diymakeaway

Overview

8-step sequencer concept

The Clock

Because we need to set the speed our sequencer we use a simple oscillator using one NAND gate of the Schmitt trigger (CMOS 4093). And because its nice to see something there is a little LED, kind of a bpm light. For a suitable range of clock speeds, we have chosen a large capacitor (4.7 μF) and a logarithmic potentiometer (1 MΩ b), but feel free to play around and find some better combinations for yourself. A single clock can also be used to drive several sequencers, so u can have all the instruments to play together.

The Sequencer

The key part is of course the sequencer. Its a single chip (CMOS 4022), a so called counter. As the description already tells you, this little IC can count, this one can count up to 8, which is great to make music with and get a decent beat. There is an input on pin14, where u can connect the clock. And there is 8 outputs which are switched through at every step (when the clock input is signaling), one by one up to 8 and then it start from the first one again. Connect all the individual outputs to the left side of an IC socket (16 pin), and then mount for example a little dip switch with 8 knobs on the socket to start with. After the socket all the output lines can be mixed together using diodes (you can also use LEDs to get some nice visual effects of the step, but be careful of the larger voltage drop!). The resistor at the end is just there to guarante a current flow even if there is no instrument attached, so the LEDs still light up. Instead of the dip switch you can now try to add other electronic components to connect the individual steps. Try different resistors or LEDs and capacitors. The effect is even greater when you use a seperate tone generatoras described below.

The Tone Generator

The most simple way to create a tone generator is to use the spare NAND gates from the clock (CMOS 4093). To do this use the output of the sequencer to connect to one of the inputs of the NAND gate, eg. pin12. To have a more interesting oscillator use a smaller capacitor and a light sensor (light dependant resistor, LDR) to have some smooth interactivity. Now just add this to your amp or add a little piezo speaker and listen.
More interesting is to use another chip as a tone generator, because this gives you much more options to tweak the it, you dont want that your clock gets tweaked at the same time. You can now connect the sequencer signal to different positions in your circuit. For example you can use it to power it, so dont connect it to a battery but only to the sequencer. Make sure you always connect all GND together. You can also use it to turn on and off an amp or just hack into the audio signal wherever you like.

The Glide
As it is know the sequencer gives a binary output, like on and off, 1 and 0. You can change this by adding a single capacitor (usually large ones do the trick 200 μF and above). The output signal is now smeared out and this will lead to very interesting gliding tones and weird quenching effects when the tone generator chip is about to power off.

The Movie

Fig 2. Still images from the movie „8 STEP SEQUENCER“ by dusjagr & haselbach, Swiss Mechatronic Art Society, 2007. Stop Motion animation shows how the simple sequencer described in this text is self-assembled and some sound examples thereof. Visit www.mechatronicart.ch or www.viddler.com/dusjagr/videos/ to see the movie.

Schematics
8-step_schematics_big