I am currently working on designing a t-bird tail light control unit. The requirements for the system are presented on the table below: enter image description here

I have a full circuit made which I'll provide in the screenshot below:enter image description here

So far, my circuit works for all of the scenarios EXCEPT for when the left/right lights are supposed to flash while the other set of lights is supposed to be on. What happens is when I OR the B input with the output of the AND gates from the state machine, the lights that are supposed to flash do not since B is feeding the OR gate a constant 1, however the other set of lights that are supposed to constantly stay on do stay on as they should. I have been struggling trying to solve my problem here but have not been able to so I came on here for ideas. Any help will be appreciated. (The circuit works for all of the scenarios except the one mentioned above.)

  • \$\begingroup\$ What is a "t-bird tail light"? \$\endgroup\$
    – Hearth
    Commented Feb 5, 2019 at 0:05
  • 2
    \$\begingroup\$ @Hearth Tail lights for a Ford Thunderbird car. This is a surprisingly standard lab/homework problem in digital logic and state machines. The Ford Mustang revived the "sequential taillights" in 2010. \$\endgroup\$
    – user71659
    Commented Feb 5, 2019 at 0:49
  • 2
    \$\begingroup\$ The original Ford Mustang and Mercury Cougar has sequential turn signal lights. The timing was done with a DC motor turning an shaft with machined three cams, each operating a microswitch to control one of the three lights. \$\endgroup\$
    – AnalogKid
    Commented Mar 29, 2022 at 4:37

1 Answer 1


Your logic is Flash OR instead of L/R XOR Flash. i.e. L/R Flash out= (L/R XOR M ) AND Flash in

Solid On = L/R AND not M

That is why it fails.


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