KB537: DN142 - Turning on Back EMF

This article was last updated on Aug. 17, 2011, 7:52 p.m. | Print Article | Leave Feedback

The DN142 comes from the factory with BACK EMF SPEED STABILIZATION (BEMF) turned off.

Follow this procedure to turn it on and to adjust it. Later generations of Digitrax mobile decoders do not require this procedure.

: To activate the BEMF feature, change CV57 to a value of 06. This will give good performance with most brands of locomotives.

If the locomotive surges while using BEMF use a lower value for CV56.

It may also be necessary to adjust CV's 55, 56, & 57 to get the motor performance desired for your particular locomotive.


1. Program CV57 (Droop control) to a value of 005. This will turn on speed stabilization.

2. Put the loco on level track and run it at about 20% of full speed. In Program Mode increase the value in CV55 (Static) from the default value of 128 upward until you observe the loco jumping as speed steps increase. Finish this step by programming CV55 to the value that is 1 less than the value just before the jumping motion was observed. Note: OPS MODE programing on the main line works very well here.

3. Follow the same procedure with CV56, beginning with the default value of 048 and increasing it until you notice the loco oscillating, faster-slower, faster-slower, as speed is increased. Finish this step by programming CV56 to the value that is 1 less than the value programmed just before the oscillation was observed.

4. Follow the same procedure with CV57, beginning with the value 005 as programmed in step 1. Increase the value for CV 57 until the speed when going up hill is roughly equivalent to the speed on level track. This will yield a best droop consistent with the locomotive characteristics.

5. Keep notes about the CV values you program for these 3 scaleable speed stabilization control CVs so that you can use them as a starting point for setting up scaleable speed stabilization in similar locomotives.

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