Summary: A Programming Track aids in programming multifunction decoders. They can be an independent segment, or a spur on your layout.
See the Video.
A programming track is used to safely program Multifunction Decoders using Service Mode. It is easier to have a portion of your layout track to double as a programming track. This minimizes handling of finely detailed locos on your layout and allows you to simply drive your loco to the programming section, and read/change values of the decoder. It is best to have your programming track near the programming device (Command Station, SPROG, or Computer). Every layout should have a program track. It does not have to be on the layout, it could be a test track at the workbench.
- 1 Reasons for the Program Track
- 2 Independent Program Track
- 3 Program Track on the Layout
- 4 Programming Track Boosters
- 5 Notes
- 6 Video: Wiring a Program Track
- 7 Video: Build a Portable Program Track
- 8 Further Reading
Reasons for the Program Track
The best reason for a Program Track is to prevent damage to a multifunction decoder.
- The programming output on the booster is current limited. Boosters which lack a program output usually include a resistor that is temporarily installed in series with the track circuit to limit the current. The resistor is not needed for normal operations. The NMRA Standard S-9.2.3 defines the Service Mode/Program Track. It requires a separate, isolated track for programming which is both monitored and current limited. The multifunction decoder will acknowledge an instruction with an increased current draw of at least 60mA for 6ms, often by pulsing the motor.
- Some multifunction decoders have built-in short circuit protection, others do not. An incorrectly wired multifunction decoder can be destroyed when exposed to the track voltages used on a DCC layout.
- Any new, untried multifunction decoder install should never be placed on the layout, but first on the programming track. Should there be an error, the multifunction decoder will not be destroyed on the program track, due to the current limiting feature.
- For multifunction decoders with sound, an optional programming track booster can also be installed to feed the programming track. Not all systems require this, but many sound decoders cannot be programmed without one. See below for more on programming track boosters.
- It is too easy to accidentally program all the multifunction decoders on the layout with Service Mode programming.
The disadvantages of having a programming track:
- The dedicated programming output is usually only found on more sophisticated (read expensive) boosters.
- A dedicated programming track must be constructed, either on your layout or the workbench.
- The locomotive/decoder combination to be configured must be moved or placed on the programming track.
- Motor operation and functions cannot be used or verified on a programming track. That must be done on the layout or a DCC powered test track
Of course, there are advantages to having a program track.
- Progamming is done in a controlled manner, with low voltages and currents, eliminating the risk of damage possible when a miswired multifunction decoder be exposed to full DCC power on the mainline.
- The Program outputs are only active during programming.
- Multifunction decoder address is not required to configure it. Also eliminates the possibility of programming all the motive power on the layout.
- CV values can be read and recorded manually or via software for easy record keeping
- A mistake made in the multifunction decoder's wiring will be forgiven. It will not cost you an expensive decoder.
Refer to NMRA S-9.2.3 for more information.
Service Mode Programming
The program track operates in what is known as Service Mode. Most boosters have a dedicated program track output, which switches on when in use. Operations Mode uses the main track output. On boosters which lack a program track output, the main track is used for both modes. The danger is that when the booster switches to programming mode, Service Mode will write changes to all the decoders on the layout!
The PROGRAM output on a booster must never be connected to the TRACK output!
Independent Program Track
An easy solution to create a program track is to use an independent segment of track. This can be on the workbench or near the layout. The programming outputs of a command station are connected to the track for configuring a multifunction decoder. A toggle switch can be used (Break before Make type) to switch between Program and normal operation.
Using a second DCC command station dedicated to the program track makes programming convenient and easy. NCE Power Cab users could purchase additional components for the Power Cab to utilise it for the programming track, such as the Auto Switch. A SPROG or a Digitrax Zephyr is another option. Adding an interface for the computer will make a complete programming setup.
Program Track on the Layout
The biggest problem with a programming track on the layout is that if the a train enters the programming track, and the switch is set for programming, the power pickups of the locomotive will short the two segments together. To prevent this, you must isolate the programming track from the running track so that should a locomotive enter or exit the programming track when it is set for programming no harm is done. This is accomplished with a segment of track between the program track and the rest of the layout which is dead during programming operations. This segment should be longer than your longest locomotive for safety.
With the solution provided below, the worst that will happen is that the train will stop once the last power pickup enters the isolation area. Some multifunction decoders may creep forward during programming as a method of acknowledging the command was accepted, which can be an issue when using a method like DecoderPro to write multiple CVs, particularly when programming a sound decoder.
The addition of a center-off DPDT (break before make) toggle switch allows the use of programming and normal modes on the track for testing.
Isolating the Programming Track
To prevent a locomotive from accidentally shorting the program track you need a section of track as shown below. The programming segment needs to be at least 50% longer than your longest locomotive and the isolating segment must be longer than your longest locomotive. The longer the programming track segment is the more useful it will be.
Remember, some locomotives creep forward during programming, so the longer the track the better. Modern decoders have an acknowledgement feature built in. A program such as DecoderPro will send a new CV value to the multifunction decoder. If it works, the decoder will acknowledge this by briefly energizing the motor. This sudden draw in current can be detected by the command station. DecoderPro can by the same method read the CV values. It just sends every possible value sequentially until the motor is energized. Thus, when programming or reading a large number of values the locomotive can creep forward quite a distance. Keep that in mind when planning the length of your programming track
Wiring the Programming Track
This is an example of how to connect a 4PDT (4 Pole, Double Throw) switch to the track. When the switch is in the normal position both sections of the track are connected to the layout and act as part of the layout. When the switch is the programming position, the program track (BROWN + BLACK wires) is connected to the programming device, while the isolating section (violet wires) is totally disconnected and the LED turns on. The red LED can be a signal near the track, or mounted between the track, or on the front of the facia, or both.
Why is a 4PDT Switch Used
Many modellers are of the opinion that two DPDT switches can be used. They are not incorrect.
Inevitably a mistake will occur or a switch will be changed accidentally, damaging the command station/booster. A 4PDT prevents accidental misconfiguration of the program track by only offering two possible states. Using two DPDT switches offers 4 possibilities making misconfiguration very easy to accomplish.
A Note Regarding Switches
The best choice of a 4PDT switch for your program track is a Center-Off version. This ensures that one circuit is completely disconnected prior to the new connection being established.
- Switches are available as "make before break" and "break before make". For this application, a "break before make" is essential, and a center-off version is the easiest way to make sure the switch breaks before making a connection. This avoids the possibility of momentary connecting the booster output to the programming track output terminals.
Wiring the 4PDT Switch
- Normal output to the track from the booster. In this mode, the program track and isolating section is connected directly to the booster output and function as normal trackage.
- Command Station
- Output from the Command Station or Booster's dedicated Programming Track outputs, if equipped. If your command station lacks these connections, consult the manual for the proper wiring of a program track, which may require a series resistor to limit the current in this mode.
The left half of the switch selects the power source that connects to the programming track (BROWN + BLACK wires). When the switch is in the Normal position, the programming track segment is connected to the layout, and acts as part of the layout. When the switch is in the Program position, the program track output from the command station is connected to the programming segment.
The right half of the switch controls the isolating track (RED wires). In the Normal position, the isolating segment is connected to the main line. In Program position, the isolating segment is totally disconnected from power, and power flows to the LED.
The LED can be a signal near the track, or mounted between the rails, or on the front of the facia, or both. Note: The LED is optional and may or may not work depending on the DCC system used. Some DCC systems will shutdown the main line when programming is active leaving the LED unpowered.
- Note Regarding the LED
- It would be advisable to connect another general purpose diode in series with the LED to protect the LED from being reverse biased when the track signal makes the Cathode more positive than the Anode. LEDs are not designed for high reverse voltages.
Check the switch operation with an ohmmeter to determine how the connections are made before wiring. They usually connect the terminals opposite the handle's position.
Programming Track Boosters
|Digitrax Zephyr||Yes||Not required if using Blast Mode|
|Digitrax DCS Series||Yes||May not be required with newer models, check manual|
|Digitrax DB Series||Yes|
|Lenz LZV100||Yes||Firmware greater than Version 3.6 should not require a booster|
|NCE Power Pro / Power House||Yes||See Power Pro section below|
|NCE Power Cab||No||NCE does not recommend their use.|
- This usually is an issue with Sound equipped Decoders. It will work on non-sound decoders as well.
If attempts to program the decoder result in unwanted changes, or a non-responsive decoder, a Programming Track Booster may be needed to overcome these issues. It would be connected between the command station/booster and the programming track, as per the manufacturer's instructions. Sound decoders arrived after the NMRA defined the DCC standard, so the basic requirements for programming a decoder, while adequate, often do not work with sound equipped decoders which require more current during programming. DCC Systems designed and manufactured in recent years, and recent decoder models, often do not require a program track booster for successful programming.
This device will often be recommended by the decoder manufacturer when there are difficulties programming the decoder. They are available from your dealer. If in doubt, ask your dealer, the decoder or your DCC System's manufacturer. They will advise if you need a program track booster or not.
A Programming Track Booster serves to make programming more reliable, and may also incorporate short circuit protection and basic diagnotics. It may also provide feedback to aid in troubleshooting a problematic decoder.
NOTE: This device will not solve problems created by the user during installation. Its sole purpose is to make programming more reliable. The device may not be needed, depending on the DCC brand/model chosen by the user. As always, consult the decoder and Program Track Booster manufacturer, or your dealer, to determine if this device would help.
Programming Track Boosters and NCE Power Cab
- DO NOT connect a programming track booster of any kind to an NCE Power cab. The programming track mode of the Power cab is a newer design that incorporates the ability to program sound equipped decoders.
The NCE Auto-SW detects the packets indicating program mode, and switches its output from track power to program track. It has one input from a booster, such NCE's Power Cab, and two outputs.
It works with booster which lack a dedicated output for the programming track. It is also suitable for use with the Digitrax Empire Builder, Big Boy or Challenger sets. When using Program on Main, it does not activate the program track. It eliminates the possibility of Ops Mode programming mode being activated and programming everything on the layout. Ops Mode commands are only sent to the program track.
If your booster does not have programming capability, such as the NCE Smart Booster, this device will not work with it.
NCE Power Pro Modification
The NCE Power Pro can be modified to increase the track current available during programming.
The outputs are protected from a current overload using small lamps to limit the current. Adding two additional lamps in parallel with the existing ones will double the current.
See Instructions here for more details on this and other modifications.
The PowerPax DCC Programming Booster by DCC Specialties is an older design and may not work with all decoders and command stations. There are timing differences which may be an issue as well. Soundtraxx's PTB-100 was designed when programming sound decoders became an issue, and addresses the timing problems.
Soundtraxx Tsunami2 and Econami Series DCC Decoders
The Sountraxx Tsunami2 (TSU-2) and Econami series of decoders do not require a programming track booster. Users have reported that attempting to program the TSU-2 or Econami decoders with a PowerPax gives erratic results.
Previous Tsunami sound decoders required a program track booster.
Video: Wiring a Program Track
Video: Build a Portable Program Track
Building a Standalone Portable Program Track
- Decoder Programming - Additional information about programming decoders
- Track wiring - Track wiring
- PTB-100 - Programming Track Booster by Soundtraxx.
- Decoder Tester - Apparatus for testing and programming decoders.
- Note about using a programming track booster with NCE Powercab. (NCE Website)
- NCE Auto SW