In these circuits a transformer is used to isolate the detector circuitry from the track power circuit. The circuits have been designed to use a minimum of parts and to take their operating power from an external power source supply.
The circuits on this page are for use with DCC systems only.
NOTE: The detection sensitivity can be increased by adding turns to the primary side of the transformer.
The 339 comparator based circuit has an open collector output that can sink up to 20 milliamps.
The 555 timer based circuit has an open collector output that can sink up to 200 milliamps and a bipolar output that can sink or source up to 200 miliamps.
Also see Dual - Transformer Type Block Occupancy Detector For DCC.
A suitable, low cost transformer is available from Surplus Sales of Nebraska . The part number is Vitec Transformer - (TM) 57P1822G
Another suitable transformer is available from Jameco Electronics part number is 164718PS (Original part number MTC 30101)
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.
06 January, 2011