17Aug2025, Journal Entry

• So, the challenge for the coming days is to start building a simulation in LTspice demonstrating how a Schmitt trigger, as the active element, can be used to fabricate a finite state machine. Since the realm of physical systems hinges on potentials and forces rather than flows, this suggests a MOSFET-based, voltage-driven, Schmitt trigger circuit rather than a BJT-based, current-driven, circuit.

• I have never seen a finite state machine assembled using Schmitt trigger circuitry as its active elements. So, this simulation will be an exploration into uncharted territory.

• In practice essentially, universally, all finite state machines are assembled using registers (flip-flops) to encode states. With additional combinational logic circuitry used to capture the state machine’s corresponding rule set. Stepping through accessible configurations being initiated by an external clock source.

• At the molecular level, there are no obvious way to instantiate bi-stable (flip-flops). Nor ways to assemble freestanding molecular arrangements corresponding to a companion system of combinational logic.

• Here the Schmidt trigger arrangement serendipitously gets us around the above challenge. Rather than combinational logic to couple the various states together, one can use instead the parametric coupling captured in the ratio of the resistor values R3, R7. See accompanying schematic.

• This is where things get really interesting. Suppose our Schmitt trigger based finite state machine is built using a combination of circuit elements and mechanical elements. Then that resistor ratio can be instantiated as a mechanical flexing of the state machines physical body itself.

• So, first step is to SPICE simulate a finite state machine using the Schmitt trigger as its active element. Then extend that SPICE simulation to include additional flexing mechanical elements.