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Old December 1st, 2021, 01:29 PM   #16
Frost999
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Aging thread but...

Normally we would use vehicle detection loops and loop controllers (that provide dry contact output(s) for detect / non) vs. photo eyes but the control is the same.

An entrance / gate will actually require THREE loops (or PEs) to count correctly. When the car pulls up to the gate to enter, it should cover TWO loops. This way, if the car decides to back-out, we can tell by the order of detection falling out whether it goes forward (and crosses the gate's loop) or back out.

20+ years ago, you could do this (back out after pulling a ticket) and give the ticket to a buddy that had been on the lot for a week and he could use it to get out under the grace period (varies by lot as needed) without paying.

NOW; the ticket generated at the spitter (I know that's not a part of this but..) will have a flag set in it's related database if the car backs out. This identifies that the ticket may be in use for fraud; especially if someone uses it to try and get out. Most places will call it an "alarm ticket".

This has also led many larger facilities to do "LPI" every night. That's license plate inventory. This is usually done with a handheld that has the lot's parking order laid out in a framework, so that each plate can be entered (just that data / space data is established) each night. If a customer tries to pass off an alarm ticket, it is seen at the exit and then the car will looked up on LPI to see it's real time spent on the lot. You actually can be charged a bit more as well, as most lots will bill hourly up to a daily max. The LPI is done at night, so they will bill it as full days at both ends.

To add to this... all entrances and exits SHOULD have at least two loops. That way, unintended entries and exits will still increment or decrement the lot count in order to maintain integrity. Decades ago, just out of college, I had a large deck at an airport that consistently "lost count". Video revealed cars driving up the center exit ramp the WRONG WAY (!!) We needed extra loops here (used singles on that exit ramp coming off of each floor) and then we were able to maintain counts/floor.

People do crazy things when they are driving in "unfamiliar" places, and they also seem to have very few scruples over trying to "steal time" that they actually spent on the lot.
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Old December 1st, 2021, 01:56 PM   #17
drbitboy
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Quote:
Originally Posted by Frost999 View Post
Aging thread but...

Welcome to the forum!

Wow, fascinating stuff. No, I am not being sarcastic; the evening course instructor for OP would do well to have you as a guest lecturer for a 10- or 20-minute zoom to talk about this stuff.

Learning to code up a few Start/Stop or State/Fault patterns is not that complex; the student should either get it after a few weeks or move on to something else.

But learning why a certain design pattern is useful, and where it applies, and thinking through how a process normally works, and how it might work in the abnormal case, is far more valuable.

Those overlapping loops were what I was looking for; I think it's analogous to quadrature in motion encoders.

Thanks!
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Old December 2nd, 2021, 09:31 AM   #18
Frost999
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.... and how it might work in the abnormal case, is far more valuable.

Those overlapping loops were what I was looking for; I think it's analogous to quadrature in motion encoders.

Thanks!

Yeah that's right.. To add a little more to above, most gates (used on paid lots) in the last 20ish years will utilize nylon hardware to protect the gate's arm-drive in the event that it is hit. The hardware will give and the arm will drop off. If this happens at any entrance or exit, you can expect un-authorized (ie; they didn't pay) exits, regardless of it's orientation (as entry or exit). Because of this, we really need a minimum of 2 loops everywhere you can come or go to maintain the integrity of the lot count.

Every major airport that I know of makes more money off of parking than most of the airlines pay in gate-lease fees (all) combined. Given that this is their main stream of revenue, they tend to try and tightly control it.
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