Created by
Created March 10, 2015
Last modified March 10, 2015
Tags 7555   ac_dc   arduino   mux   punk   step-sequencer   teensy  


DIY step sequencer built with microcontroller, analog mux and 7555 astable oscillator.


basic starting circuit for a monophonic step sequencer. the multiplexor(mux) is driven by the teensy. one must run code on the teensy to cause the mux to change channels. The potentiometers (pots) are connected to the first 8 channels (0-7). Binary words (nibbles) set the mux to connect one pot at at time to the voltage control pin of the 7555 astable oscillator circuit (oscillator).

The output of 7555 can drive a passive speaker or be connected to a mixer or amp. It would be be best to add an output high pass and some resistance when connecting to headphones, in case the signal is too loud.

Fun modifications:
1. add a lowpass to the line between the sig pin of the mux and the control pin (5) of the oscillator. use a button to make/break the connection to this low pass. 2. add a gate function to the code driving the mux and set the Teensy digital pin wired to pin4 on the oscillator Low to stop the oscillator from sounding. you can now add rests to your step sequencer, or short silences between each of the 8 notes. 3. if you have 8 more pots, connect them to the remaining mux channels 9-15 and modify the code to count all 16 steps.


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