Section Indication For Model Railway

EE JULY/AUGUST 1987 16 By E J Carroll This section indication system may be a just the thing you have been looking for when you own a fairly large model railway with tunnels and tracks at several levels, and are sometimes at a loss find the wherabouts of a particular train. This circuit uses LEDs to indicate the train"s position. Each track block is split up into 8 sections, whose starting points are marked with reed contacts (Si-S8). A ninth reed contact is fitted at the end of the block, to enable turning off the indication for the rel- evant length of the track. The circuit is composed of 8 set-reset (S-R) bistables, which drive a LED each. All SET inputs are combined in a NOR gate, Ni, which drives a pulse shaper and buffer to reset the bistables with a brief pulse to ensure that only the LED for the last passed track section is lit. The reed contacts are actuated with the aid of a small magnet fitted to the underside of the engine. Depending on the most suitable location of t...