Train decoder for Märklin Digital

There is an error on the PCB for Frankies booster, on Frankies webpages.

Please use this corrected version.

This design is an expanded version of Märklins popular Delta decoder.
In addition to understanding both old and new formats,
it also has output drivers for four extra-functions and the AUX-function.

Change in component values December 7, 1999
Latest news and development history
Version 2 AC details
Download HEX-files
Download layout files (postscript format)

The main features are:

  • On-track programming of all parameters.
  • User-defined speed characteristics (speedtable).
  • Start/stop delay from 0.5 sec. to 38 sec. in 0.5 sec. steps.
  • 128 internal speedsteps.
  • 27 speedsteps with modified Märklin/Motorola format.
  • All functions available as outputs (Func, F1 - F4).
  • Seperate output for lights (direction dependant).
  • F4 can be used to switch the delay on/off if desired.
  • F3 can be used to switch between normal and shunting speedtable if desired.
  • F3 can be used to switch speed-dependant steam on/off if desired.
  • Output for AC and DC motor.
  • Secondary address. Can be turned on/off during on-track programming.
The decoder will NOT work on analog layouts.

How it works:

The heart of the decoder is a PIC16C84 chip containing software for decoding the track signal and controlling the motor and the accessories.
The decoding of the digital signal from the track is made on the basis of the fantastic document by Andrea Scorzoni: The manual of the new Märklin-Motorola format.
So in addition to understanding the new format, the decoder also uses the information contained in the new format, in particular the absolute direction information.
The direction is stored in nonvolatile memory, so the decoder doesn't forget this info when power is removed. Especially important for those using the old format only.
Max. motor current 1A, max. current for F1 - F3 is 1A each, max. current for AUX is 200mA. The total current must not exceed 1.5A, as this is the rating for the diodes in the rectifier bridge.

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(C) 1999 Bo Brændstrup