Car Wash PLC

Hi,
I am a student in the UK studying for my HNC in Engineering, part of the course are PLC lectures, as i have not encountered them before i am struggaling. The assignment we have been set is to design a CAR WASH plc system, taking into concideration what sensors to use, which PLC what safety percautions/procedures can be used ect. I was hopeing someone could help me and give me a few ideas or send me some information or even direct me to some where that would give me an idea

[email protected]

This site is an excellent place to learn about PLCs. Study the tutorial. When you encounter something you don't understand, post a question about it.

As to your specific assignment. Take a field trip to the nearest automated car wash. Watch it operate. Take notes about the sequence of operations. Try to figure out how it knows when to turn on the water, soap, brushes, etc. Does it turn on the water when it detects that the car is in the proper position? The device that detects the car position is a sensor.

Once you've reached an understanding of the sequence, play a little game. Watch a car go through the system and mentally tell the car wash what to do next, just a second or two before it does it automatically. For example, when it reaches the proper position, say "Vehicle is in position. Turn on the water". When you find that you can anticipate what the car wash is going to do next, you're ready to transfer your understanding of the system to the PLC.

Wet behind the ears?

The first step will be to create a list of all the I/O the system will need

Possibly the easiest way to come up with such a list is to go out, with a buddy, and wash a car.

Blindfolded.

Take careful notes (or rather, have your buddy do it). If you need to know where something is (such as the front of the car), you'll need some kind of sensor to detect it. Prox switch, photoeye, limit switch - it probably doesn't matter (for the exercise) as long as the front is detected.

If you turn off the water, you'll need something that will do that.

Record everything that your buddy tells you to do - that will eventually be the basis of your program.

Afterwards, visit a car wash. See what steps it takes. The one difference between what you did and what the machine does is that the car moves while the equipment stays still (although I think I've seen one where the hose does rotate around the parked car). Ask (yourself) lots of questions:

• "Does the chain start-and-stop, or does it move continuously?"
• If it starts-and-stops, what triggers that start? What triggers the stop"
• Are there options (No Wax/Wax/Pricy Wax)? How are those "told" to the machine?
• How would you do it blindfolded?

If you are wondering why 'blindfolded', read Terry Woods post on just how a PLC "thinks" HERE .

Carwash

No, the first step is to contact the PLC vendors as all of them give a carwash or carpark as a standard program example when selling a programming package.

Correct me if I am wrong but in the UK every car wash I have used, the car stays parked and the machinery moves around the car.
You drive the car up to a plate stuck up from the floor and then the brushes and water spring into action coming across the car washing and squirting as it goes by.
(It gives you a weird sense that you are moving but you are not)Is it done different in the USA?

About a year ago I ripped out an old carwash system that was controlled by a Toshiba plc. I have always meant to upload the program within, just to have a look.

Another point to this program (at least in the UK) There are different tarrifs for different washes. starting at: basic wash, (cold water and revolving brushes) through to super duper hot wash, hot wax blow dry. These are usually about 5 separate programs costing 2 pounds to 5 pounds.

If you were programming this plc you would have to have different tarriffs too.

Stevecase,

I hope you had your tongue firmly planted in your cheek when you posted your response, else I'd be forced to conclude that you think that the primary goal of a student in an HNC course is to achieve a good grade and actually learning something is of secondary importance.

Goody,

Here in the USA, the vehicle gets pulled through the carwash and the water jets, scrubbers, brushes, etc spring into action as the vehicle goes by.

Originally posted by Goody
Correct me if I am wrong but in the UK every car wash I have used, the car stays parked and the machinery moves around the car.

Click to expand...

In the US, this is known as a rollover system.

Originally posted by Allen Nelson
"Does the chain start-and-stop, or does it move continuously?"

Click to expand...

Allen is referring to what is known in the US as a tunnel system. It commonly is controlled by a shift register with all options tracked by the chain that pulls (or pushes) the car through the tunnel.

A third type in the US is the bay system in which the car is parked in a bay and the customer does the wash himself.

Unquestionably...

The first step is to go to your local store and buy a pencil, pad of paper and a case of beer.

Then, and only then, should you venture to find a REAL operating Car Wash.

Set yourself down at the infeed-end and watch very carefully to see what is going on. Take a lot of notes... you should take more notes than sips of beer. Watch what the operator does to get the system going.

After you think you have everything you can get from that end, walk around to the outfeed-end (don't forget your beer). Again, take copious notes.

After you are satisfied that you have all of the info you can get at the outfeed-end, go back around to the infeed-end (again, don't forget your beer).

Now, here comes the critical part...

Standing at the infeed-end, chant to yourself over and over...

BE THE CAR... BE THE CAR... BE THE CAR...

Let yourself get hooked by the puller chain.

Continue chanting... BE THE CAR... BE THE CAR... BE THE CAR...

As you go through the process, take as many notes as you can before you get too much soap in your eyes... don't forget the beer. Did I mention that you should be wearing a wetsuit? Pay particular attention to any sensors you might run into along the way.

When you get down to the blower, be careful not to lose your notes.

When you leave the Car Wash, go back to where you left your beer and organize your notes into Infeed-Spray-Wash-Rinse/Wax-Dry-Outfeed.

Now you should know all of the output devices and the input devices and how they interact to complete the process.

You can quit chanting now. Here's a new chant...

BE THE COMPUTER... BE THE COMPUTER... BE THE COMPUTER...

Now, as Allen indicated, try to figure out how you, AS THE COMPUTER, can accomplish what you just experienced first-hand, without actually seeing what's going on (which should be easy with all that soap in your eyes).

Yes, you can have some beer while you are doing this! However, you might want to change into some dry clothes first.

Do a search for beer and "Terry Woods" comes up 90% of the time.

Then again, do any search and "Terry Woods" comes up 90% of the time.

NEVERMIND

LMAO

Great stuff Terry. I always felt that my formal education suffered because there was insufficient attention paid to the beneficial effects of beer as a dietary supplement - and that was in Milwuakee!

Lefty,

One should never ignore the benefits of Hops and Barley when it comes to seeking solutions to all-encompassing, universal type questions. All preconceived, pretentious and superficial notions (barriers) seem to fall away when seen through the bottom of a beer bottle.

The "What if..." factor takes on all kinds of new possibilities!

"Left-field", "Duality", and "Reverse Duality" type solutions become more apparent and more feasible.

The problems come in when you try to attain the same level of inspiration and enlightenment through the imbibement of various potatoe, grape and certainly, Sterno products.

BTW (By The Way), what is LMAO?

LMAO = Chuckling to such an extent that the glutimus maximus departs company with the surrounding connective tissue and decends with the gravitational pull of Earth towards Terra firma.

Sometimes I find that I need a RESET (a 2x4 laid up aginst the haid).

Now is one of those times.