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Jonathan Scotts P684SV Train Controller


P684SV Train Controller

At right you see a picture of the mains-powered version of my new top-of-the-line model train controller, the P684SV. The comprehensive and realistic UserReferenceManual-PID684SV is available in PDF format.

This controller has the following features:

  • Precise speed control delivered by full Proportional-Integral-Differential feedback regulation of engine RPM (engine back EMF);
  • “Analog Waveform Drive” to give the precise control of digital PWM with the gentle action of traditional, fully-analog drive voltage, to guarantee that locomotives are not overheated;
  • Shunt (center-off) and Cruise (anticlockwise off) modes to suit layout;
  • Factory presets of control algorithm coefficients, inertia, braking strength, auto-stop distance, timeout interval, and motor heating estimation constants for Z, N, HO, O and G scales;
  • Coasting and braking for realistic driving;
  • Reversing at speed is impossible;
  • Adjustable simulated inertia, and an override switch to disable inertia for setting up;
  • Adjustable braking capability;
  • Operational condition indication by flashing LED or panel meter;
  • Station stopping with constant-distance pull-up (“ABS”);
  • Automatic station stops with and without reversing, for automation of layouts;
  • Indication of peak or average load current, engine RPM, instantaneous thrust, or engine temperature;
  • Timeout mode (“dead man switch”) to halt unattended trains;
  • Overload protection.

The controller is also designed to allow a simple panel-mount design, shown here.
The PCB layout is shown at right and the circuit diagram is below.

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