Lesson 4: Creating a Sequence

In this lesson we introduce the last building block, the 4017 IC and utilize the clock circuit from lesson 2 to drive the sequence

See the recording for the note about the broken audio jack. If yours did not break then don’t worry about this

Zoom Recording of the Lecture

zoom recording



No new components are introduced this week but if you want to learn about how the 4017 counter chip works then first read this article on flip flops which are the building blocks of a counter.

  1. What is a flip flop

The 4017 IC

The 4017 IC is a decade counter. This means that it counts sequentially from 1-10 and outputs a logic HIGH at a specified output pin (0-9). We will use this chip for the “sequencing” aspect of the project which ties together the circuits from the last two lessons.

counter gif

This gif provides a nice visual of how the counter works. Note that this chip is driven by a clock (we will use the clock circuit we built from lesson 2!)


The 4017 has 16 pins which may seem like a lot but this chip is actually very straightforward to use.
As we did with the 555 IC let’s distinguish the significant pins from the insignificant pins so that we can understand how the chip works.

Insignificant Pins

Again by insignificant, I mean pins that don’t require too much thinking

Significant Pins

That is all 16 pins. If you see a strange output (LEDs flickering or not counting correctly) the clock output may be noisy. Placing the 0.1uF capacitor on 555 pin 5 to ground should fix this. We originally used the 0.01uF capacitor for this but we had to switch it for the synthesizer circuit.

That is it for this lesson. I wanted to keep it short this week because the next lesson is the last lesson and we will be connecting this counter circuit to the sound synthesizer circuit (this part is a little tricky). It is important that both these circuits are functioning before we connect them because debugging the final circuit is very difficult, especially over zoom :).

Circuit Diagram

This diagram is kind of messy so you may want to refer to the slides for a sequential assembly of the circuit counter