ESU Essential Sound Unit Speed Matching With JMRI

Speed matching an ESU Essential Sound Unit is a little different since it does not support CV6 which is the mid-point of the 3 point speed curve. See figure 1. 

                                      

Figure 1 3-Point Speed Curve

This means you are forced to use the Speed Table shown in figure 2.

Figure 2 Speed Table

Using the Speed Table requires that you have CVs 2 and 5 set to the values you require before adjusting the mid points. Why this is necessary is discussed in this post in the ESU section.

This can be a time consuming task but in this case there is a way to drastically simplify setting CV6 using JMRI. Speed step 14 is the equivalent of CV6 so, adjusting it would simulate adjusting CV6. The problem becomes setting the rest of the speed steps. Technically CV6 lies between speed step 14 and 15 so you can use the one you prefer. 

As long as you have a good linear motor in your locomotive there is a shortcut here. First check the Use Table radio button at the top of the table , if necessary, click the Force Straight button to straighten out the curve. Than mark the checkboxes just above the buttons for Speed Steps 1, 14 (or 15), and 28. See figure 3.

Figure 3 Speed steps checked

Now let's say we need to decrease CV6 on this locomotive to match the speed of another locomotive. Remember, you always match to the slowest locomotive. Click and hold the slider for CV14 and pull it down to the value you want which is displayed at the top of the slider. See figure 4.

Figure 4 Adjusted speed steps

<Note>

The change made in figure 4 is quite the drastic change and it is only shown to demonstrate what you can do. It is quite doubtful you will have to change things this much.

Notice how the other sliders, both above and below the one you changed, follow in a linear manner. That's the shortcut! Now, write the entire sheet to your locomotive and test it. It now becomes a repeat operation until you get matched speeds. This can be done on a test track or "On The Main". Again, your call. If you compare this procedure to figure 1 you can see it's the same result.

Hopefully, you find this to be much easier and also quicker to implement.

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