I need help to modify my car parking circuit. As you all might know about this assignment, there are two opt sencors one activating inputs of a Decade Up/down counter and counting up to 99 cars and the other sencor for each car leaving counting down. I deployed 2 x 74LS192 counters cascading and outputs are connected to 2 x 7-segments through 74LS47 BCD decoders. The problem is how to connect the same circuit to count down. Can anyone help me? Thanks in advance for every kind of tips and advice.

 

U1 has no inputs to let it count. Incoming cars have to produce a count pulse on pin 5, outgoing on pin 4 for the circuit to function. Read the data sheet.

 

To make it count up you need to apply a positive pulse on the CPu pin (5) and to count down you need to apply a positive pulse on the CPd pin (4). How you are going to do it depends on what sensors you have. Also, you have to connect the TCd pin (13) on the CPd pin of the next stage.

 

This can be achieved by using a pair of LDR sensors, wired up with two monostable multivibrators(IC 555) each for an LDR. I've made a people counter on the same grounds.