Disneyland Mark VII Monorail - soft start / stop

The Mark VII remote works well but it always bothered me the way the monorail starts and stops so abruptly, jostling all those HO scale passengers around.  It's bad enough with the original (slow) drive system but it is obvious with WhisperJet as the monorail really jumps into motion!  I installed a soft start for my own Mark VII to enhance the realism and thought others may be interested in this feature. 

Since I was installing the auxiliary motor controller to get more power to the motor *and* since I was installing a 3.3 V converter to power the white LED headlights it was only a few more wires to also install a microcontroller to control how quickly motor power is ramped up and down.

And since... no, I stopped at that point.  ;)  Now the Mark VII accelerates from zero to full speed over 3 seconds (adjustable) and slows to a stop at the same rate, much smoother!  It is nice to see the Mark VII with realistic headlights and operation, all using the original  remote control.  If the STOP button is pressed before the monorail has reached full speed it decelerates from whatever speed it has reached. If the monorail is running and the opposite direction is selected it slows, stops, and then reverses direction, smoothly!

When the power is switched on the headlight blinks three times to verify the system is ready.

And no, I didn't quite stop there: it only took a little more programming to have the headlights flash a warning pattern when the monorail is in reverse.  :)


Technical details: in the original circuit the remote circuit board connects to the motor with BK and BR wires. In FWD BK is connected to B+, BR to B-. In REV it is the opposite. In STOP both wires are disconnected from the batteries. The new circuit is similar to my motor upgrade plan for the Mark VII with a twist: instead of the BR and BK wires directly connecting to the new motor controller the signals go to a microcontroller that ramps up/down the power over a few seconds. The new ramped signal then goes to the motor controller.

Along with the DRV8835 motor controller board we now have a PIC 12F1572, programmed to provide soft start. We also have a 3.3 V converter to power the PIC and the white LEDs. The parts are not expensive, it's the wiring and programming that takes a lot of time and effort. I can provide programmed PICs if anyone is interested in trying this on their own.

The PIC has three PWM (pulse width modulation or speed control) channels so after I used two to control the motor there was still one left over to control the headlight! The headlight is on in FWD but flashes as a warning light in REV.

The usual problem of where to put everything gets even worse but the PIC is now at the rear of the monorail where it is accessible to make changes in the programming (which actually means swap the PIC for a new one since they are inexpensive).