So today I decided to write about a topic I have not mentioned on my blog before and is not Java related. Few months ago, I’ve got my hands on an Arduino compatible board for the first time. I was pretty intrigued to explore what this little guy can actually do and following article is a brief review of my first encounters with micro controllers as such. I was able to try out a few small programs and check basic properties of this board and tried out some sensor work. Reading this article may serve as a teaser for those who are considering jumping into the world of Arduinos and a review of my starting kit of choice for those who are considering any such purchase.
Lets start with the board itself. When it comes to size, this is a mid size board (9.3 x 6.1 mm). Apart from a pretty cool name, Stalker is packed with a number of features build in such as temperature sensor, real-time clock (with a slot for battery), microSD card slot, Bee socket, I2C, user LED and reset buttons for both ATMega328P and Bee module. All of these features work as expected and if you have trouble, you are very likely to receive valuable advice and help from more experienced users on appropriate forums. But the best source to start with is a wiki page that is provided by the producer (contains feature/compatibility list, detailed descriptions, code examples as well as schematics).
Some might say that one the biggest disadvantages of this board is the lack of USB connectivity compared to traditional Arduino boards. However, USB connectivity is still pretty easy to achieve with separate piece of hardware described later. Actually, I find this to be more of an advantage since I do intent to use Stalker as a wireless unit (without the need for USB connection) for my projects.
Waterproof Solar Kit
Even though the Stalker board makes the heart of the kit, there are a few other nice parts as well. This kit contains an enclosure box, battery, solar panel, 2 GB microSD card and UartSBee module.
One of the most interesting aspects of this board are its powering options. First of all, the primary source of power is 3.7V LI-ion battery. However you are not bound to the battery. UartsBee, covered later in the post, is capable of powering your device when you are using it indoors. But Stalker also has a port for solar panel, that is used to charge the battery. After doing some testing, I must admit that I am pretty surprised with the actual power consumption. During sunny days you don’t have to worry about the power. But even moderate sunlight is pretty sufficient to keep Stalker up and running with no problem.
Blogger called Pedantite did his power consumption testing as well and here is what he found out:
In my tests, moderate sunlight was enough to power the board without the battery enough at least to power the Arduino bootloaded. In later tests with my ZigBoard attached, I could operated and receive transmission without the battery attached in strong sunlight. Also, the 5V line that comes from an attached USBee module will charge the battery if your indoors, at night with your kids sleeping (you just feel a little uncomfortable with a “Stalker” around). The charge chip and battery voltage lines are connected to analog ADC lines on the AVR, so you can measure voltage or charge status in code.
Than he continues with:
I wrote a test sketch where I polled, every 10 seconds, the time, temperature, charge and battery state, wrote that to a CSV on the SD, and sent the data over serial to the attached ZigBee. No sleep states were used on board, and the ZigBee slept for 4 seconds out of every 10 seconds interval. From a full battery, I was able to run for 4.5 days with the solar panel face down before it ran out of juice. Nice!
Stalker and some other accessories fit pretty well into this enclosure box. However if your project involves bigger hardware parts or more of them, you will have to look for a workaround or change the enclosure box completely. However it feels pretty sturdy and durable so you don’t need to worry whether it will survive in your garden.
One of the main features of this kit is that it is waterproof. In order to make it waterproof you will need to employ this thin white rubber tube to hold the enclosure sealed tight. The top of the enclosure box it transparent to allow the solar panel to do its job.
I have to say that coding for Arduino is fun. And its also easy to setup and jump right to it. Since Stalker does not have any USB ports build directly into it, this kit comes with this little handy gadget to help us out. As you probably guessed from the shape this is another Bee module called UartsBee. This module connects to Stalker by a six pin cable and to your computer using mini USB cable (both included in the kit). When it comes to programming itself it business as usual. You need to have your Arduino development IDE and UartsBee drivers properly installed in order to successfully push your code to the board.
If you don’t have any experience with Arduino programming don’t worry. Manufacturer provides pretty good documentation in form of wiki pages to get you started with a handful of small programs to showcase all the main features of this board and also to get you acquainted with many useful libraries you might need to start with your own projects. Generally speaking this wiki is best place to start looking when you are starting out and need to do some experimenting.
One nice way to customize the behavior of your board is to employ jumpers. I found two really practical modifications I used right off the bat. Lets take a closer look.
Battery charging status LED jumper
Its kinda nice to see battery charging status without using dedicated code/sketch just to do so. Probably that is the reason for having two dedicated LEDs for this kind of indication. However many projects involve placing your hardware in some remote or hard to reach location rendering this feature useless. So to provide users with a way to save some power, Stalker allows you to disable these LEDs by cutting the track connecting the CH_STATUS pads to disconnect these LEDs from C_VIN. There is no need to worry that you will stay in the dark when it comes to analyzing your power consumption since there is a library that will help you with that called Battery Library.
DS3231 Interrupt jumper
I find this to be one of the most useful modifications one can do to their Stalker board. Even though the power management is pretty satisfactory its always a good idea to mind your power consumption. By soldering PD2 and INT pins of INT jumper you connect DS3231 interrupt out pin to ATmega328 INT0 pin. This allows you to put your hardware to sleep and only awake it when you really need it based on time events from the real time clock module. This way you can be sure to have your setup do its jobs only when needed. I used this technique when I was doing some research work for my plant growing project which I intent to share with you as soon as I am finished with it.
After all testing and playing around I must say – this was fun. This kit costs 60 dollars and I feel its worth every penny. It was useful as a learning platform and I am ready to put it in use with my first project.