8 note Step Sequencer

This is a synth that produces squarewaves in different frequencies. You can use it to make a pattern of maximum 8 notes.

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The 8 note Step Sequencer is a synth with a square wave oscillator. You can use the synth to create a sequence of 8 notes or less. You will also be able to modify the tempo (speed) of the sequence. I'm using 2 555-timers and a decade counter for this project.


I've been thinking to make a new synthesizer for my music production. And I knew I needed something that would be able to repeat itself over and over again in a loop. The loop shouldn't be very long, 8 notes is good for me. I also knew that I wanted a square-wave sound on the instrument. The Synthesizer has to be able to change tempo of the loop and change the frequency of the notes. The frequency range has to be quite wide, hopefully from 60Hz to 20KHz. You should also be able to turn off the notes you don't want. It would also be nice if I can add some LED's to indicate what note is currently playing in the loop, so the LED would turn on at the same time as the note is playing.


My solution to the problem is that I will be using 2 555-timers and 1 Decade Counter. One of the 555-timers will be used in a-stable-mode to send signals to the Decade Counter. It will tell the Decade Counter when to change note. This is where I will use a potentiometre to change the tempo of the loop. The Decade Counter will then send a signal from one of it's outputs to the second 555-timer. The second 555-timer will then produce the square-wave. But before the signal has reached the oscillator it is passed through a switch and a potentiometre. The potentiometre determines the frequency of the square-wave and the switch controls whether the note is played or not. Because there are 10 putputs and I only need 8 notes I'll have to connect the output pin 9 on the Decade Counter to the reset pin on the Decade Counter. This way, every time pin 9 is high the loop will go back to note 1 (output pin 1).

Step sequencer (8 notes).sch

Schematic for Eagle.

sch - 548.56 kB - 03/15/2016 at 18:02


  • 1 × 9V Battery The powersupply
  • 8 × 10Kohm Potentiometer (linear) Potentiometers for the 8 different notes/frequencies
  • 9 × Switch Simple on/off switch
  • 9 × 10Kohm Resistor The resistor for one of the 555-timers
  • 1 × Electrolytic Capacitor (100µF) The capacitor for one of the 555-timers

View all 16 components

  • I ran into a problem...

    Mathias Sundgren04/21/2016 at 20:06 0 comments

    Hey guys!

    I had two weeks of holiday so that's why I haven't updated the project for some time. But I'm back now and during the holidays I found a simple multi-meter that will come in handy and I've used it quite a lot now. When I found it the battery connector was completely rusty so I had to replace that first.

    Don't get mad at me for not having a multi-meter before, I've only been doing this hobby for about three years now and I just didn't feel the need to get one before.

    Thanks to my multi-meter I found a few smaller problems so that's good.

    Never the less, as I came back from my semester I immediately started building and finishing my project. I'm almost done, all I have left is the LED's and the Stereo-jack to solder on to it. I did some testing and everything seemed fine until after I soldered the potentiometers. The current flows thru all of the potentiometers and in to the 555-timer but the current can also flow the other way, thru one potentiometer and back thru another potentiometer. So the only thing I'm getting is one single note that goes on and off and not eight. I believe I can fix this problem with some diodes. You might think that "oh but that's because you haven't put the LED's on"! I don't think that soldering the LED's will solve the problem since the current is divided before the LED's. I hope you understand, if not then you might want to look at my schematic.

    Soon I'll put a video on this log and show you the problem. I will also update the schematic.

    See you soon ;)

  • Making the enclosure

    Mathias Sundgren03/29/2016 at 21:46 0 comments


    I would like to make the enclosure in plexiglass in that way you will be able to see all the electronics inside. I'm aslo gonna leave it open because it will be easyer to fix and change things if I mess up.

    Making the enclosure:

    So I got this piece of plexiglass and now I just need to mark where I'm going to put the holes and drill.

    After the drilling is don I bent it! That means I need to make a plexiglass bender! To make a plexiglass bender you need 3pc of wood, 1 aluminum U-shaped strip, 1 nichrome wire (you can also use a hot air gun) and 2 hinges. But I'm not goning go into how to make a plexiglass bender in this project.

    Ok! So now I've finnished making my plexiglass-bender and I bent my piece of plexi already! It's a clean bend as you can see (90°

    I forgot to take a picture of the second bend. The second bend didn't go so well because I went to fast and the plexiglass started to crack in the corner but for me it's not a problem.

  • Testing the different parts for the synth on Breadboard

    Mathias Sundgren03/17/2016 at 11:17 0 comments

    Breadboard test

    I started experimenting on the breadboard. I tried different capacitors for the 555-timers and picked the ones that suited my project. When I was testing the synth I didn't use all the potentiometers, LED's and transistors. I only used 2 potentiometers, 2 LED's and 4 NPN transistors because I didn't have enough space so I could only hear two notes, witch makes it harder to choose the right capacitors for the IC's. Why? Well, because I can't tell how fast the loop will run at when I connect all the components so I can hear all the notes one after the other. The combination of the potentiometer and the capacitor affects the speed of the loop. I hope you understand, if not ask a question in the comments!

    After I made the Synthezeiser I made th schematic.

    I came to the conclusion that a small capacitor should be used for the sound-producing 555-timer and that a bigger electrolytic capacitor is better for the speed controlling 555-timer

    Here is the full breadboard test online ( with 8 notes:

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