TOLLBOOTH
State Graph
There are 4 states represented by this state graph. S0 is the tollbooth closed. S1 is the tollbooth opening. S3 is the tollbooth open. S4 is the tollbooth closing. The state graph shows what inputs are required to move from one state to another and what outputs result in each state. Each state has 4 input variables: open switch (OS), close switch (CS), open limit (OL), and close limit (CL). Depending on which inputs are activated (or not) the arm of the tollbooth will move through the stages. Each state also has corresponding outputs: motor open (MO), motor close (MC), gate open (GO), and gate close (GC). The tollbooth will always follow this path based on the inputs.
Transition Table
Simplified Logic Expressions
Circuit Schematic
VEX
Conclusion
Dear Mrs. Zienty,
Overall this project was fairly simple, but had its issues just like any other. We began the project by building the tollbooth itself with a VEX toolkit, which ended up being an issue when we added the program to it. The gears were placed slightly too far away which resulted in gear grinding and a malfunctioning tollbooth. Then we began to decode the state graph and transition table. The graphs were confusing at first, but once we realized what would be happening in real life they became a lot simpler. After looking at the graphs and the logic expressions we made the PLD circuit on Multisim. This was not too difficult because it had the same format as some of the other projects we had done, but still resulted in the biggest headache because we didn’t realize the PIOs were not connected. Once we fixed our PLD circuit and borrowed a VEX machine we had a perfect tollbooth. This project was pretty similar to other projects we have done because it was a circuit designed to follow a pattern, but in this case the pattern was not counting numbers, it was a pattern of movement.
Throughout the Digital Electronics course I have learned a lot and actually found the class a lot more enjoyable than I had originally thought I would. This project specifically taught me that when reading schematics you can’t just look at the variables, you have to imagine what those variables represent. This project was easier than some of the ones at the beginning of the semester because I had more experience with the software and learned how to troubleshoot on my own. Next time I would organize our Multisim better and build a tighter gear system because our issues were there.
Thanks for everything,
Alison
Overall this project was fairly simple, but had its issues just like any other. We began the project by building the tollbooth itself with a VEX toolkit, which ended up being an issue when we added the program to it. The gears were placed slightly too far away which resulted in gear grinding and a malfunctioning tollbooth. Then we began to decode the state graph and transition table. The graphs were confusing at first, but once we realized what would be happening in real life they became a lot simpler. After looking at the graphs and the logic expressions we made the PLD circuit on Multisim. This was not too difficult because it had the same format as some of the other projects we had done, but still resulted in the biggest headache because we didn’t realize the PIOs were not connected. Once we fixed our PLD circuit and borrowed a VEX machine we had a perfect tollbooth. This project was pretty similar to other projects we have done because it was a circuit designed to follow a pattern, but in this case the pattern was not counting numbers, it was a pattern of movement.
Throughout the Digital Electronics course I have learned a lot and actually found the class a lot more enjoyable than I had originally thought I would. This project specifically taught me that when reading schematics you can’t just look at the variables, you have to imagine what those variables represent. This project was easier than some of the ones at the beginning of the semester because I had more experience with the software and learned how to troubleshoot on my own. Next time I would organize our Multisim better and build a tighter gear system because our issues were there.
Thanks for everything,
Alison