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67Re: Meeting in Norfolk, Virginia

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  • Steve Karg
    Oct 13, 2004
    • 0 Attachment
      BACnet - Lighting Applications Working Group
      Meeting Minutes
      5 October 2004
      Norfolk, Virginia

      Participants - Affiliation
      --------------------------
      Steve Karg - Lithonia Lighting
      Robert Hick - Leviton Lighting
      David Fisher - Polarsoft
      Pete Baselici - The Wattstopper
      Steve Bushby - NIST

      The meeting was called to order at 8:40am after introductions and
      greetings from our hosts.

      We reviewed the minutes of the last meeting. David Fisher pointed out
      correction: DMF011-13 should be DMF011-3. The minutes were approved
      as amended.

      The meeting agenda was reviewed and approved.

      Liason Reports
      Pete Baselici reported on NEMA activity. DALI protocol development is
      proceeding. Work is being done on selecting parameter banks. The new
      joint committee DALI protocol allows multiple controllers. NEMA
      working with IES protocol committee.
      Steve Bushby reported on a NIST-IAR (inter agency report) on lighting
      applications written by Steve Treado that is due to be published soon.

      LA-WG submitted proposal discussion
      Steve Karg proposed that this committee drop DMF-018-3 in favor of
      DMF-011-6 and DMF-019-3. Reported consensus at Nashville was that
      DMF-018-3 and DMF-019-3 were redundant if DMF-011-6 was adopted and
      therefore not necessary. Group discussion ensued and consensus
      emerged that 019 contains simple changes to BO BV that may provide
      easy way for mfg to provide on/off lighting control. Group discussed
      about when to implement BO / BV instead of LO object. Steve Bushby
      moved to abandon DMF-018-3 and retain DMF-019-3 and DMF-011-6 (vote 5
      for and 0 against). David Fisher agreed to add language to DMF-019-03
      to clarify the use case for BV in addition to BO.

      Multiplexer Object proposal STK-004 and Tripped Breaker Status
      proposal STK-015 are in the queue for SSPC-135 review.

      Scheduling Famous Times
      David Fisher presented DMF-028-1 for Famous Times. He explained of
      use of "Offsets" as time value relative to Famous time. This proposal
      may additionally require the rewriting of several clauses in the
      schedule object. David Fisher suggested an alternate method of
      encoding of BACnetTimeValue which would utilize the illegal values.
      The group discussed how to handle a reference time versus an
      enumerated famous time and their possible encoding format.

      Hours | Minutes | Seconds | Hundredths
      --------------------------------------------
      Legal | | |
      Values 0-59 | 0-59 | 0-59 | 0-99
      --------------------------------------------
      Famous | Famous |
      Time 0xFE | time |16 bit signed offset
      | enum. |
      --------------------------------------------
      Referenced |Reference|
      Time 0xFD |array |16 bit signed offset
      |index |
      --------------------------------------------

      The group discussed the use of the 16 bit signed integer offset, and
      decided that it should have a limited value of +/- 720 minutes, rather
      than an unlimited value of a signed 16 bit integer (+/- 32768).

      The famous times enumeration was discussed, and it seems that
      initially only Sunrise and Sunset may be necessary. The group decided
      that the enumeration should include 0-127 as reserved BACnet Famous
      Times (ASHRAE reserved values) and 128-255 to allow additions.
      Consensus of the group was to go ahead and create proposal without
      adding the 135.1 testing requirements to the proposal in order to
      float the idea to the committee.
      David Fisher will produce DMF-028-2 based on these ideas.

      Speed of Lighting Control on the Wire.
      Steve Karg described problems he had with sluggishness of BACnet
      lighting control. One of his solutions was to use asynchronous
      WriteProperty services instead of synchronous. Robert Hick described
      need for 125ms response time within field of view (i.e. Ballroom).
      Steve Karg reviewed several protocols used in lighting control:
      1) DMX 512 which sends a variable length frame which contains the
      lighting level for up to 512 devices at 250kbps giving up to 49
      updates per second to all devices on the wire. The protocol is a
      single master protocol. It is the industry standard for theatrical
      lighting.
      2) Proprietary protocol 1 sends a variable length frame containing a
      fade time and up to 128 lighting levels (frames can be chained for up
      to 2048 lighting levels). The protocol operates at 38.4Kbps and gives
      about 300 updates in 100ms. The protocol is a multi-master token
      passing protocol.
      3) Proprietary protocol 2 sends a variable length frame containing a
      lighting level and a fade time that affects up to 16 devices and
      operates at 57.6kbps. The protocol operates as a single master with
      slave reply.
      4) The DALI protocol runs at 1200 bps, and can have up to 64 nodes on
      the wire. The protocol is designed for multiple masters, and the
      lighting devices act as slaves which can reply. The lighting devices
      can also be members of groups and can also store scene level
      information.

      Problems with MS/TP and 156kbps ARCNET speed seem to stem from the
      size of the packet, the waiting for acknowledgements, and sending
      individual packets to each device. What might possibly work is some
      sort of unconfirmed broadcast write service. Another suggestion is
      using a "group number," which may not address setting light to
      different levels. There was a side discussion of how some
      manufacturers store presets levels at the control device versus
      storing the preset levels at the dimmer/relay device. The group
      discussed the need of other BACnet control sectors that may need a
      fast unconfirmed broadcast write. It was suggested that we start by
      defining way of accessing presets or scenes.

      David Fisher agreed to write a proposal for a broadcast group write of
      mode.

      Modeling enable/disable ON/OFF using out-of-service
      Steve Karg discussed need for way to model the disabling control
      stations or individual buttons. David Fisher suggested that BACnet
      "overridden" would be more appropriate than out-of-service.

      The next meeting is planned for Orlando, Florida sometime around
      February 5-9.

      Submitted by Robert Hick with edits by David Fisher and Steve Karg.
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