This is an updated version an LM555 timer based - Grade Crossing Bell Ringer - circuit that was built for the London Model Railroad Group. The circuit drives a warning bell that is shown on the page.
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.
Home Depot carries a bell in their electical section that is similar to the one shown on this page. The model number is 172C and the stock number is 106 419
The bell is made by Heath/Zenith and can be seen at this link - Model 172C electric bell.
Heath/Zenith also make one with a larger gong - Model 174C electric bell.
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.
23 October, 2008