SHUTTLE_TRACK_CONTROLLER

Published:2009/7/17 3:36:00 Author:Jessie | From:SeekIC

This circuit enables a model train to shuttle continuously between two tracks. When the train travels from left to right across the track in the lower part of the diagram, the lower rail (D) is connected to the positive supply line. After it has passed diode DB, the train will stop. Because the loco-motive short-circuits the diode when it passes the break in the rail, a short positive pulse is generated on rail section B. The pulse is used to set bistable IC1, whereupon D3 goes out and capacitor C3 is being charged. When the potential across the capacitor rises to a sufficiently high level, transistor T1 switches on, whereupon the relay is energized. This causes the polarity of rails C and D to be re-versed. Diode DB is then on, so the train departs in the direction of A. Rail C is then connected to the positive supply rail; so when the train passes diode DA, a positive pulse is generated on rail section A. This pulse is used to reset the biastable, whereupon the LED lights and the relay is deenergized. After the relay contacts have reversed the polarity of C and D again, diode DA comes on and the train departs again in the direction of B.



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