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  1. #14
    Join Date
    May 2002
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    9,564
    Quote Originally Posted by Dowadudda View Post
    ...It all boils down to device adress, board and point right?...
    Not always. For instance, in LON you have a Neuron ID which is the device unique identifier, and it also gets a physical location address to it dependent on where it's installed. Many bacnet devices are assigned software or dipswitches and communication baud rates.

    Anyway, even some of your supermarket systems speak LON or other protocols so you are working with things already. Here's the thing about that-- many OEMs utilize protocols, but few train people about them. They are strictly interested in their narrow application, even they at times don't realize how to do things. It shows in their product anytime you want to use it with other products.

    If you are interested, start reading. They are many ways to get information. For instance, at the Loytec site I'd read their application notes. I'd buy the LON book(s) and understand what the ideal standards are and then you can realize what you are getting.

  2. #15
    Join Date
    Nov 2006
    Location
    Mirabel, QC, Canada
    Posts
    88
    Hello Dowadduda,

    I want a pizza (I am a controller, or simply a device initiating something)
    I pick up the phone (the phone is Lonworks, modbus, bacnet - no more!)
    I call a pizzeria. (another device)

    Hey, wait a minute. How did I know which number to call? Either I was told by my wife (the configurer of the site) or I looked up the yellow pages (an automated discovery service).

    The number to call is the other device address. In either cases, I have to remember that number if I want pizzas in the future, because my wife is gone on another site, and looking up the yellow pages is a slow process. I will keep a post-it on the fridge (non-volatile memory in the controller device)

    Now I issue my specific order by talking english to someone that understand english (english is either a collection of 'standard network variable types - SNVTs, or how to write to a specific modbus register)

    I order one medium pepperoni and cheese. (I have just written into a particular network variable input (nviOrder of type SNVT_PizzaOrder on the other device), or written into a modbus register in the other device). In either cases, I have written a specific value (medium pepperoni and cheese).

    Cool isn't it. It's just speech over a phone line. In reality, it is bits serialized over a digital network. And it is just a virtual command so far. Nothing tangible. The real pizza ain't at my door yet.

    The pizzeria makes the pizza I ordered (the other board clicks the desired relay). But wait. How did it know which relay to click? The boss at the pizzeria (another installer, unless it was my wife again) told the employees at the pizzeria (the device software) how to make a pepperoni pizza by configuring or assigning a pepperoni pizza with the proper relay.

    I will skip the rest of the story, and not explain how the pizza gets over here, partly because it is no longer relevant, and because the pizza just came in.

    If you want to understand a protocol, a generic description is made by the OSI 7-level model. All the way from the physical level 1(the wires) to the application level 7 (the other device). It is really boring, because there is nothing specific like a pepperoni pizza in it.

    Hope this helps speed up your reading.
    -------------------------
    CO2 Racks Rock !

  3. #16
    Join Date
    Nov 2006
    Location
    Mirabel, QC, Canada
    Posts
    88
    Oops, posted twice for some reason...
    Removed identical message
    Last edited by yroy; 10-27-2008 at 11:17 AM. Reason: posted twice same message
    -------------------------
    CO2 Racks Rock !

  4. #17
    Join Date
    May 2002
    Posts
    9,564
    Dowa, Here's something for you to listen to... once you get past the introductions it picks up..
    Networking Troubleshooting Al Mouton

    Al had a comfortable way of explaining things.

  5. #18
    Join Date
    Apr 2007
    Location
    San Diego, CA
    Posts
    1,338

    thanks, now I'm hungry

    Yroy, nicely done!

    here's a wikipedia link to the 7-layer burrito:
    http://en.wikipedia.org/wiki/OSI_model
    just remember:
    Please Do Not Throw Sausage Pizza Away
    or
    Please Do Not Tell Sales People Anything
    Physical, Data Link, Network, Transport, Session, Presentation, and Application

  6. #19
    Join Date
    Jun 2001
    Location
    Michigan
    Posts
    12,077
    how often do you guys run into a situation where one can not get the two different devices integrated?


    BTW. Great feedback from everyone. I am getting increasingly into this work and before long I can see mysef totally transitioning down the road.

    Thanks guys. Really appreciate it. I intend to read all the info and then come back with more quetions.

    I think that I now see that, I am thinking the guts of the systems is board and point. And thats the minor part. The major part is, having three different languages all talking about the same board and point.

  7. #20
    Join Date
    May 2002
    Posts
    9,564
    When people don't follow standards things always get aggravating. Just look at the DataAire thread where the guy absolutely couldn't get it working.

    Not all manufacturers are created equal. Actually, most would be better suited to go with a third party that knows what they are doing (for the most part) and have dedicated resources to communication other than an after-thought. However, even with those they have strengths and weaknesses. For instance, ALC and Carrier LON interfaces are garbage for the most part. By contrast, I've haven't had many issues with Trane LON interfaces for communication. I'd say it isn't the fault of the protocol, most often it's the company working with that protocol or how they make their interfacing boards. Or, in the case of some, how they try NOT to work with it.

  8. #21
    Join Date
    Nov 2006
    Location
    Mirabel, QC, Canada
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    88
    Quote Originally Posted by Dowadudda View Post
    how often do you guys run into a situation where one can not get the two different devices integrated?
    My experience is with Lonworks. There are many different SNVTs to convey temperature (unfortunately). For example, there is SNVT-temp-float and SNVT-temp-p. If device A uses a different type then device B, the temperature cannot be exchanged between the two devices.

    Echelon, a long long time ago, figured that poor little 3120 chips would not have a floating point library, whereas the 3150 would, most likely. Hence the multiple types.

    The good news is that LonMark has specified that in HVAC, one should always use SNVT_temp_p. So an HVAC device to an HVAC device is not a problem. However, an HVAC device to a non-HVAC device might be a problem.

    If the SNVT cannot be changed dynamically from one type to another in device A and device B, then you need an intervening device C that just acts as a SNVT converter.
    -------------------------
    CO2 Racks Rock !

  9. #22
    Join Date
    Nov 2006
    Location
    Mirabel, QC, Canada
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    88
    Quote Originally Posted by sysint View Post
    For instance, ALC and Carrier LON interfaces are garbage for the most part.
    Except of course for Micro Thermo Technologies which is owned by Carrier Electronics. We design Lonworks controllers (not gateways) since 1995.
    -------------------------
    CO2 Racks Rock !

  10. #23
    Join Date
    Jan 2005
    Location
    USA
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    Quote Originally Posted by Dowadudda View Post
    how often do you guys run into a situation where one can not get the two different devices integrated?
    .
    The only problem like that happens when one mfr has differant points than another. For instance Trane Rtu lonboards have a point for daytime warmup and honeywell vav controllers do not, so the Rtu would ramp up 100% and the boxes are clueless to what is happening and the Rtu will trip off on high static. These type of problems can take a long time to figure out but they only fool you once if you are careful or not forgetful.
    "It's always controls"

  11. #24
    Join Date
    Apr 2007
    Location
    San Diego, CA
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    Quote Originally Posted by skwsproul View Post
    The only problem like that happens when one mfr has differant points than another. For instance Trane Rtu lonboards have a point for daytime warmup and honeywell vav controllers do not, so the Rtu would ramp up 100% and the boxes are clueless to what is happening and the Rtu will trip off on high static. These type of problems can take a long time to figure out but they only fool you once if you are careful or not forgetful.
    You should bind your AHU's Discharge Air Temp to nviDuctInTemp (snvt_temp_p) on your HW VAV controllers. This wil give the VAVs a clue as to what's happening.
    Also, you've got nviAppplicMode to play with, which is a standard snvt type 108.
    I'm not sure why a daytime warmup would ramp up your unit to 100%...

  12. #25
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    Jan 2005
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    USA
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    Quote Originally Posted by digo View Post
    You should bind your AHU's Discharge Air Temp to nviDuctInTemp (snvt_temp_p) on your HW VAV controllers. This wil give the VAVs a clue as to what's happening.
    Also, you've got nviAppplicMode to play with, which is a standard snvt type 108.
    I'm not sure why a daytime warmup would ramp up your unit to 100%...
    Yeah did that. The daytime warm up works like morning warmup. The vfd goes to 100% opening all boxes to warm the building quickly for a period of time than they go back to normal. I have no idea why you would do that in the middle of your occupied time.
    "It's always controls"

  13. #26
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    Apr 2007
    Location
    Amarillo by mornin'
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    853
    Quote Originally Posted by sysint View Post
    For instance, ALC and Carrier LON interfaces are garbage for the most part.
    What kind of interface are you referring to? What we use for an interface is a SLTA-10 to a LGR (router).
    "It's not that I'm smart, it's that I stay with the problem longer”
    Albert Einstein

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