This is an updated version of an LM555 timer based – Grade Crossing Bell Ringer – circuit that was built for the London Model Railroad Group.
SOUND – The sound is reasonably loud and mechanical sounding, similar to actual crossing bells.
CIRCUIT MODIFICATIONS – The value of R1 may be lowered and the value C1 increased to give a more powerful coil current if a louder ring is desired.
BELL MODIFICATIONS – The circuit-breaking contacts of the bell’s solenoid are not used and have been bypassed by connecting the blue wire directly to the coil. The armature has been bent so that less throw is needed for it to strike the gong.
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