Model Scenery Tutorials

A Comprenshive Modeler's And Model Railroader's Guide

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Model Railroad Block Signal Driver For Three Aspect, Two Aspect And Spotlight Signal Lights

A review of the Model Scenery Block Signal Driver with specific callouts to instructions on how it is used to satisfy specific requirements.

The Circuit Can Be Used To Drive

  • Red, Yellow and Green – 3 Light signals.  Click For Instructions
  • Red, Yellow and Green – 1 Light signals. Click For Instructions
  • Red and Green – 2 Light signals. Click For Instructions
  • Red and Green – 1 Light signals. Click For Instructions
  • PRR Position Light signals. Click For Instructions

Model Scenery Block Signal Driver Features

This is a list of the features. How they are used  is covered in specific tutorials that are part of this series

  • Block occupancy detector inputs are low current and are not voltage sensitive.
  • Complex signal arrangements are possible by adding diodes at the block occupancy detector inputs.
  • The signal light LEDs can be connected either common cathode or common anode.
  • The signal drivers can be connected for NORMAL or APPROACH lighting of the GREEN signal.NORMAL Lighting means that the GREEN signal is always lit unless the signal is changed to YELLOW or RED by one of the circuits inputs.APPROACH Lighting means that the GREEN signal is onlyon when the block before a particular signal is occupied and thus showing a RED signal.
  •   The signal circuits can be controlled by any device that can pass at least 1 milliamp current and shares a common connection with minus terminal of the signal circuit’s power supply.
  •   The circuit is designed for a 12 volt power supply voltage and will drive light emitting diodes at approximately 10 milliamps. Other supply voltages and LED currents can be used.
  •   The values of the current limiting resistors for the LEDs can be changed to achieve the desired brightness
    from each signal LED. For example;- If the signal LEDs are too bright, external resistors can be connected at the circuit board’s outputs rather than replacing resistors on the circuit board.- If the signal LEDs are too dark, resistors can be replaced with resistors of lower value.
  •   Diodes  at the base circuit of transistors provide an extra voltage drop in the base circuit that allows
    the transistors to turn off completely.
  •   The combined current from a DETECT INPUT of one block and the YELLOW INPUT from the previous block is about 2 milliamps.This low current allows the PNP signal circuit to be controlled directly
    by optoisolators.
  •   The circuit’s Block Occupancy Detector input will operate at properly at voltages of less than 3 volts.
  •   More than one block can be controlled by a single input device if diodes are used to separate block input devices such as occupancy detectors, toggle switches and computer control systems.
  •   The signals can be controlled by a dispatcher using toggle switches. In this case no occupancy detectors would be needed.The toggle switches can be used in conjunction with block occupancy detectors.
  •   Common cathode and common anode connected LEDs can be used for different blocks so that various home built and commercial signals could be used at the same time.
  •   The circuit can be adapted to drive 2 colour, common cathode connected or common anode connected LEDs to make a Search Light type signal. Diode.

About The Driver

 

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