Squealer User Manual ¶

Overview¶

The Squealer is a true motion-detecting flange squeal system. Using professionally recorded and edited flange squeal, the Squealer brings authentic trackside sound of steel wheels against rails for ultimate realism. The system uses a micro motion detector between the ties to sense train movements and play either the built-in professional sounds or user-defined sounds for maximum flexibility. Modelers now have the ability to recreate all the trackside audio ambience that has been missing from our model worlds.

Placed in locations on the layout where flange squeal is most likely to occur, the Squealer takes the immersive layout experience to a new level. Use individually (with one or more sensors) or place several Squealer systems together to get an all-encompassing stereo effect. The professionally recorded and edited built-in sounds provide a basic sound landscape for most situations, but custom sounds can also be loaded using a microSD card. The possibilities are only limited by your imagination!

Features¶

True motion-detecting operation: only squeals when something is moving
Simple, discrete under-track installation
Professionally recorded and edited flange squeal sounds play randomly
Sounds fade smoothly when activated or deactivated
Custom sounds can be loaded using a microSD card
Comes complete with sensor, speaker, and control board
Powered from 5V to 24V DC
Additional motion sensors available

Typical Applications¶

Mainline curves
Yards
Tight industrial trackage

Quick Start Guide¶

Power¶

The Squealer can be powered from 5V to 24V DC, applied through connector J1 (positive to VIN, negative to GND). Alternatively, the mini USB jack can be used to power the Squealer, either from a USB charging block or a laptop/PC.

Sensor Installation¶

Drill a 1/16" pilot hole down through the benchwork
Drill a 3/8" hole up to just under the ties
Align the motion sensor with the top of the ties. Use a piece of paper towel or tapered shim and gently wedge into the hole to hold the sensor in place

The motion sensor is powered from the Squealer board. The red wire from the motion sensor connects to J2 in any of the RED terminals. Similarly, the black wire from the sensor connects to J3 using any of the BLK terminals. The sensor output wires (white and blue) connect to IN1 and IN2 terminals on J4 respectively. Note that the center terminal on J4 is ground and shouldn’t be used.

Position the sensor below the rail even with the tie height. Make sure the full face of the emitter opening and imaging array is clear of any ballast or obstruction.

Although the sensor and the control electronics are relatively robust, standard precautions should be taken — avoid static electricity, don’t let it get wet, and keep conductive materials away, etc.

Additional sensors may be connected the same way as above. Terminals IN3 and IN4 can also be used for the sensor output wires (white and blue) if more space is needed. Although a large number of sensors can be connected to one board, practically speaking, four or five is probably the most that make sense in most situations since you want the speaker to be reasonably close to where the sound is triggered. More than that, and you will likely be happier having multiple Squealer modules spaced around, connected to the nearest sensors.

Speaker Installation¶

The speaker attaches to connector J6 (SPK OUT) on the board. The plastic speaker enclosure can be mounted above or below the layout. For better sound fidelity, bore a 3/8" hole in the scenery or benchwork, and position the speaker enclosure with the opening on the side facing up. Camouflage the hole with scenery. However, this is user preference and may involve some experimentation.

Operation¶

After powering up, the blue LED will blink to indicate the Squealer is ready. If using the built-in sounds (ie: no microSD card), the blue LED will blink twice. If a microSD card is inserted with valid WAV files on it, then the blue LED will blink four times.

Sound is muted until the sensor detects motion. Once detected, the volume will fade up to the set level. Note that there are random silence spaces built into the program, so sound may not play immediately. However, the blue LED on the Squealer board will always indicate the current detection status.

Volume Control¶

The volume has 30 levels and comes preset at level 20. Level 0 is mute. There are ten levels above 20 to amplify custom audio tracks with low gain, but these levels should be used with caution as they may cause distortion.

To change volume, press the VOL UP or VOL DN button. The amber LED will blink briefly in response to pressing the button. When setting volume level 20, the amber LED will blink somewhat longer than normal to indicate it is the default level.

Custom Sounds¶

Custom sounds can be loaded into the Squealer using a microSD card. The microSD card must be formatted as FAT. The sounds must also meet the following requirements:

WAV file named with .wav extension (e.g. mp3 or other formats will not work)
Place .wav file(s) in the main directory of the microSD card (all other sub-directories and their contents are ignored)
16-bit, mono format
8, 16, 32, or 44.1kHz sample rate

The Squealer will load all valid files found on the microSD card and begin playing them in random order.

Specifications¶

Input Power: 5 to 24 volts DC
Size (Control Board): 3.75"(L) x 2.25"(W) x 0.5"(H)
Size (Speaker): 1.25"(L) x 1.25"(W) x 1"(H)
Size (Motion Sensor): 2.25"(L) x 0.25"(W) x 0.25"(H)

Open Source¶

Iowa Scaled Engineering is committed to creating open designs that users are free to build, modify, adapt, improve, and share with others.

The design of the Squealer hardware is open source hardware, and is made available under the terms of the Creative Commons Attribution-Share Alike v3.0 license. Design files can be found in the ckt-soundplay, snd-squeal, ckt-motion, ckt-irsense, and ckt-dingdong projects on GitHub.

The firmware for the Squealer is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or any later version. Firmware for the Squealer can be found in the snd-squeal and ckt-motion projects on GitHub.