Manufacturers publish datasheets for everything that they make so that we can use the parts as they are intended. How many watts can my transistor dissipate? What pin is the ground pin? How do I communicate with this RTC? Every day in electronics someone is asking how something works. It’s really easy to ask someone else, and then wait for their reply and hope they are right, but we are given tools to use. Nevertheless, it’s a whole new world to try and figure it out on your own.
Make magazine published an article Digital Clock: Programming PIC microcontrollers, part 3 that became my first true adventure in reading datasheets. Since then I have made several digital clocks, and learned how to use several components. To show you a little of what a datasheet can do for you, let’s start with a simple transistor: 2N3904 NPN (click for datasheet).
What can we learn here? The collector, base, and emitter are shown in the first diagram. This is step one is using the 3904 transistor. The Absolute Maximum Ratings are the next important links. The main point I obtain from this datasheet is the max collector current of 200mA. Any more than that, and you’ll have a smoking transistor. As far as the 3904, that is most of the information that I need. If I ever encounter a question, though, I can surely discover it here.
One of the most complicated datasheets that I’ve worked with lately is the SHT11 temperature and humidity sensor. I’ll readily admit that I used an outside source to figure this one out. I’m not sure this would have worked if I didn’t “cheat.” The datasheet was highly confusing to me, but Parallax had one that included their Basic Stamp code. I dissected this to make my own C functions. SHT11 datasheet hosted on www.sensirion.com I purchased one of these from eBay, and it works just like the Parallax one. It only looks a little different. The only thing I really needed to know was how to communicate with it.
Page 5 is where the help begins. Page 5 lists the pin connections for the SHT11. Once connected, I start every command with the connection reset sequence. Then I issue a start command. Once this is complete, the microcontroller issues read commands and receives the information. All the codes are listed on page 6. Check out The SHT11 Temperature Probe Lives!!! This is how I interpreted the rest of the datasheet. In a few weeks, I’ll have the finished product, bill of materials, final schematic, and program files to share with everyone.