10. Automatic Gearbox

This circuit is on Circuitverse: https://circuitverse.org/users/151941/projects/automatic-gearbox

This is a FSM circuit

This circuit simulates an automatic gearbox found in most cars in a simplified manner. The two inputs used for this are a gas and shifter input, which indicates a 1 for being on the throttle, 0 for not, and 1 for being in drive, 0 for being in park. In this sense the FSM will move forward while on the gas, backwards while off it, and will remain in state 0 or park when not in drive. S0 as mentioned is the reset and represents park, while S1-S6 represent the gears 1-6 in the car. I decided to stick to 6 gears even though a lot of cars nowadays have more than 6 gears with an automatic transmission to stay relatively simple. So with this being a Moore machine, the outputs entirely depend on the state alone, so each state has 1 gear output on or none at all if it is in park. Below are the equations used in this circuit along with the work to accompany it. The shifter will always put the car back into park as it does somewhat in real life.

Equations:(Inputs are labelled G and S for gas and shifter)

A+=BCGS+AGS+ACS+ABS

B+=B'CGS+BCG'S+BC'GS+AB'C'G'S

C+=A'C'S+A'B'G'S+ABG'S+AB'C'S

Gear 1=A'B'C

Gear 2=A'BC'

Gear 3=BC

Gear 4=AB'C'

Gear 5=AC

Gear 6=AB

Below is the work by hand to create this FSM: