Parking Sensors

I was thinking an unemployed car thief, but that would violate requirement #3.

If you have a separate entrance and exit for the lot (in other words, in one way and out the other) you might employ an optical beam that would trigger when a car enters the lot and then triggers when a car leaves. You could use a inductance loop, too. If the incoming sensor increments a counter, the outgoing counter would decrement that counter. As long as the counter is non-zero you have a car in the lot.

Still I question how reliable that could be since there are 1001 things that can spoof it or just go wrong.

I think that is why there are still parking lot attendants. College kids will work for food. ;-)

Yes optics isn't reliable in a public outdoor park like this one

Hello Smart_Viral

Which "Park" do you mean?

1. Car park - plain, on the street
2. Car park with 'metered space' on street
   
3. Car park in enclosed space
4. Car park in enclosed space with gate
5. Car park in enclosed space with small entry
6. Car Park - "Parking Building"

Advise with Specifics please, because there are different methods, dependent on "Parking Type".

Kind Regards....

a public outdoor park like this one

Hello again Smart_Viral

Your diagram is not clear.

1. Is it only a part of a larger diagram? If so, please give full diagram in your reply post, by left click on your uploaded full diagram, then dragging the corner of the full diagram in your text Editor box, and expanding it, so it is not automatically super-compressed by CR4 Forum Software, thanks..For full instructions please refer: http://cr4.globalspec.com/comment/161924
2. Are the shadowy 'vertical parts' meant to show a single car?
3. The long 'curved' almost enclosing those 'shadows' part, is that a raised concrete edging or berm, or is it a painted line or marking on concrete surface?
4. Is the 'round dot' a 'roundabout', around which cars may turn, using the central 'island dot' as a 'pivot point'?
5. If an outdoor carpark, is there Security lighting?
6. Is the need for establishing car presence one of Security?
7. Is the need for establishing car presence one of 'charging for metered space'?
8. Please give approximate dimensions for the 'shadow' area - a single 'shadow' please.
9. Is the carpark to be available for use 24/7 = day and night?
10. If each 'shadow' represents a car, and the long 'curved' part is a raised concrete berm, I do not see how a driver could safely enter, park, and exit, without accident, unless the car arrives and leaves vertically.

Appreciate

Kind Regards....

Optical scan using camera and software to differntiate tarmac and objects on tarmac. I worked for a company that built cameras for use inside the glass melting furnaces used for making window glass. Our electronics detected the slight variation in gradation created by the edge of the molten glass flowing across the molten zinc. today's digtial video processing is much more sophisticated.

You would need to have a "zero" reference of an completely empty parking lot. If in snow country you probably need two such references. If parking lot is undulating you may need to tweak the soft ware to differntiate betwene a car and a water puddle. Some kind of spectral filter migh tbe handy.

I recall our chief engineer grumbling that we could find the edge of molten glass on molten zinc but we could not create a detector to tell if a 50 ton box car was sitting on the track in front of the sensor. That was long ago. Today bar code readers and optical scanners work perfectly doign the job in train shunt yards.

we built a optical inspection system to check the location and orientation of brackets on a plastic fuel tank, a few weeks later, the customer came back saying that they had reliability problems.

It was found that they changed the plastic brackets from White on a black tank to black brackets on the black tank DOH!!!

then the tanks were +/- 2" (~50mm) accuracy in positioning (and size/length)

The cheapest way that meets your specifications to detect if there is a car in the park or not is probably visually. Get your lazy arse up out of the chair and go look. If that is not practical (your specifications are rather vague), a camera with a birds eye view would likely be a good solution.

In the US, we park on driveways, and drive on parkways.

Simply take a long string, start at your booth and lay it in a looping pattern covering all the possible locations a parked tire may be.

At the end of the day you can pull the string-if you wind all string in to the other end you have no cars.

Obviously this requires the extra work of setting up each morning, so you can try option 2- Instead of pulling the string and winding it up, simply start at one end (probably the booth end) and follow the string. If you make it all the way to the other end without bumping into a car, your lot is probably empty, and you never need to reset the string.

If you want to go digital, the same can be done with a rubber air hose, except you start and finish at the booth, this way both ends are in the booth.

Get a big green balloon. Blow up and write the word EMPTY on it. Deflate and attach to the hose. At end of day blow (hard) into the hose, see if the balloon inflates and the word EMPTY appears.

I have more ideas, but I cannot share them for free.

The cheapest sensor consists of a Mk.1 eyeball and a brain.

The cheapest(and Best) sensor consists of a Mk.1 eyeball and a brain.

Agree 100%

MM

the purpose of the system is to detect cars positions not counting. An overhead cameras with image processing will be a great idea.

thank you everybody

OH SHURE! Change the specification at the last minute. Do you work for the government?

What about trained guard dogs (Dobermans are pretty smart)? They work for food and may be cheaper than college students.

I've known some pretty cheap college students!

In actual fact the cheapest sensor would be a pigeon, as they always find a car, marking it to let others know the pigeon got there first.

Kind Regards....

Camera (gives detailed information, but wiring may need protection, and needs human monitoring).

Optical interrupters if you want an automatic record of what was where at what time (can be shared between parking bays if that's what you want, also very cheap and unobtrusive; can be spoofed by bags of cement, though)

Acoustic sensors

Once you can specify your specific information needs and budget a decision becomes possible

A magnetic sensor may be possible (it doesn't suffer from the problems optics suffer from but does have other issues). Of course you probably don't want to have a wired sensor system that requires you to bury wiring to each car park space (unless the car park has yet to be built), which leads back to a remote optical system.

Optical may be expensive, but so are site works for fixed wiring. Other options include sensors with transmitters and energy harvesting power supplies but I think that is beyond the scope of this application, although you have indicated previously that you are a power engineering undergraduate student. This wouldn't happen to be your graduation project would it?

I would suggest looking on the internet at a number of technologies to see which may be the most suitable, and of course at what others in the industry have done to accomplish similar tasks to the one you are researching. This should give you some more ideas. Hey, you may not come up with the ideal solution but that takes experience and practice. I mean we could give you the answers but you wouldn't really learn anything.

No, this is not a graduation project

I'm helping someone to design a parking system to guide drivers in large parks using tickets or digital traffic signs.

In a small system magnetic sensors will be useful but in a large one image processing becomes more economic with less wires and installations.

Try a paintball gun, it works great, if you don't hear any metallic clunks, then there is no cars....