This is long overdue, delayed by so many other projects but I finally got around to the big monorail audio upgrade!  Please let me know if you find any inconsistencies in my instructions.

This is the first project of my transition from selling monorail upgrades to giving away the information on how to do the upgrades yourself.  I hope some adventurous modelers try it!

Want better (and more varied) audio for your monorail?  Here it is!

The new audio system is installed in the rear cab where there is plenty of space to install an audio board, larger speaker, and two batteries to power the system.  Audio tracks are triggered when the magnetic reed switch in the rear cab passes over a magnet installed underneath the beam.  The audio board can play up to 11 tracks* in sequence or random.      *FX Mini can only play up to 8 tracks


    This version uses the Adafruit Audio FX with a built-in amp or FX Mini and PAM8302 amplifier - they sound the same

    The system fits WDW models, DL Mark VII is almost ready but not 50th Anniversary.

    Requires some soldering of small wires

    Total cost is about $65 not including the tools which you may already have.  Tools may range from $10 to $30+ depending on quality.

1 - order the 3D printed mounting bracket from Shapeways (requires some drilling and tapping) $10 plus $xx shipping



add the 3D printed upper and lower speaker boxes to the Shapeways order - see #5 below

audio bracket


spkr box

2 - order the battery holder, power switch, and reed switch from DigiKey (also 28 AWG wire if needed)

        battery holder 2xAAA Keystone 1078 ($6.71)

        reed switch RI80SMDM-0510-G1 ($2.15) or RI80SMDM-0510-J1

        power switch CL-SB-23C-01 ($1.17 silver)

            * if you are ok with removing a battery to shut off the system you could get by without a power switch

3 - order the Audio FX 2 MB from Adafruit - $20 (the $25 16 MB version is if you plan for a lot of WAV files)


audio wired

4 - order the 3.3 V or 5V step-up regulator from Pololu  

        * the price of the 5V part went from $4 to $20 overnight, I have not tested a replacement yet.

        I have tried the 3.3 V part and it works ok but audio volume may be a bit lower


5 - order the speaker and enclosure

    SoundTraxx 20 x 40 mm #810103 - $14 at Streamlined Backshop

    speaker box upper - $9 @ Shapeways (WDW and Mark VII are different) - spkr_box_20x40x17_longi

    speaker box lower - $4 @ Shapeways (WDW and Mark VII are different) - spkr_box_brkt_20x40x20_longi

OR spkr_box_20x40x15_longi_2 - the difference is 2 front mounting holes and a lower box to make it easier to install a roof beacon later.

        -- requires drilling & tapping in the monorail shell - provides better sound


6 - order the magnet(s) from K&J Magnetics


        $1.26 each

7 - order tools and hardware from McMaster*: 2 mm x 0.4  tap ($17), 3 mm x 0.5 tap ($8), 1 mm or 0.040" or #60 drill

    2 mm x 6  nylon screws ($7/100), qty 4 and 3 mm x 5 screws ($5/100) qty 4 (NWSL may offer packs of 8 screws for about $1)

    *eBay or Amazon may have less expensive taps, the quality may not be great but they only have to cut plastic

Done ordering!

Cut the main hole in the bottom of the monorail rear cab

   cut a rectangular hole 18 mm wide x 50 mm long starting 20 mm from the rear surface of the shell. 

        the surface to measure from is the vertical surface under the coupler

   The 18 mm wide dimension is centered on the shell

   * cut around the bosses for the front side roller shafts to leave the bosses intact.

    The purpose of the hole is to install/remove the batteries, it doesn't have to be perfect since it will not normally be visible

audio bottom

 Use the bracket as a guide for drilling 2 mm pilot holes in the monorail

    (best to do this before tapping the bracket holes)

    enlarge the holes to 3 mm for mounting the bracket

    I used a countersink and flathead screws, nice but not necessary

audio brackets

Drill and tap two (2 mm) holes for the speaker box using the existing forward holes for the side rollers.

Drill 1.6 mm (1/16") from the bottom then tap 2 x 0.4 mm from the top to a depth of abour 6 mm.

Drill one 2 mm hole for the forward speaker box mount using the speaker box as a guide.

Tap the bracket circuit board mounting holes 2 mm, bracket mounting holes 3 mm

Clean out the holes for the power switch (1 mm drill), they are probably full of plastic powder

Drill holes for sound from the speaker in the bottom of the monorail (as desired, I use a 1/8" plastic cutting bit)

    my hole pattern is staggered rows on 5 mm centers (see photo)

Cut a rectangular hole to access the power switch actuator - 2.5 mm wide x 6 mm long (see photo)

Trim any ribs, etc that do not clear the added parts

wire the battery, power switch, step-up, Audio FX, speaker, and reed switch

    * the power switch is secured in the bracket by bending over some unused pins

    * the power switch is wired "in place" on the bracket

    * the power switch is a 3 position type to allow adding lights later

    battery + to power switch pin 7 - check the switch schematic, it is not straightforward

    power switch pin 8 to step-up IN

    battery - to step-up and Audio FX

    step-up + OUT to Audio FX

    Audio FX trigger 1 and ground to reed switch (polarity does not matter)

    Audio FX output (L channel) to speaker (polarity does not matter)

mount the reed switch to the bottom of the monorail shell (silicone)

install the speaker in the box (this is the older design with two front mounting tabs)

spkr box 1

spkr box 2

mount the speaker box to the monorail shell

audio spkr box

mount the Audio FX to the bracket with 2 mm screws

mount the bracket to the monorail with 3 mm screws

Follow instructions on Adafruit to load audio clips onto the Audio FX (must be WAV or OGG, not MP3)

        * Audacity is a good free audio editor that can export OGG files.

    *Here are the audio clip basics: Play Next Trigger - have up to 10 files play one after the other by naming them T00NEXT0.WAV (or OGG) thru T00NEXT9.OGG. Will start with #0 and each one on every trigger until it gets through all of them, then go back to #0

    *T00 means the files will be triggered by the "0" pin.  So "Please stand clear..." would probably be T00NEXT0.OGG to play first

    if an audio clip is longer than once around the layout it will continue to play after passing the magnet.

    the next clip will play the next time around

* The Audio FX with amplifier has a fixed output level, we can adjust the volume level of our audio clips to suit and that works well.  To get a board with adjustable output we can use the Audio FX Mini or Audio FX without amplifier and add the PAM8302 amplifier but this requires more wiring.


And where to get the audio clips?  Try: http://www.soundofmagic.com/sounds/tributes/JW/jacksounds.htm and YouTube.

To get you started here is "...por favor...". ;)

...and now that we have batteries and an unused position on the switch, how about some lights in the rear cab?   ;)  Later.