Standalone LocoNet®

This page is a work in progress

A "Standalone" LocoNet is a LocoNet bus which does not have a command station.

There are several situations where a standalone LocoNet bus is useful. Some of these situations are listed here:

When using LocoNet peripherals with a non-LocoNet DCC command station.
When using LocoNet peripherals with a non-DCC railroad.
To isolate LocoNet peripherals from LocoNet throttle activity.

This page gives some general suggestions for implementing a standalone LocoNet as well as suggestions for configuring JMRI software to make use of the standalone LocoNet.

General ideas
JMRI Configuration
Hardware Considerations
Examples
References

General ideas

JMRI Configuration

Hardware Considerations

A "LocoNet" bus implementation which has all signalling required by all LocoNet devices requires a LocoNet-based command station, such as the Digitrax DCS100 or Digitrax DB150. Some applications do not need all of the functionality provided by the Digitrax command station. This is where the standalone LocoNet bus is useful.

Different LocoNet devices require different features of Loconet". Key LocoNet features which are normally provided by a LocoNet-based command station include: "Slot management", "RailSync" signal, LocoNet data signal termination, and fast clock master. The table below shows some LocoNet devices and their requirements.

Command Stations and Boosters
Device	Slot Management	RailSync	LocoNet data signal termination	Fast Clock Master
Digitrax DCS100 (as command station)	Provides	Provides	Provides	Provides
Digitrax DCS100 (as booster)		Required
Digitrax DB150 (as command station)	Provides	Provides	Provides	Provides
Digitrax DB150 (as booster)		Required
Non-LocoNet command station		Can provide *
Commputer Interface Devices
Device	Slot Management	RailSync	LocoNet data signal termination	Fast Clock Master
Digitrax PR3 (in MS100 mode)	Optional		Required, can provide
LocoBuffer, RR-CirKits LocoBuffer-II/LocoBuffer-USB	Optional		Required, can provide
LocoNet Throttles
Device	Slot Management	RailSync	LocoNet data signal termination	Fast Clock Master
Digitrax DT100x/DT200x/DT300x/DT400x/DT402x throttle	Required	Optional (only for power)	Required	Optional
Other LocoNet Devices
Device	Slot Management	RailSync	LocoNet data signal termination	Fast Clock Master
Digitrax LNRP		Required	Required
Digitrax DS54/DS64			Optional
Digitrax BDL16/BDL162/BDL168		Required	Required, can provide
Digitrax PM42		Required	Required
Digitrax SE8C			Required
UR90/UR91/UR92	Required		Required
(DIY)LocoIO/LocoServo			Required
Team Digital SIC24/SIC24AD/SRC8/SRC16			Required
RR-Cirkits TC-64			Required
Logic Rail Technologies LocoNet Fast Clock			Required	Required, can provide
* Some circuitry may be required to generate the RailSync signals from a non-LocoNet booster.

LocoNet Data Signal "Termination"

Hardware which can provide LocoNet Data Signal Termination

BDL16, BDL162, BDL168
PR3
LocoBuffer, LocoBuffer-II, LocoBuffer-USB

Do-it-yourself LocoNet Data Signal Termination

LocoNet RailSync Signal "Generation"

RailSync from a Digitrax command station

RailSync from a non-Digitrax command station

RailSync as a power source

"Sneak paths" and Computer Interfaces

When multiple devices share different types of electrical connections, unexpected current paths can be present that can cause malfunction or component failure. A properly designed and implemented system prevents these problems.

A good example of this type of problem is the connectivity that begins at the (power receptacle) wall outlet, through power supplies, boards, interface devices and computers. If there is "electrical connectivity" between the wall outlet and the output of a power supply, and the power supply is electrically connected to a board such as a BDL16x, and the board is electrically connected to a LocoNet bus, and the LocoNet bus is electrically connected to a computer interface, and the computer interface is connected to a personal computer, and the personal computer is connected to a power supply, and the power supply is connected to the wall outlet, there could be a "sneak path" for electrical current around the electrical connectivity loop. If the electrical current happens to exceed the ratings of any component in the loop, there can be a failure of that component, and perhaps components to which it is connected.

How can such a problem be avoided? By careful planning of the electrical connectivity within a system, and inclusion of some form of "isolation" where electrical connectivity concerns arise. It is usually very difficult to determine the electrical connectivity within a computer power supply, so it is generally a good idea to isolate the computer from the remainder of the system.

Isolation of LocoNet from the computer is recommended. The LocoBuffer-II and LocoBuffer-USB computer interface devices provide "optical isolation" of the LocoNet signals from the computer electrical signals if the LocoBuffer-II/-USB is not configured to provide LocoNet termination.

Other computer interfaces can be isloated using 3rd-party isolation devices. Placing a USB hub with optical isolation between the computer and the USB device, or an RS232 optical isolation device between the computer and the RS232-based interface device might provide a safe and functional solution. Note, though, that some users have reported issues when using a USB hub (whether optically isolated or not) with the PR3.

Similar "sneak path" problems can happen when sharing a single power supply for multiple device types that share other connectivity. A LocoNet cable can provide that "other connectivity", so devices which connect to LocoNet must be powered with care. A safe "general rule" is that a power supply should be connected to, at most, one type of board.

Examples

References

LocoNet® is a registered trademark of Digitrax, Inc.