Loadsa buttons!


Cycling aimlessly around Bangkok, I came across this street side stall (more of a table actually):

I stopped to see what was on offer and came across this old NEC DCR-60-1/780060…

… and all of the buttons reminded me of my friend Pavel’s Pocket Operator (by Teenage Engineering) musical gizmo, and thought that once gutted and innards reassembled, it could be used to make a sequencing musical beat doodad…

Continue reading Loadsa buttons!

Clock, Step and Hold logic


Following on from Sequence Dancing – Schmitt_trigger_NAND_implementation, and the number of issues with that schematic (from CMOS 4017 Based 8 Step Sequencer)…


Basically, the HOLD function of the schematic above does not work:

  1. An inverted (inverted by the HOLD circuit debouncing Schmitt trigger – see below) active low button press to the HOLD control (i,e, where the input to the circuit above is active high),  does not hold, but, rather, enables the clock. The active low HOLD button press is inverted by the Schmitt trigger NAND gate (see schematic below), providing an active high HOLD input to the schematic above. However, this actually enables the clock, rather than holding it.
  2. A positive edge is created when the HOLD is released, thereby advancing the clock asynchronously
  3. If the active low button press is passed through an additional inverter, so that the input to the circuit above is now active low, then the action of pressing hold gives a rising edge clock, thereby holding on the subsequent step, rather than the current step..

Continue reading Clock, Step and Hold logic