problem 1: Modify the state diagram branching conditions in the diagrams shown below as required to make sure the sum and exclusion rules are obeyed in each case. You can add a holding conditions or change branch codes as desired.

problem 2: A vending machine must SELL an item if 30 cents is input. The machine has a coin sensor which can detect nickels, dimes and quarters and reject everything else. No change is given (that is, if two quarters are input, simply asserts SELL and keep the 50 cents). Sketch a state diagram to assert SELL when sufficient coinage has been inserted.

problem 3: Make a state diagram for a machine which can control a 4-button digital combination lock mechanism, unlocking only if the series B0-B3-B1 is detected.

problem 4: Sketch a circuit for the state machines illustrated below.

problem 5: Assign state codes to the state diagrams below, by using unit-distance coding and/or matching state codes to outputs.