’s garden had one goal: keep the plants alive. The resulting project is doing just that and no more.
The circuitry, and plumbing, is straightforward and explained well in the Instructable. All the electronics consists of is the Pi and a MOSFET to take the 3.3v GPIO to 5v to control a relay. The valve controlling the water requires 28v AC which necessitated the relay to control it. There are also three LEDs: one is for power, one to indicate when the valve is opened, and one is an extra for some future purpose.
The intriguing part is the use of weather data from the web to determine if it’s rained recently. Python scripts provided by [Ben’s] friend [Mark Veillette] use a weather site API to get the rainfall data. The main script is set to run once every 24 hours. [Ben] set his system to water unless the previous day had sufficient rain. How much rain and the number of look-back days is programmable.
What a great application of the KISS principle: keep it simple, stupid – except for that third LED without a purpose.
Internet is taken for granted. These days you assume there is Internet and only wonder if there is free WiFi to get onto it. But in the early days, connecting to a network could be tough and this was particularly true in Serbia. The country’s Internet revolution was complicated by both technology and politics, but the vibrance of the tech community always found a way.
The story is a fascinating one shared by Dejan Ristanovic at the Hackaday | Belgrade conference. He is now the Editor-in-Chief of PC Press computer magazine and played an integral part in providing global email access to Serbia. Enjoy the video of his talk below and join me after the break for a few highlights.
You want to put your credit card number into a web site. You know to look for a secure web site. But what does that really prove? And now that so many electronic projects have Web servers (ok, I’ll say it… the Internet of Things), do you need to secure your web server?
There was a time when getting a secure certificate (at least one that was meaningful) cost a pretty penny. However, a new initiative backed by some major players (like Cisco, Google, Mozilla, and many others) wants to give you a free SSL certificate. One reason they can afford to do this is they have automated the verification process so the cost to provide a certificate is very low.
Of special interest in the new 2Ku system is the antennas strapped to the top of a GoGo-equipped plane’s fuselage. These antennas form a mechanically-phased-array that are more efficient than previous antennas and can provide more bandwidth for frequent fliers demanding better and faster Internet.
Currently, GoGo in-flight wireless uses terrestrial radio to bring the Internet up to 35,000 feet. Anyone who has flown recently will tell you this is okay, but you won’t be binging on Nexflix for your next cross country flight. The new system promises speeds up to 70Mbps, more than enough for a cabin full of passengers to be pacified by electronic toys. The 2Ku band does this with a satellite connection – much faster, but it does have a few drawbacks.
Because the 2Ku system provides Internet over a satellite connection, ping times will significantly increase. The satellites GoGo is using orbit at 22,000 miles above Earth, or about 0.1 light seconds away from the plane. Double that, and your ping times will increase by at least 200ms compared to a terrestrial radio connection.
While this is just fine for email and streaming, it does highlight the weaknesses and strengths of mobile Internet.
Back in 2007, [Stathack] rented an apartment in Thailand. This particular apartment didn’t include any Internet access. It turned out that getting a good connection would cost upwards of $100 per month, and also required a Thai identification card. Not wanting to be locked into a 12-month contract, [Stathack] decided to build himself a directional WiFi antenna to get free WiFi from a shop down the street.
The three main components of this build are a USB WiFi dongle, a baby bottle, and a parabolic Asian mesh wire spoon. The spoon is used as a reflector. The parabolic shape means that it will reflect radio signals to a specific focal point. The goal is to get the USB dongle as close to the focal point as possible. [Stathack] did a little bit of math and used a Cartesian equation to figure out the optimal location.
Once the location was determined, [Stathack] cut a hole in the mesh just big enough for the nipple of the small baby bottle. The USB dongle is housed inside of the bottle for weatherproofing. A hole is cut in the nipple for a USB cable. Everything is held together with electrical tape as needed.
[Stathack] leaves this antenna on his balcony aiming down the street. He was glad to find that he is easily able to pick up the WiFi signal from the shop down the street. He was also surprised to see that he can pick up signals from a high-rise building over 1km away. Not bad for an antenna made from a spoon and a baby bottle; plus it looks less threatening than some of the cantenna builds we’ve seen.
When [William’s] thermostat died, he wanted an upgrade. He found a few off-the-shelf Internet enabled thermostats, but they were all very expensive. He knew he could build his own for a fraction of the cost.
The primary unit synchronizes it’s time using NTP. This automatically keeps things up to date and in sync with daylight savings time. There is also a backup real-time clock chip in case the Internet connection is lost. The unit can be controlled via the physical control panel, or via a web interface. The system includes a nifty “vacation mode” that will set the temperature to a cool 60 degrees Fahrenheit while you are away. It will then automatically adjust the temperature to something more comfortable before you return home.
[William’s] home is split into three heat zones. Each zone has its own control panel including an LCD display and simple controls. The zones can be individually configured from either their own control panel or from the central panel. The panels include a DHT22 temperature and humidity sensor, an LCD display, a keypad, and support electronics. This project was clearly well thought out, and includes a host of other small features to make it easy to use.
[The Backwoods Engineer] tested out a new accessory kit for the STM32-F4 Discovery board. The image above shows two boards communicating with the UDP protocol. Notice the extra PCB into which each Discovery board has been plugged. This is a third-party add-on which adds Ethernet, RS-232, SD card slot, and a connector for LCD or Camera. We’ve had one of these F4 Discovery boards on hand for a while and haven’t figured out a good way to connect external hardware to the huge dual pin-headers. This doesn’t solve the problem — the base board also includes dual headers to break-out all the pins — but having Ethernet, serial, and SD certainly reduces the need to add all that much more. The other drawback to the hardware is that the sample firmware is targeted at the IAR Embedded Workbench which is neither free, nor in the realm of affordable for hobbyists.
The NIC used on the baseboard has auto-crossover capabilities so the boards were connected using a regular Cat6 patch cable. This example has the boards constantly sending UDP packets with the module on the right reporting status information to a terminal via the serial connection.