Power Bus

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Short Definition

The bus that connects the outputs of a booster to the track or accessory decoders.

Typically a pair of heavy gauge wires connected to the booster output, either directly or via a power management device. Heavy gauge wire, such as AWG 10 to AWG 14, can handle the higher current demands required by Digital Command Control operations. It may also be called the track bus. Unlike analog power supplies, a Digital Command Control Booster can supply a much greater amount of current (amperage) to the track.

Instead of the all the current being carried by the rails to every point on the layout, the bus will distribute the current in addition to the rails.

The power bus will run parallel to the track, and at intervals a drop will be made from the track to the power bus. This has the effect of placing a low resistance wire in parallel with the higher resistance rail, which reduces voltage drop. For Digital Command Control, an acceptable loss is 5% of track voltage, to a maximum of 10% at 5A.

Although it may sound like an unnecessary expense and additional work, the bus will prevent problems and possible damage to components, while increasing reliability. If there is too much resistance in the circuit, power protection systems may not function as intended.

For bus termination (also called a snubber), see the article on Bus Termination.

See related articles on track wiring for more information and guidelines.