How to Build an Electronic Steam Engine Sound Circuit

By Liz Frazier ; Updated April 12, 2017
Model trains with electronic sound circuits are fun both to build and to watch.

In the world of model railroading, adding an engine sound such as a train whistle is a great way to bring your set alive. Fortunately, the electronic circuitry behind an authentic-sounding train whistle is relatively simple and requires only a basic understanding of electronics and soldering. By learning how to assemble this circuit, you can add just that extra touch your model train needs to go from ho-hum replica to a dynamic showpiece fit for any scale-model station or town.

Connect the NE556 integrated circuit to the center of the breadboard. This chip has two rows of pins. Orient the chip so that each row sits on either side of the center gap that runs down the middle of the breadboard.

Connect pin 14 to the 9-volt power bus strip (+9V).

Link pins 13 and 14 with a 68-kiloohm capacitor.

Link pins 8 and 13 with a 33-kiloohm resistor.

Link pins 8 and 12 with a jumper wire.

Connect a 47-nanofarad ceramic capacitor to bridge pin 12 and the ground bus strip (GND).

Connect the anode of a 100-microfarad/16-volt electrolytic capacitor. Connect the cathode of this capacitor to the 8-ohm loudspeaker. Finally, connect the loudspeaker to GND.

Bridge pin 3 to GND with a 100-nanofarad ceramic capacitor.

Use a jumper wire to link pin 7 to GND.

Use a jumper wire to connect pins 4 and 14.

Bridge pins 1 and 4 with a 390-kiloohm resistor.

Use a jumper wire to connect pins 1 and 2.

Bridge pin 2 to GND with a 2.2-microfarad/16-volt electrolytic capacitor. Orient the capacitor so that the positive anode is connected to pin 2.

Bridge pin 13 to pin 5 with a 33-kiloohm resistor and a 1N4001 diode. Orient the diode so that its anode is connected to pin 5.

Bridge pins 5 and 10 with a 1N4001 diode.

Bridge pin 10 to GND with a 4.7-microfarad electrolytic capacitor. Orient the capacitor so its anode is connected to pin 10.

Bridge pin 10 to GND with a 68-kiloohm resistor.

Connect a 9-volt battery to +9V and GND with a 9-volt battery clip.

Things Needed

  • Breadboard
  • Jumper wires
  • 1 resistor, 330 kiloohms
  • 1 resistor, 390 kiloohms
  • 2 resistors, 68 kiloohms
  • 2 resistors, 33 kiloohms
  • 1 on/off switch
  • 1 reed relay
  • 1 NE556 integrated circuit
  • 2 diodes, 1N4001
  • 1 electrolytic capacitor, 4.7 microfarads/16 volts
  • 1 electrolytic capacitor, 2.2 microfarads/16 volts
  • 1 ceramic capacitor, 100 nanofarads
  • 1 electrolytic capacitor, 100 microfarads/16 volts
  • 1 ceramic capacitor, 47 nanofarads
  • 1 loudspeaker, 8 ohms/0.25 watts

About the Author

Liz Frazier has been producing Web content, instructional articles and trivia for websites such as TopTenz.net and RealDealTechnologies.com since 2008. Her writing interests lie primarily in the areas of politics (specifically public administration and elections), the military, education and forced migration. Frazier has a Bachelor of Arts degree in political science from California State University, Northridge.