Summary: The booster combines power from the power supply with commands from the command station and delivers the resulting digital signal to the track and layout accessories.
Some Digital Command Control systems combine both the command station and booster into one package. For this definition, the booster is a separate device which requires instructions from an external command station.
What Does a Booster Do?
It requires two inputs to function: a data stream from the command station, and power from the power supply. The output is a digital waveform that is supplied to the track. It really functions as an amplifier, taking a digital level signals from the command station and amplifying them to track level voltages.
Think of a component audio system.
You have in input device, such as a tuner or CD player. By itself, it cannot provide enough power to drive a speaker. The input device is connected to an amplifier, which boosts the low level signal to a level sufficient to drive a speaker. The booster functions as the amplifier, taking the logic level (low voltage and current) signal from the command station and amplifying it to drive the track.
The booster is sometimes referred to as a the "Power Station". Since the booster contains no intelligence (non-thinking), it can be thought of as the "Pack Mule" of a DCC system as it is responsible for combining the intelligence from the command station with the power from the power supply. Some boosters may not have autoreversing, where others do.
Booster Power Regulation and Protection
Boosters are responsible for the following tasks:
- Convert the incoming AC or DC power into a local internal DC power source suitable to drive the track.
- Provide short circuit protection, so any short circuits will trigger the circuit breaker to cut power to the track before something is damaged.
- Optionally provide a regulated voltage for the track.
- Provide an automatic resetting "Circuit Breaker" function.
- Convert the command station's digital level signals into a DCC track waveforms with suitable voltage and current to run locomotives.
You might think it's best to have a single, large, booster/command station to power your entire layout. However, you will soon learn, it's typically best to have a couple of smaller boosters distributed around your layout. The reasons include: Additional trains, reverse sections, and to isolate derailments.
Boosters are available with opto-isolated inputs, if that feature is required. The picture below shows one booster with a sticker stating "opto" on it.
To add additional boosters, you must electrically divide your layout into two booster districts, connecting the original booster to one district and the new booster to the second district. The booster may need a separate power supply, and must be connected to your DCC system's throttle bus. By connecting the booster to the throttle bus, all boosters on the layout will send out the same commands to all sections of the track. This allows trains to receive commands, even if they are crossing between booster districts. Never connect two boosters to a common section of track, as this can destroy them if one goes out of phase.
Whereas a power district is one of several districts fed through a power management device by a single booster, a single district fed exclusively by one booster is called a booster district.
- Boosters should all have the same ampere (current) output. Combining a high current booster with a low current one, such as an 8A and a 5A booster, could result in destruction if an event connects the booster's outputs together. If possible, use a power management or circuit breaking device between each booster and the track.
Suggestion: Double gap the tracks to fully isolate the boosters. That is, both rails need to be cut at the same spot. Otherwise you can create a short if one booster district goes out of sync with the others.
- If the train stops at a gap, the boosters may be out of phase. Disable auto-reversing if equipped, as this can cause both boosters to enter an endless loop trying to match the other's constantly changing phase. Reversing the track power connections on one booster can correct that issue. You may need to make provisions to easily reverse the connections on a booster if it occasionally goes online out of phase with the other boosters.
- To prevent boosters from going out of phase during power up, ensure the throttle network carrying command station signals to the boosters is active first by powering up the command station, then the boosters. Otherwise boosters can go online out of phase with other boosters and the command station's DCC signal.
Warning: Do not wire boosters in parallel. This will lead to melted plastic and fried boosters. You cannot simply wire them in parallel. You must connect separate sections of track (power districts) to separate boosters.
Caution: Read and follow the manufacturer's directions for the booster and your DCC system on how to properly wire an additional booster.
Common Ground: Be sure to wire a common ground between boosters. This way they all have the same reference point for ground. Power management devices may also require grounding to the command station or booster. This can also function as a return when current needs to return to the source.
- This ground is not the same as the ground provided by your house wiring. You should never tie the low voltage side of your DCC system to house ground.
A booster is rated for amount of current it is capable of delivering to the track. If you demand more current than it can supply, it will simply shutdown.
If you notice the trains are starting to slow down when multiple trains are running, that's a sign you are reaching the limit of your booster - it's time to add additional boosters.
Typical boosters deliver 4 to 5 amps, and can be as high as 10 amps. This may be enough to run a train or two in the garden, or almost a dozen HO or Z scale trains.
Sooner or later, a train will derail causing the booster to go into protection mode.
Once this happens, all trains using that booster will come to an immediate stop. If you want to prevent a derailment, say in a switching or staging yard, from stopping all the trains on a layout, power these sections with a separate booster. This way, if someone accidentally shorts the tracks while putting locos on the tracks, the rest of the layout will continue to operate.
There are alternatives for adding boosters to get the above listed features, except for adding a booster for additional power.
These modules typically go between the booster and the section of trackage (power district).
For example, a reversing power module would connect between the booster and a reversing section, but the rest of the track is still powered directly from the same booster. The moment a wheel connects between rails of different phase, the reverser springs into action and makes them both the same phase. A typical application would be a reverse loop.
A booster can also be used to create a dedicated bus for stationary decoders, isolating the stationary decoders from events occurring on the track. This is a useful method if the stationary decoders employed lack the ability to connect to a throttle network such as LocoNet or XPressNet.
See the instruction manual for instructions on connecting the booster, and any additional boosters. It will also illustrate how to connect the input signals to the booster.