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Eric's Tech for custom speed tables w(slash) Commander

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  • Eric's Tech for custom speed tables w(slash) Commander

    In the spirit of getting some non-controversial and helpful content here, I’d like to share a technique I used to help me set up some speed tables with my Atlas Commander. It came about from a discussion on the Atlas board. I’m sure it’s not unique, but I hadn’t run into it before.

    Background: The Atlas Commander doesn’t display the current speed step it’s sending to a given decoder (i.e. #3 of 28). I figured that if I knew the speed step I was in I could shorten the trial and error needed to set up custom speed tables or Vmin/Vmid/Vmax. I was worried that just taking a protractor and marking equal ranges around the control knob would not necessarily map to the various speed steps.

    The Plan: Take a piece of stiff paper or thin cardboard and cut a 1-3/4” diameter hole in it for the control knob. Trim the paper so it fits over the knob and fits tightly inside the side-wings of the Commander. Program a decoder to have a custom speed table with alternating on and off steps. I used: 33, 0, 33, 0…. Make sure Vmin, momentum, etc. are off. Using this decoder, very slowly turn the control from OFF to MAX. Each time the locomotive starts or stops make a mark on the paper. The spaces between the marks indicate the various speed steps. Reset the decoder. You now have a speed step template to put over the control any time you need it.

    Result: The Commander control is pretty linear with respect to the individual steps, but with significant larger areas mapping to OFF and MAX at either end of the control. This seems like a good idea – you want anything near OFF to be OFF. Those train set guys probably want MAX to be MAX too!

    There is a little bit of slop in the control, but positioning the knob in the middle of the indicated range for a given speed step does give reproducible results. Also, I only did this for 28 steps – so a touch of math is required to figure out what numbers to shove in the CVs. Or you could use one of the spreadsheet speed table generators that are out here on the net.

    It still took longer than I thought to zero in on the value I wanted for Vmin, but it sure was nice knowing that I was in speed step #1.

    Thanks Paul Rahman and TomasSz for the help and hints.

    The original discussion can be found at: