So when I first started messing with electronics stuff I decided to try to understand things starting with the simplest components and working up from there. I found a binary counter IC and wired together something to convert its binary counting to sequential counting by using transistors as digital logic gates. I cheated a little bit and used some packaged IC NOR gates but still this is on a pretty fundamental level of digital logic.
The battery connected to the voltage regulator on the left goes to a 555 timer that is just pulsing a signal to the binary counter. The battery also powers the red LEDs and if I remember correctly the other battery is to power the yellow LEDs because the voltage drop through the 555 and a red LED didn’t leave me with enough for another LED at the same time with the way it was wired. The outputs directly from the counter are displayed on the yellow LEDs and the same outputs pass through all the digital logic crap and light up the red LEDs sequentially.
Using these larger discrete components makes you realize how much goes into these small chips we have even for very simple functionality. Just the 555 timer itself could be made with the same transistors and resistors I used for the logic parts here. Take a look at this kit where you can do just that http://www.evilmadscientist.com/2013/555-kit/ And here’s a video of the counter in action. There’s an episode of Futurama playing in the background providing the somewhat epic commentary.