DCC Controller and Decoder Explained

The description has been kept as generic as possible to allow user to relate to different brand of DCC Controllers and Decoders

The minimum equipment that you require for a DCC layout is a Digital Command Control (Cab/Cabin Controller) and the Decoder chip fitted on a locomotive.

The Function of the Cab Controller is used to supply commands to the decoder chip which forms part of the locomotive. The commands can be Forward/ Reverse direction, turn the Head and Reverse lamps On and Off (basics functions). The Cab Controller also can be used to program a locomotive to perform in a certain way. Main line locomotive viz-a-viz a shunting locomotive will behave in a certain manner in real life scenario. The cab controller all the user to adjust the values on the Decoder to allow the model locomotive operate or perform in pro-typical manner ( pro-typical = something equal or closer to the original equipment. In our case we are trying to replicate the functioning of real life locomotive to its scale model)

DCC/ Command/ Cab Conroller Cab stats for Cabin and is referened to the Locomotive cabin where all controllers are set
DCC Decoder Chip. This is the chip that goes into the locomotive. The wires are color coded and have specifc purpose. Example While is for front head light and Yellow for Rear Head light.

The Decoder chip is a small PCB board size of a postage stamp (varies from manufacture to manufacture). The Decoder has minimum of 7/8 connections.
2- for track pick up (power)
2- for feeding power to the motor
1 each for Head and Reverse lamp
1 common for accessory power
2- optional for additional accessory functions
Each wire has a industry standard color code (NMRA standards) which results into consistency been maintained across different manufactures. This includes connectors and plugs.

Difference in DCC vs DC

To a person who is new to this hobby. I explain this the following ways.

In a DC setup, if you have two or more locomotive on a single straight track, then when you power up the track all the locomotives will start moving (the direction is not important here). In a DCC layout. The same set of locomotives now equipped with the DCC chip and operated by a Cab Controller would allows the user to independently start each locomotive separately. This is done by selecting a number on the Cab Controller which related to the locomotive and then increasing the throttle. So the locomotive which which received the command will only start moving. Similarly for second locomotive only the lights can be made on/ off while the first locomotive continues to run. Note all locomotives are on same straight track.

Moving further to into the decoder programming- A factory installed decoder is programmed for optimal functioning and may not require any programming. But once you start collecting locomotive of different types (main line or shunting locos/ steam) and use a standard decoder from a one manufacture like Hornby Bachmann, MRC, NCE then, you will observe that all the trains will behave in same manner. This is where the programming of the decoder kicks in as you can configure the working of the loco based on the types mentioned above.

Each decoder comes preprogrammed with a default short address of 3 (NMRA Standard). However, in order to personalize your locomotive, e.g. use a speed settings long address that matches you locomotive type or enable special lighting affects, more work is necessary. The work comes in the form of programming the decoder, or basically changing manufacturer-provided configuration variables (CVs) to match your specific needs. Please note that not every decoder has every CV on each and every decoder, however, there are a series of base CVs that must be made available by the DCC decoder manufacturer in order to meet the NMRA guidelines to provide portability between the various DCC system vendors.

Decoders can be programmed in two mode, Service or Main tack programming, again each Cab Controller manufacture may call this different, but the underline principal remains the same as as explained below In Program mode, also commonly referred to as Service track programming, the main layout power is disconnected and no trains can be operated. It is in this mode that you must have only one decoder-equipped locomotive on the dedicated programming track or the whole layout. In Ops mode, also commonly referred to as Main track programming, you can have multiple locomotives on the track all receiving power. But when you select a particular locomotive address and then pass on the CV value, the selected locomotive will receive the value, other locomotive will ignore this CV value.

Before you begin programming, it is always a good practice to have the decoder manufacturers instruction sheet sitting next to you while programming your decoder as it contains a list of all the available CVs and their respective default. While programming some common CV's across manufactures, you can refer any manufactures manual to know the function of the CV, but the value range may be different for each manufacture. The most important thing to know is the factory reset CV number and the value for it. So even if you make an mistake in programming, you and blindly reset the decoder to the factory default address 3 and then rest start programming. If you do not have this, then you can alway google to find the rest CV number and Value for a particular manufacturer.

So to start with, we are going to start with simple programming. We will use the Service track programming as it is safer compared to Main track (my view) To keep this document generic I would suggest that you use your Cab or Command Controller user manual to refer to the functions or to enter into a certain programming mode.
So minimum hardware require
Cab / DCC/ Command Controller (whatever you would like to call this)
A DCC equipped Locomotive
A track on length no less than the length of the locomotive
1. Connect the Controller as explained by the manufacturer
2. setup the locomotive on the tack
3. power on the Controller
At this point your locomotive should slightly jerk or the lights may come on momentary (no necessarily)
If this is out of the box locomotive then it is 100% that the locomotive address will be 3. Select the number 3 on the controller and press the relevant key (ok or select) if you have a controller with a LCD display then the number 3 should get displayed. At this point your locomotive would be read to receive commands from the controller. Use the forward/ reverse or the light function to see if the locomotive is responding. If it does then we are good to go.

  • First simple programming is to change the address of the locomotive CV1 (common across all manufacturers)
  • Refer to the user manual to see how to enter the Service track programming or the Program Mode.
  • Once you are able to identify the the keys to reach to this mode. You will be prompted to select the CV.
  • Type the CV number =1. Then you will be prompted to enter the value.
  • Type number 4 (or any other number other than 3)
  • Use the appropriate key (OK or Select) to send the command to the locomotive
  • At this point the Locomotive should jerk a bit or the lights will flash or a second (if equipped with lights typically diesel locomotives)
  • This tells you that the decoder chip on the locomotive has accepted the command.
  • Now come out of the programming mode and if the LCD shows the number 3 then try the light function or the throttle to see if the
  • locomotive moves. If it doesn't then the programming has worked.
  • Now select the address that you had entered example 4.
  • Now again use the ight function or the throttle to see if the locomotive moves. If it move, then congratulations as you are in business as you have taken first step towards programming.

The next two or three CV's that you can program are the CV's 2, 3, 4

  • CV2 is for start voltage
  • CV3 for Acceleration
  • CV4 for Deceleration

These three CV's are going to impact how the locomotive will move ahead or start or stop post the throttle is increased or decreased. I will let you experiment on this. You can always go back and reset the decoder to factory default or replace the each CV vale to factory default (each manual will come with the company default setting for each CV)

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