5. The LED above shows the state of the relay. When
the relay is open (off) the LED is off. When it is closed
the LED is on. An LED of any color or size can be used.
This unit also makes an ideal point-to-point controller for a
trolley or small train. Adding diodes at each end of the track
creates two sync points that can provide a very repeatable
sequence of movements with an almost unlimited number of
station stops, pauses, reverses, and so-on.
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