experiments
Interlock
An NE555-timer and D-flip-flop-based 4-way traffic signal controller, verified in Proteus simulation and on physical hardware.
all (timer period, road sequencing, hardware confirmation)
Verification checklist items passed
16/16, 0 mismatches
Boolean equations matching truth table (programmatic cross-check, all 16 states)
0 violations
No-double-green safety property (programmatic check, all 16 states)
A 4-way traffic signal controller built entirely from discrete digital logic: an NE555 astable timer providing a ~1Hz clock, a 4-bit D-flip-flop counter cycling through 16 states, and combinational logic decoding those states into 12 LED outputs (red/yellow/green per road). A full cycle takes 16 seconds (4 seconds per road: 3s green + 1s yellow). Verified both in Proteus simulation and on a physical breadboard/LED prototype, plus a programmatic cross-check of every simplified Boolean equation against the truth table (0 mismatches across all 16 states) and of the no-double-green safety property (0 violations). Includes a timed live-demo script (DEMO.md).