This circuit controls a Search Light type signal head and produces solid - RED, YELLOW or GREEN indications.
This circuit uses a LM556 - Dual Timer IC in a complimentary output configuration to drive a red and green, bipolar light emitting diode to produce the three signal output colours.
The circuit can be used in a Normal or Approach lighting mode for the GREEN signal. If Approach lighting is not needed, the parts used for this can be left off of the circuit board and pins 4 and 10 of the 556 timer connected directly to the supply voltage.
The next diagram shows five signal block circuits connected using the terminal blocks mounted on the circuit boards. A four conductor cable could be used to connect the individual blocks together.
Any number of blocks can be connected together.
Block Occupancy Detectors could use the same power supply as the signals and can be located near the signal controller boards.
The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.
If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.
Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.
11 November, 2011