Spreadsheets and DCC

Update 16 April 2009: I’ve added a link to the TCS spreadsheet.

I don’t have any kind of fancy programmer for my DCC decoders. I have only a Digitrax Zephyr, and the will to enter dozens of CVs by hand. I don’t have the money to do more than that. I am willing to bet many of my readers are in the same boat.

Well, just because we don’t have fancy computer-controlled programmers doesn’t mean we can’t take advantage of our computers! To that end, I’ve put together a fancy spreadsheet to help manage the CV settings of my various trains. I’m doing one spreadsheet for each major manufacturer (because they all do things differently), and you can download the Digitrax spreadsheet here and the TCS spreadsheet here. Read on for instructions.

(A note! This spreadsheet is for Apple’s Numbers, which is Mac only. Some of the functions I use apparently are not supported by Excel. I don’t have a copy of Excel to even check this. If anyone could help me translate this spreadsheet into a more universal format, the help would be greatly appreciated).

How to use this spreadsheet:
The spreadsheet has two pages. The first is for tuning the speed of locomotives or motor cars. This is especially useful for speed-matching your model to the prototype, or to another model for consisting. The second page is for calculating and recording the CVs for any kind of Digitrax decoder. I’ll start with the first page.

Scale Speed Trials

First, we’re going to figure out how fast the locomotive or motor car is going at different voltage levels. If you are setting up a cab car, you can skip these steps.

Begin by setting up BEMF according to the instructions here. Different values for CVs 55, 56, and 57 can affect the top speed of your locomotive, so it is important that BEMF is set up properly first. If you ever change the values in these CVs, you will have to re-do the next few steps.

With that out of the way, set up an oval of track. We’re going to time the locomotive at a fixed voltage to determine the speed. You’ll need to know how long this oval is: There is a calculator to help you figure that out on the first page of the spreadsheet. Now, set Vmid (CV 06) to something low, like 3. Pick a Vmax to test. Start with 255. Everytime you test a new value, create a new row in the “Time Trials” table. Make sure to keep the voltage values in order from lowest to highest. Run your loco at full throttle for a number of laps, and time the run. Record the length of the oval, the number of laps, and the time in the “Time Trials” table. The table will tell you how fast your locomotive was travelling in scale km/h for the voltage level you set for Vmax. Do this for several different values of Vmax, and you will see the graph interpolate the speed at other voltage levels. There’s no need to test at all voltage levels; 4 or 6 will suffice.

Calculating and Recording CVs

Now. Go to the second page. All the CVs listed are filled in with the default values. The graph on the right will help you determine values for Vmin, Vmid, and Vmax (CVs 2, 6 and 5) that are prototypically accurate (assuming you know how fast the prototype travels). Alternately, if you want to use the advanced 28-speed-step table, you can enter values into CVs 67–94. The graph will reflect both methods. Enter acceleration and deceleration values into CVs 3 and 4; the sheet presumes you are using the 3-speed-step table for the purposes of calculating actual accelerations.

Finally, if you need to calculate a 4-digit address for manual entry, type the desired address under where the table reads “Type a 4-digit address”. CVs 17 and 18 will be automatically calculated for your convenience.

Don’t forget to set CV 29!