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LNS Programmer's Guide

LNS Network Installation Scenarios

To understand what is required to install LONWORKS devices on a LONWORKS network,

you should consider the types of control systems that L

ONWORKS networks replace.

Many conventional control systems use wiring harnesses or point-to-point wires. In these

systems, the wiring between devices serves two purposes when the devices are installed.

It physically interconnects the devices, and it determines which control signals should be

sent to which device. Once attached to the wire, the behavior and interaction among the

devices is completely defined.

Other control systems use a master-slave architecture, and require DIP switches or dials

on each device to specify the device’s address. The device addresses are predefined and

based on the control algorithm in the master. When these devices are installed, the

master polls each address, and the appropriate device responds. Such systems are

usually limited to a small number of devices, and changes to system behavior usually

require resetting the DIP switches on each device, and modifying the master control

software.

A L

ONWORKS network consists of intelligent devices called nodes or application devices

that are connected by one or more communications media. Application devices

communicate with one another using the L

ONWORKS protocol (also referred to as the

LonTalk protocol). Each intelligent device on the network, e.g. a programmable

thermostat in a building control system, is a L

ONWORKS application device. The devices

communicate with one another across a shared communications medium, such as a

twisted pair cable, a power line circuit, or an RF link. Figure 5.1 shows the wiring

difference between a conventional system and a L

ONWORKS network.

Figure 5.1 Wire Reduction in a L

ONWORKS Network

The devices on a L

ONWORKS network contain objects that respond to a variety of inputs,

and produce desired outputs. Although the function of a given device may be quite

simple, the interaction among devices allows L

ONWORKS networks to perform complex

tasks. A benefit of L

ONWORKS networks is that a small number of common device types

can perform a broad spectrum of different functions, depending on how they are

configured and logically connected.

In a L

ONWORKS network, devices share their physical media (e.g. twisted-pair wire or a

power line circuit), which eliminates the redundant point-to-point wiring found in

conventional control systems. Without point-to-point wiring (e.g. a light switch wired to a

lamp) the physical attachment no longer uniquely identifies a device. In a L

ONWORKS

network, the physical attachment only provides a path for devices to send and receive

messages. It does not tell the devices which other devices they should send data to.

Therefore, in addition to physically attaching the devices to the network, you also need to

perform the following tasks when installing a L

ONWORKS network:

• Assign a network address to each device. A network address identifies

which application device a L

ONWORKS messages should be sent to, just as

a postal address identifies which house a letter should be delivered to. A

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