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Parking slot supervision project: 7-segment 2 digit display panel addressing

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by earckens, Sep 1, 2017.

  1. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    MODBUS:

    It can run over Ethernet and RS-485

    http://modbus.org/

    Python has a MODBUS library: http://www.lmgtfy.com/?q=modbus+for+python

    With anything writing drivers can take a long time. I tried to write a LabView driver for a motion controller and it was really hard.

    A gazillion years ago, I wrote a FORTRAN program with diver ENTRY POINTS. It was a strange beast, I used the same basic structure for all devices. e.g. Write to log; write to display; parse config line, save config parameters, set config.

    It was really, really cool. the txt file had lines and a dispatch code The main routine parsed the txt file and then moved the file pointer back one line an then the driver routine would be called and it would do the read. It may have continued to do the reads until the device changed, It would then back up the file pointer and return.

    I also wrote drivers just to optimize speed.
     
  2. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    This http://circontrol.com/solutions-for-efficient-parking/ipark/ is like WOW!

    Who needs a programmer.

    What you want is probably already done for you and then some. the license plate recognition, find your car apps, find handicapped spaces seem really, really cool. Lighting covered. So is brightness control by software.
     
    Last edited: Sep 2, 2017
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  3. earckens

    earckens Member

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    What an amazing input KeepItSimple! I will print out this thread as it will serve as a checklist for current and future projects.
    For the displays: interesting to discover there is a German company doing thses, I was not aware and I appreciate your helpful comments there. Also, luckily these displays are to be mounted inside the building, no need for IP higher then 53 I think.
    Colour, size, ..: customer does not care too much, as long as it is readable from about 10m.
    As far as the W10 pc is concerned: daily and weekly reports are require, basic calculations (just the number of free spots for the day, for the week,..). However since we collect data per slot by the 10 seconds it is possible to generate extremely detailed reports.
    R-Pi is an option I will explore for future projects, here all that is needed are 14 displays hooked by TCP/IP, power is no issue (the customer installs cat5 and power as we need). TCP/IP addressable text display panels are being made available, cost is USD175 FOB (see pictures), but since this is an all-in solution it is worth the cost for me: rather pay a bit more and save future debug headaches.
    The parking slot sensors are wireless, they communicate over 868MHz to Wireless Data Collectors with directional antennas; it is the job of the programmer to link all 7 or more WDC's together and collect all these data in a correct manner.
    UPS: very interesting observations in your post; will be included; I need to look into this more in detail and together with the programmer to find a correct concept.
    Test routines for sensors: very sensible observation; especially since they are wireless: needs to be verified and correctly implemented with the programmer.
    Web application: nice for future use; here all the customer needs is one computer graphical display with the two floors showing status for each slot; and on the left a bar with the values on the 14 displays shown. No need for sharing or client pc's.
    Labview: I will explore that route.

    This coment I do not understand:
    You would have to confirm if:
    1) Auto delete = 0 and Rollover set to <don't care> would always display a number.
    2) Is all spaces legal for power save mode. You could even reduce that to a DOT if it isn't.

    Cabling and wiring: I would prefer to use cat5 all the way; from the WDC's to the pc is a given due to the nature of the WDC hardware; and for the displays same due to the nature of what I was offered by the supplier (see pictures and comments above). And customer will do the work, so no cost issue for me.

    KeepItSimple, I want to thank you profoundly for all your comments and for the time you put inti this!
    Erik
     

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  4. dave

    Dave New Member

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  5. earckens

    earckens Member

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    Interesting! And where do I find the cost estimate for a 100 parking slots? Probably need to contact them directly.
    It is just that the customer prefers a wireless sensor solution.

    EDIT: I did send circontrol a mail with request for information.
     
    Last edited: Sep 3, 2017
  6. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    If the (WOW Sensors) are battery powered (5 yr life) wireless sensors, then every 10s makes no sense. They said 10 minutes
    Because you want to conserve power. 10s is unrealistic.

    The Wow guys said that some parking garages, the floor can't be drilled.

    I think that's exactly what the Wow! guy did. It's 868MHz to RS485 to Ethernet. Note that they put all of the low voltage DC power together like I possibly suggested. The protocal converters aren't exactly real cheap. I have a few that I haven't played with yet. So, the 868MHz gets power and data and you tie what you can together. Remember 32 Max.

    So, Ethernet allows you to expand past the 32 receiver limit. Those battery powered receivers have to also have a limit for the number of parking sensors.

    LED's require power. Low voltage power is easy to work with. Meaning PVC could likely be used even if it could be banged by a car, 120 VAC you;ll need metal and sealed. One of those displays (the 5 digit 5" one)

    In an earlier research the displays were "something else" and not what we might think of as a display. They displayed PIN numbers for a short amount of time. The documentation never says it can display a value forever. Unless it's explicit, i assume it won't.

    #1: Is displaying PIN numbers for a short time and then removing it from the display, Not display forever.
    Auto delete and Rollover are webpage parameters. Don't delete, should ignore rollover and therefore STAY forever.

    #2: 14 displays x 10 Won all of the time is 140 W/hr ---> some Kwh/month. Turning off a display would be writing spaces to it. can you write 3 spaces? or is it delete all of the numbers. It's gotcha if you don;t pay attention.

    Like I said, no car coming up the ramp, the interior display could be dark.

    Those displays that you have are controlled how? It's important.
     
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  7. earckens

    earckens Member

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    I agree 10secs is not realistic in view of battery life, indeed 10mins is more likely.

    Who are "the Wow guys"?
     
  8. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    You said you would collect parking data every 10s, but the battery powered sensor only wakes up every 10 minutes.

    I only had the time to read over one sheet from the "Wow" guys.

    The "Wow!" guys was the comprehensive solution, They had all the parts and knew how to use them. The other ones were an attempt to build based on "generic parts" that may have other specific purposes. e.f. take a number, Display PIN codes, Remote display, parking display

    Early on, I mentioned BCD (or digital), RS-485, Modbus and Ethernet

    They are not in the same category at all:
    The BCD I was thinking of was 8 bits, 2 digits, build your own. Not digit select, load digit, display digit; BCD to seven segment decoders also can display FuLL using 7-segments. There's another matrix that can actually do alphanumeric. There is also 5x7 and 5x9 matrices too (i.e. Dot matrix printer). With this method, it's likely no programmable control of brightness

    I introduced the RS-485 Adam module to get from digital to RS-485

    RS-485 is a multi-drop for 32 devices master/slave serial, wiring scheme; so a little bit of protocal is involved. Serial, is a one to one ASCII data. RS-485 is slow, but can do long distances because the signals are differential. Rs232 works when the devices are close. Everybody messes up RS-232. Levels used to be -3 to -25 V and 3 to 25 V and a whole bunch of signals to control a Bel 103 Modem.

    MODBUS takes RS-485 to another level. Lt has a protocal of sorts attached to it. There is also a full and half duplex version, I think. The talk about coils or relay coils. Those are digital I/O. I don;t know a lot about MODBUS and I only worked on two RS-485 things. So, I think everyone (MODBUS) knows what integers are, floats are, digital I/O is. Super simple explanation, Put the 8 bit integer 128 in memory location 3000 on device 32. At least that;s how I understand how it was in its infancy. PLC's (Programmable Logic Controllers) generally support it.

    We can say MODBUS runs on Ethernet and so does serial. Serial is packaged under Telnet, so I can go serial-telnet-serial if I wanted using a black box.

    Can you imagine an IP address for every parking space. Nope. So, lets have an IP address for every 32 parking spaces. RS485/Modbus will manage those 32 devices. That's your radio receiver that has to pick up the parking sensors. As you said, directionally beam formed fo the greatest coverage.

    RS485 can be both home run based or daisy chained. In daisy chain, there are terminator resistors at each end.
    The advantage of a hub is easier to troubleshoot. This isn't well known.

    The sensors are under the car, surface mounted and battery powered. The sensor supposedly has presence, probably low battery, and temperature minimum. It could have an ESN. It probably doen't have L3-10; or L3 space #10.

    Back to some other things, there is telnet and reverse telnet. Computer speaks telnet and a box at the other end might have 1-8 serial ports. they could be RS485 or RS232

    So, we can take these RS485 segments in our garage. Maybe a ceiling mount would do some of the floor above too.

    Ethernet tends to isolate somewhat the segments because of a transformer in each transceiver so long distance ground loops are non-existant.

    24 VDC is a very typical Process control power voltage, so the Wow people put all of the power as low voltage and aggregated it.

    A comment about Ethernet. POE switches are expensive, but high power is available. You can get up to 90W with current standards. http://www.linear.com/product/LT4275

    I have POE at home and it can get messy. I have one device, my DSL modem that runs off of POE. The UPS runs my server and network. Power glitches are not 100% recoverable without a reset unless the UPS is in place. The UPS takes care of server too. The UPS in theory can shut down the server gracefully.

    So, out of the blue, I knew about this: https://www.digi.com/products/serial-servers/serial-device-servers/portservertsmei#specifications

    https://www.digi.com/products/serial-servers/serial-device-servers/portservertsmei#specifications

    One of the 5 digit displays said it doesn't support low voltage power only 120 V. Power is a real pain.

    That one early company *take-a-ticket* didn't really have a way to utilize their display for another purpose.
    It did offer WIFI control of a specific function. PIN numbers. I don't even know what that is. Control is by the web and therefore I THINK it's possible to control problematically via something like curl or get/put. Missing is a decent IP rating and brightness control.

    For a DIY thing, the Wow company did the meat in a PLC or even SBC (Single Board Computer) When you start logging or doing accounting, thats the job for the PC.

    Here's https://spothero.com/philadelphia/downtown-parking a neat parking app. A display of free and handicapped spots in the front of the garage could be useful. e.g.

    SPOTS
    **********100
    HP*********6 (Use the handicapped symbol)
    EV Ports***10

    Providing Zoning OK with it.
     

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