2a: Say “Hello World” with Blinky

Almost every introductory computer programming course starts off with “Hello World.”  This is a very simple program that simply prints the words “Hello World” on the screen. In electronics, we have “Blinky.”  A simple circuit that makes an LED blink.

There are tons of ways this can be achieved, but one of the easiest to teach is by using a chip called a 555 timer, a few resistors and a capacitor.

We’ll start by introducing our “Blinky on a Breadboard”.

Most circuits will start off as napkin sketches like this one:

Getting the idea down on paper as early as possible and adding to it while you pore over datasheets is an important step.  It’ll give you something to go back to if something goes wrong.  This circuit should blink an LED approximately 21 times per second.  Kind of fast, but it keeps the capacitor small.  Now let’s put the circuit together on the breadboard and make sure it works.

… And there it goes:

So now we know our napkin sketch circuit works.  It’s time to capture it as a schematic in Upverter.  Start a new project.  Call it what you want, but I recommend something relating to a blinking LED.

Now that you have a blank schematic in front of you, let’s place the first symbol.  That will be our 555 timer chip.  Open the parts library from the toolbar and enter 555 into the search field.