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Thread: SNVT Conversion

  1. #1
    Join Date
    Jun 2005
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    SNVT Conversion

    I have an issue with an Altivar 61 vfd with Lon card. I need to bind enable, speed and status to a Trane MP580. The problem is that for one the status off the drive is nvoStatusWord SNVT_State and the MP580 does not have an NVI of that type . The other issue is the enable. This is a SNVT_switch but it needs a state of 0 or 1 for enable and a value of 0-100 for the speed setpoint. Again the MP580 does not allow to write that to an NVO. Any ideas or suggestions would be great.

  2. #2
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    Mar 2003
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    Dave, I have never worked with an MP580 but I just took a look at the xif file. It looks like there are 30 nvoSwitches in that device. I would be surprised if you cannot write a value to any of them. Are they all bound to the BOs of the device?

    As far as the 'status' of the drive goes I don't see why you would have to bind that SNVT to the MP580. Device status usually contains a lot of information, therefor the 'word' SNVT. All you probably need is something like run state and alarm.

    If this information has to be available to a 'front end' then the network LON connection should be fine but you might be better off hard wiring these points from the drive to the inputs/outputs of the MP580 depending on the distance to the drive.

  3. #3
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    Feb 2005
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    Where it's dark & damp
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    I think your hosed on the state snvt but you can write and use snvt switches with the 580. Plop some switch NVOs on your wire sheet and write to them in your progam. Then bind them with Rover or whatever tool you are using to the SNVTs contained in the drive. You can see some stat snvts with the BCU and then pass it back to the 580.

  4. #4
    Join Date
    May 2002
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    Why do you want to bind SNVT_state from the drive to the controller? It is simply an informational point.

    I think (reading between the lines) you should read this article from Loytec.

  5. #5
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    Jun 2005
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    The reason for binding the SNVT_state is to show drive status to the logic in the MP580. The NVO from the drive is a status word type. The MP580 does not have such and NVI to bind it to. The contract calls for no hardwire at all to the drives. Everything is to come and go via lon bus. I needed some way of getting status. Despite not wanting to I had to take and NVO off the drive telling me the current hertz the drive is running at and then use a simple logic of if greater than 2 I have status. No BCU to use either job is an integration to Tridium and we do not have the front end. Anyway thanks for the input but I got it. Needed to link both a binary switch NVO and analog switch NVO off the MP580 to the NVI for enable/speed

  6. #6
    Jslimjeff knows MP580's like the palm of his hand.

  7. #7
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    May 2002
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    Anybody have the Altivar NVO list?

  8. #8
    Join Date
    Mar 2008
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    Tennessee
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    Sysint,

    No I don't right now but I can get it if I know which drive, but I believe Dave has access to the same info I do.

    Dave,

    Typically with any drive you can define any output I'm not saying this is the right answer but you could configure one binary on the drive to be on when it is running and off when it is not then bind NVI_SWITCH_01 in the 581 to that NVO for output status. just an idea, you come up with some tough ones.

  9. #9
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    May 2002
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    I'm surprised they don't have output for frequency, etc... which would give more opportunity to get SNVT_switch information in individual variables. From the web site it appears that the organization of information and documentation for Altivar is poorly done in regards to communication options. Dave said it was an Altivar 61 series. If they have more than one LON card for this series, then I suggest running to ABB for a drive...

  10. #10
    Join Date
    Jun 2005
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    285
    The drive does have a running frequency output and that is what I am using to determine status. They are working fine now not quite the way that drive manufacturer intended but it is working.

  11. #11

    Basic Lon Rules

    You are not able to bind to a nvo and write value to that NV. An nvo is per definition read only, produced by the device and kan via a binding (implicit or explicit) be propagated to a nvi.
    If you need to send one SNVT type to another SNVT type, you need something in between. An L-Proxy is a simple option, or a freely programmable Lon device (e.g. TAC Xenta). Normally you need some logic in the casting/conversion operation trnaslatin one SNVT type to another.

  12. #12
    Join Date
    May 2002
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    Both those are really expensive options when he needed to do what he did.... look at the other variables and worked with what his controller could handle.

  13. #13
    Join Date
    Aug 2007
    Posts
    21
    Hi Dave,
    Rover and bindings is bad news, can you not set the vsd up as a gld in summit,make and refrence points in summit then transfer to and from MP581 as Variables this is assuming you have a bcu and this isnt a standalone site? i have also bound to a/o status and b/o status snvt's on the MP581 before this will use inputs/outputs on the controller(in your program actually control physical points then bind to the status snvt's for those points) and just make sure you have good documentation otherwise some clown will go to site and think they are spare points?

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