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A reed switch buried under the sleepers will complete a circuit when a magnet glued to the loco's underside passes over it. This triggers the delay I.C. giving a output to drive the transistor. This can pick a relay or other logic circuitry. The Output remains low until the delay times out. This depends on the value of the capacitor, roughly 1.2 seconds per 1.0ufd. A change of the 1m0 resistor to 10 megohm can also be used to extend the delay. Useful for signalling, road crossing lights and bells etc. The LED is not needed but is an indicator of the delay time when testing.
A reed switch buried under the sleepers will complete a circuit when a magnet glued to the loco's underside passes over it. This triggers the delay I.C. giving a output to drive the transistor. This can pick a relay or other logic circuitry. The Output remains low until the delay times out. This depends on the value of the capacitor, roughly 1.2 seconds per 1.0ufd. A change of the 1m0 resistor to 10 megohm can also be used to extend the delay. Useful for signalling, road crossing lights and bells etc. The LED is not needed but is an indicator of the delay time when testing.
LINK TO IMAGE - det-reed.gif
Circuit Schematic
