Grade Crossing Bell Ringer Circuit

28 June, 2021

  This circuit is a driver for a mechanical - Grade Crossing Bell Ringer - that was originally built for the London Model Railroad Group.

  The circuit can be used to drive a Heath/Zenith Model 172C electric bell.

  Model 174C electric bell.


  RINGING RATE - The ringing rate of the bell is adjustable between approximately 1 ding per second to 4 dings per second.

  SOUND - The sound is reasonably loud and mechanical sounding, similar to actual crossing bells.

  The sound can also become quite annoying. A switch in power supply to the ringer circuit is recommended so that the bell can be turned off.

  CIRCUIT CHANGES - The value of R4 can be lowered and the value C4 increased to give a more powerful coil current if a louder ring is desired.

  BELL MODIFICATIONS - The contacts that break the circuit of the bell's solenoid are not used and are bypassed by connecting the blue wire directly to the coil. The armature may also need to be reshaped so that less throw is required for the hammer 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


Bell Ringer Circuit Parts Placement Diagram

Bell Ringer Circuit Parts List (2019)

Qty   Circuit Part Number   Part Description   Digi-Key Number
1 - IC 1 - LM555 -
1 - Q1 - TIP120 - TIP120-ND
2 - D1, 2 - 1N4001 - 1N4001FSCT-ND
- - - - - - -
1 - R1 - 10K 1/4W - 10QBK-ND
1 - R2 - 1M Potentiometer - 3306F-1-ND
1 - R3 - 2.2K 1/4W - 2.2QBK-ND
1 - R4 - 330 Ohm 1/2W - 470KH-ND
- - - - - - -
1 - C1 - 33uF - P5180-ND
1 - C2 - 1.0uF - 399-6596-ND
1 - C3 - 1.0uF - 399-6596-ND
1 - C4 - 470uF/35V - P5168-ND
- - - - - - -
2 - Terminal Block - 2 Position, 3.5mm. - ED2635-ND

Go to the 2011 - Automatic Grade Crossing Circuit

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Please Read Before Using These Circuit Ideas

  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.

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28 June, 2021