We all have faced problems like entering a parking lot which haven't got any free space inside.
This counter help drivers entering a parking lot to know prior to entering whether their is vaccant space or not inside the parking lot provided the max capacity of the parking lot is displayed alongside.
This system is based in a token generation system.
There will be a laser falling on the ldr setup at the entry as well as the exit gate and when the token while being generated at the entry gate or being submitted at the exit gate(which will be transmitted wirelessly to the main counter at the entry gate) will cut the laser (here I am doing that by covering the ldr(s) with my finger) will upcount and downcount respectively hence manipulating to the total count.
[No. Of Cars Present= No. Of Upcount - No. Of Downcounts]
This can also help to block the entrance automatically through boom barrier technology if the space is filled up.
It may also help while evacuation during emergencies to help us realize that all the cars present has exited or not.
This also has applications for example in office buildings to know whether all the employees have exited or not for which only one change is enough like the token to be replced by the employee's id card which will block the ldr.
Its is a low cost module and all the components include will have a cost of Rs. 350 to Rs. 400 at max.