course assignment

I have started a PLC course aand I am having some problems getting into it, eg; An assignment I was given the other day has me a bit bemused, and I am looking for some guidance on how to tackle it.
I am not looking for an "easy fix" for this as I wish to progress onto the next level on my own. The assignment is :-
Car parking program.
An office building has a private car park. When a car approaches the ENTRANCE barrier it only allows entry if there are spaces availiable, otherwis it remains closed.
On leaving the car park the EXIT barrier increases the number of availiable spaces by one.
If a car tries to leave the car park via the ENTRANCE the barrier will not raise. Similary if a car tries to enter using the EXIT the barrier will not raise. The barriers , when raised, are timed to allow the car to pas under safely.

The maximum number of spaces is 6.

There is : an entance barrier.
an exit barrier.
an entrance sensor.
an exit sensor.
I have a general idea of how to do this useing, timers, UP/DOWN counters and COMPARITORS.

Any help would be welcome as I am falling behind with my studies

Thank you.

IAN A MANFORD.

I am looking for some guidance on how to tackle it.

Click to expand...

You say you have a general idea of how to proceed.

1. Take that idea with you and go to the PLC lab or to the simulator.

2. Turn the idea into ladder logic and download the program to the PLC.

3. Test it out.

4. If it doesn't work as you expected, figure out what went wrong.

5. Make necessary modifications and try again.

6. Repeat as necessary.

Ian

Follow what Steve says in his reply as that is the logical way of tackling this little problem.

If you spent some time searching this forum you probably came to the conclusion that students do not get any help unless they are seen to be putting some effort into their assignments themselves. That said, I an not putting you into the lazy catagory just yet, I see from your profile you are a mature student, that in itself says quite a bit, as most mature students are learning new skills because they want to, not because they have to.

Now to your assignment, as you probably know this is a fairly (very) easy exercise in the use of counters and timers, which you state you have an idea of how to use. Give it a go Ian, if you get stuck or are not sure of anything then post what you have written and plenty of help will be forth coming from the regulars here.

To help us help you, let us know what PLC and software you will be using.

One other point - you will get more replies if you post your questions in the 'live question and answers forum', rather than here, as this is an area for us to practice posting.

Paul