Arduino base parking system - Simple Arduino Based Automated Parking Lot System - page 43

read_gates() function
This function lifts up and down either the entrance or exit arm gates. There are three
conditions to determine the state of each gate. For the entrance gate, the three condition are
:
1. If there is a car in front of input gate and there is a vacant slot in the parking lot, the
entrance arm gate should be lifted up.
2. The entrance arm gate is raised until its related up limit switch is activated. Then the
related motor is turned off. After a specific time ( timing function ), the motor is turned
on to bring the entrance arm gate down.
3. The motor is being moved down until the related limit switch is activated. Then the
motor is turned off.
There is a similar process for exit arm gate, but this process is started when the operator
depresses the paid key.