Tapiola Parish Model Railway Club

Signalling logic, slow motion light signals

The small staton has limited CMOS logic "interlocking": one can get only one starter at each end green at the same time and only one home signal may be green at one time. The light change slowly and like the real thing the red light dimms out and only after it has goen out completely will the green light brighten up. The home signals are not yet fitted as we have not yet resolved the best way to fit them to modules (the home signal could be at any module).

Signal mastheads (for DIY-signals):

• Masthead_H0_N.pdf
• Masthead_H0_N.cdr

The other end of the big station has the same features, but they are microcontroller driven. A PIC16F84 processor operates three starters, home signal and distant home according to points settings. All the signal's LEDs will go on and off slowly. This is done with PWM incorporated within the PIC. The signals are operated with three position toggle: in mid-position all are red, if turned outward the correct starter will show green and if turned inward the home signal will show green. the correct starter is picked from turnout position feedback. There is a provision for a single train detector to sense the area between starters and home (the pointwork and part of the line) and in case a train is found there it will automatically put all signals to red. the control switch must be reset in order to get next green.

The assembler code was coded using finnish variable names and all comments are in finnish. I'm trying to get the code "translated" into english, but this may take some time. The beginnings are found below:

OP_4.ASM

Orignal code, comments and variable names in finnish

OP_4_eng_B.asm

Translated to English to aid following the code (updated in 2022-04-17).

Signal masts are to be fitted to modules close to stations or at locations where block signalling is needed. The layout is provided with "sockets" or "foundations" for signals:

Due to modular design the signal mast foundations are needed at every module. Hence the foundations have been designed to be simple to make and install (just a 5 cm length of 10mm outer dia. 8 mm inner dia. water pipe.

Serial transmission of data between control panel and layout

A time base module is to be connected between layout modules and control panel modules. It will generate the timing pulses and cross connect the data in and data out lines and count the clock pulses needed between strobe pulses:

kelt.gif

The 8 bit module. The unused pins of RJ-connector are used for power transmission (filtered 5 volts). The pins are chosen so that each signal becomes twisted with one of the power feeders and as the power consumpton of modules is low this is hoped to reduce transmission errors.

This setup has not been tested in "real life" and still a project under development! [Actually project cancelled]