Parking Lot Counter Question

[Quintessence]

Hi,
I'm a new user here, and I was just wondering about how to make a counter to fit my assignment which is as follows:

Parking Lot: A parking attendant needs to keep track of vehicles entering and exiting a parking lot in order to allow a maximum of 50 vehicles to be in the lot at any given time.  Design a circuit that allows the attendant to add or subtract vehicles as they enter and exit the lot (push one button to add, push another to subtract).  Include a design where if the total number of vehicles equals 50, a flashing (1Hz, 75%DC) “Lot Full” sign that’s provided will be lit.  The attendant may not increase the number beyond 50, or decrease the number below 0.  Include numerical displays with your design.  Also, you need to keep track of the total number of vehicles that have entered the lot for the day (maximum 99).  A reset is required to start the day with 00 cars.  

I'd appreciate any input, I decided the easy way to do this would be to use the 74192 counter, but I'm not too sure how to implement it, as we haven't really discussed it in class. I'm guessing I'd also need to divide down the input frequency as well.

Thanks

[MP]

Use two sensors for the cars to go through and some gates to give you some direction. One of the sensors is going to be blocked before the other depending upon the direction of the car.  Then it is a matter of an up/down counter.

MP

[Quintessence]

I'm just trying to understand, that it needs a clock edge on every count up and count down, so I'm just wondering if i need to wire up two debonuce switches, two clocks to the appropriate frequency...but is synchonization of the clock edge and the count up count down switches needed?

[MP]

I think I would use logic gates to determine whether it was up count or down count. This being determined by which sensor comes on first.

MP

[trigger]

You can try using 74HC193, the binary up/down counter and cascade them to counter up to 50.

[prateeksikka]

HEY all of you!
can u believe me nothing is required(hardware)
for such a project but just a few LEDs and that too during the debugging of the simple software u write for it.although some hardware may be required if u wish to have automation.but if the attendant is ready to push a computer key,then that can easily increment car count in my software written in "C" and can also be decremented,at every key my software checks if the count has reached the parking place limit,if it has,then send a high at computer port which is sufficient to switch on a LED or a relay(for an alarm)HOWZ THAT? ;)
prateek

[GreekPIC]

...Design a circuit that ...