The turnstile system continually calculates the number of people who have entered the theme park and the number of people leaving. This is to ensure that the total never exceeds the legal limit.

A Technology pupil has devised a simple model to test his/her programming. The maximum number of people allowed through the entrance for the test run is ten. The program must calculate those entering the park and balance it with those leaving the park. The total number of those in the park must not exceed ten.

The sequence of events are as follows;
The system is switched on.
The total of people in the park is set at 0.
input 1 and 2 are continually checked.
If input 1 detects a person entering the park then 1 is added to the total.
If input 2 detects a person leaving the park 1 is subtracted from the total.
If the total number of people in the park reaches 10 a solenoid locks the entrance turnstile (this stops more people entering the park)

Write flow chart to represent the programmed sequence of events. Use the following the process / systems boxes shown below.

DRAW YOUR FLOW CHART HERE

NOTES HERE

Another Technology student has devised a flow chart for the model of the theme entrance and exit. Carefully study each stage of the flow chart and consider possible improvements.

Explain two possible faults/problems with the flow chart.

Explain / describe three possible improvements / additions to the flow chart.

POSSIBLE ANSWERS

Explain / describe three ways in which the flow chart could be improved.

1. The flow chart will stop completely when there are ten or more people in the theme park. It does not continue to check to determine if more people are leaving and allow more to enter.

2. There is no manual override to the system. There may be a need for a supervisor to override the system. For example, if the park is full and there is an accident there will be a need to allow paramedics through the entrance turnstile. The present flow chart simply locks the entrance.

Explain / describe two possible faults / problems with the flow chart.
1. Add a loop to the entire flow chart so that it continually works and checks inputs and especially outputs. The example flow chart simply locks the entrance turnstile and then stops running. A loop would ensure that the program continually checks for people leaving the theme park and allows a subsequent number to enter.

2. Another subroutine needs to be added. This could be called SOLENOID OFF. Once the number of people in the park drops to below ten the entrance should start to operate again. The solenoid needs releasing so that the turnstile will start working again.

3. A new output could be added. A display that shows the total number of people in the park. This would allow the supervisors to see how many people they are dealing with. Also, in the event of an emergency the emergency services could be told the total people in the park, without delay.