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If willing/able to go the DIY route, there have been OGR threads showing how to use low-cost MP3 players or MP3 sound modules.

mp3 player in s

I don't recall an S-gauge example off hand, but above shows one approach.  This particular MP3 player is a ~3cm cube.   As you can see, the speaker itself is not that large so I wouldn't call it room-filling sound. The tiny battery lasts maybe 1 hour or so before requiring recharging.  I've always taken out the guts to change the power source, speaker, on/off control method, etc. to meet a particular application.  This does require scrounging the web or "ripping" a Christmas CD to assemble your mix of MP3 music.  A $2 memory card holds hours or weeks of music so that's not an issue.

128mb microsd memory card

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Last edited by stan2004

Ray (and Stan) - have you considered getting a bluetooth speaker system?  that has the obvious advantage of simply using your iphone or computer as the source.  There are a couple of stereo BT systems on Amazon that look like they'd fit in a boxcar - or perhaps better yet, make them a flatcar or gondola load, which would make changing the batteries easier.  I guess you could get fancy and figure out a way to power it up from track power.

diy rolling stock mp3 player possibly fits S gauge boxcar

Using stuff I had lying around, here's a video of one approach.  Yes, there are i's to dot and t's to cross but with some DIY persistence I think it could be done for a modest out-of-pocket outlay of cash.

An AC-to-DC voltage converter takes AC voltage from the operating-car's power pickups and converts to DC - set to 3.8V.  I removed the tiny Lithium 3.8V rechargeable battery and wired the DC output of the converter to where the battery was attached.  I then attached a larger speaker than the stock tiny speaker (8 Ohm).  Technical note: the board has a type 8002B audio amplifier IC chip.  It is important to use a baffle (chamber) for the thin speakers that might fit in a S-gauge car; it doesn't have to be fancy as illustrated by the vitamin bottle neck.  The video doesn't show it well but messing with the baffle can have a dramatic difference in sound volume and bass.

I confirmed there are buckets of "free" downloadable Christmas songs in MP3 format on the web.  I placed a couple along with some other train related MP3 sounds to illustrate the concept.  The photo shows the directory of files on the microSD card; I think it's common knowledge (?) that a convenient way to transfer MP3 files to a microSD card is with an SD-adapter as shown in video.  Most, if not all, MP3 player modules simply cycle thru all the files on the memory card.  In the video I am pressing the "next song" button to move things along!  In this case you simply apply power and it just starts playing.

The crossing bell MP3 "song" was leftover from an OGR thread on a low-cost DIY crossing-bell sound accessory.  It reinforces the concept that an MP3 player, typically associated with playing music, could be re-purposed for non-musical layout sounds.

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  • diy rolling stock mp3 player possibly fits S gauge boxcar
Last edited by stan2004

Stan, Wow that looks like it might even fit into HO. Thanks for showing this, I am not an electronic wizard, your mention of the type 8002B amplifier IC chip, not sure what that would require in the build, maybe the ohm rating of the speaker?  I really do appreciate you doing this illustration for me and I am sure others will pick up on this.

I may come back to you with some questions on this.

Thanks

Ray

8002b chip

The 8002B is already on the board of the cube-player.  I made note of what's on the board as this would be one of the first questions a hard-core DIY'er might ask since the audio amplifier capability governs the choice/range of speaker Watts, speaker Ohms, etc.  A PDF datasheet is attached - I only include this as background.  For your application, you can ignore the techno-babble.  Just put in a larger 8 Ohm speaker that fits.

If you are seriously considering this, I will assist you in identifying suitable items.  I am an eBay addict and don't mind waiting weeks/months for "free shipping" from Asia to save a buck.  But if this is for Christmas 2020, I suppose you ought to consider domestic sources though prices are generally 2x-3x YMMV.  I've noticed that more and more of the eBay electronic stuff relevant to OGR projects can be purchased from Amazon that qualify for the $25 free shipping and/or Prime.

Also, it helps to know how this will be used.  That's what I mean by i's to dot, t's to cross.  For example, will the car ever run on a track with DCS?  If so, there's a 25-cent "DCS choke" that should be added.  Except you can never buy just one DCS choke without incurring huge minimum qty or shipping overhead.  How exactly do you want to turn it on/off...or maybe it always runs when on a powered track?  Do you really NEED (or just WANT) volume adjustment?  And so on.  This is all part and parcel of the DIY adventure! 

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Last edited by stan2004

Stan ,

I do plan to build this, I don't have DCS, but I would likely run it on both Legacy at 18v and if possible on conventional/ variable voltage. I would probably use a slide switch mounted on the chassis to disconnect power from the track and be able to operate silently if need be. I understand the EBAY addiction, I spend more time there than I should. I do appreciate any help you can give me for aquiring the proper materials.

Ray

DIY ebay mp3 player

The MP3 player itself and microSD memory card are widely available on eBay; they are duplicated on the right above.  I figure you might already have a microSD-to-SD card adapter to allow plugging the microSD card into most laptops to load your sound files. You didn't specify how anxious you are to get this going, but if coming from Asia your Christmas might be a Silent Night.

I found a guy in the US selling a pair of wired 8 Ohm 28mm speakers removed from equipment.  $3 each seems to going rate even on eBay Asia for 28-30mm speakers.  There are train sellers of "premium" HO or even S sized speakers but that's a different discussion.

The AC-to-DC converter is not the exact one I showed in video but is the same width (just under 30mm).  I was targeting 30mm as a "safe" maximum dimension to fit in an S boxcar.

This project does require soldering - to remove/replace the battery and the supplied speaker.  And you do need a voltmeter to set the output voltage of the AC-to-DC converter to 3.8V (to simulate the battery).  I assume you can come up with an on-off switch and splice it into the power supply path.  I figure you can cobble together some kind of speaker baffle/chamber using household items; I suppose you can open the boxcar doors to let the sound out...or drill holes in the chassis floor as many sound-cars do.

Yes, there always seems to be "one more thing."  But if you, or anyone else for that matter, are still interested in pursuing this, let the games begin!

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  • DIY ebay mp3 player

But wait, there's more!

diy ebay mp3 player with volume control

In the 2 birds with 1 stone category.  For just over $1 w/free shipping (from Asia) you can get an amplifier module with rotary volume control.  Obviously the volume control can double as an on-off switch in that turning to minimum volume effectively turns the music off.  The additional module is powered by the 3.8V from the AC-to-DC converter.

Also, I show the actual recommended AC-to-DC converter in the previous post.  It's very similar to the one in the video but always good to see proof of concept with the real McCoy!

In the fine-print department, the MP3 cube player has a +VOL and -VOL button.  It remembers the last set volume between use...but if you want to change the volume it can be inconvenient to access the silver mini "buttons".  Hence for the modest additional cost, real-estate, and just a few additional solder connections, I recommend the volume control module.  This also goes to the occasional OGR topics where someone wants to know how to turn down the volume on some particular layout accessory.

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Stan,

Thanks for the additional information ànd parts post.

Sorry for not acknowledging sooner, winter on its way and needed to be in the yard before I get buried with the white stuff. I am wanting to get this for this Christmas, once parts arrive l will be at this hot ànd heavy. I see out my patio door that here in Genesee it is getting white out there now.

Ray

Hi Stan,

The inside width of the car shell that I propose to use is 39mm, the interior length is182mm between the mounting posts and the interior height is 38mm. The chassis of the donor car is of sheet metal construction. The chassis is  from a Gilbert AF operating box car and the shell that I will use is from a Lionel Flyer Christmas car. The shell and chassis will fit with minimal mods to the chassis.  I am considering using a dc-dc buck converter and putting a 1000uf 35v cap between the rectifier and the buck converter to even out the power in the case there may be dirty track,  might that be a good idea or am I all wet?

You're definitely on the right track.

ac-dc vs dc-dc with loose parts

If you are comfortable working at the component-level (i.e., soldering, wiring, etc.) your options expands greatly!  That is, physically separating the bridge rectifier and large input capacitor provides more mounting options.   For example, there is a 1000uF capacitor on the AC-to-DC module which is the tallest component.  But options expand if you can mount it, say, sideways.

Your dimensions seem more than adequate but it's funny how when you actually start installing, wiring, and so on the space seems to vanish!

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Last edited by stan2004
@RickO posted:

There's an o Guage boxcar  Christmas music system"take out" on the FS forum now if it'll fit.

Maybe ask the seller for the dimensions.

RickO

Thanks for the heads up on the for sale forum. I am going to build a car up as Stan has shown. I am not sure all the parts will arrive by Christmas so I purchased one of the takeouts that were for sale, kind of a bonus I'll have two musical cars.

Ray

What did you decide to do about a speaker?  And do you plan drill or punch out the chassis to mount the speaker downward-facing on the chassis floor?

While you're waiting on components, I'd think this would be the perfect time to assemble your Christmas music MP3 files.  This would be a good time to resolve any issues with the MP3 side of things. 

I have the pair of speakers that you recommended on order, not sure yet, may mount to the ends of the car and drill a number of holes there or to the chassis, it depends on the fit. I can experiment with a junk body and temporary install to find how the end mount sound works out.

Yes when the player arrives I will attempt to start putting that together.

Will keep you posted on progress.

Ray

Ray, I have been following this thread and hope the project works out for you. I was slow responding until I began thinking about my own Christmas projects.

Lionel made an S gauge Christmas Reefer that plays Christmas music. It is part of set 6-49621 from the 2009 Vol. II catalog. I have attached some information about the set and the reefer. As far as I know none of these cars or the engine were offered for separate sale. A similar engine was cataloged, 6-48059, but that engine is numbered and painted differently. I have the set but have never opened it, it is MSOB. I did inspect an open set and saw all the contents. The other feature of this set is it includes a circle of 27”R curves with Lionel stamped on the ties rather than K-Line.





C21A7D43-47EF-4CE2-9BA6-3C8E27A9EBCAB6D2A515-FA7F-4204-AA32-8785482526F3F14134D0-D7BF-4305-B5F3-76D04F10D99E7AF24228-CD45-47DB-828B-AD917CDF76AA

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  • C21A7D43-47EF-4CE2-9BA6-3C8E27A9EBCA
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  • F14134D0-D7BF-4305-B5F3-76D04F10D99E
  • 7AF24228-CD45-47DB-828B-AD917CDF76AA

I see that Lionel car uses a 9V battery.  Track power vs. battery seems to be the first decision to be made for DIY sound boxcars.  I seem to recall OGR discussions where the cost of retro-fitted powered trucks if not starting from a so-equipped operating car well exceeds the cost of the sound generating electronics!

A typical alklaine 9V battery might be rated, say, 400 mA-Hrs.  Let's say the electronics draws 40 mA while operating.  40 mA x 9V = about 1/3rd of a Watt of power.  That's probably about right for some background Christmas music.  That would be 10 hours of operating time.  Seems reasonable.

If going the battery-route with these MP3 modules, note that the scavenged MP3 players were designed to operate on a rechargeable Lithium battery.  All the MP3 players I've seen have a USB charging port just like a cell/smartphone.  I recall though that cheap MP3 players typically have only a crude battery charging circuit...rather than the "smart" chargers that automatically know when to stop charging.  So if going the battery route, do your due diligence!

Last edited by stan2004

I have been away from the forum for a couple days, came back here and I see I have received some more information about these projects.

AmFlyer, Hey, thanks for posting the illustrations of the car with the instructions. I was wondering where Lionel had placed the speaker, I see it's over the truck. I was also wondering about the battery replacement, pulling the shell makes that simpler. This helps me to move along with the car for which I acquired a Lionel Christmas music system that came out of an O gauge car.

Stan

Yes on the car that is going to get the MP3 player that will use track power through a buck converter, I am planning on removing the battery and wiring from the buck to the MP3 player as you illustrated in one of your pics above. I am still waiting for some of those elements, thus the desire to do the battery powered car to be sure of having one musical Christmas car this year. Besides with the MP 3 car I can change the card and thus play railroad music the rest of the year.

This is a fun project, they both are and I want to thank everyone for their input.

Ray

Hi guys, Back again.

I received the MP3 player and the card, I have the music on the card and tried it in the player, all is good. I am now waiting for the amplifier, than will be complete. I have decided to put this system into the Polar express coach. The coach already has the power pick-up trucks and there is plenty of room for this setup. Hopefully the amplifier will arrive in time for Christmas. I will keep you posted on the progress.

Ray

Last edited by Rayin"S"

Back again, I received all the parts and put it together, using the amplifier I got a high pitched squeal from the speaker. I took the amp out of the circuit but made the mistake of not having a speaker hooked up when I applied power, I then got a dose of magic smoke from the MP3 player, all is quiet now while I wait for a replacement player.

Ray

Yikes.  Well, so much for having music by xmas.

But you should not have gotten a squeal, and there should be no ill effect if you do not hook up a speaker to an audio amp.  If you still have everything sitting out, can you take some close-up photos of the wiring?  I'm thinking I might be able to see something that I took for granted but I was not explicit about. Otherwise:

The definition of insanity is doing the same thing over and over again and expecting different results.

Well Stan, I did purchase the music take out from a Lionel car and that is in a Christmas box car and working fine.

As far as the MP3 player, now thinking after the fact, I wonder if the squeal might have been caused by picking up power from the track, though it went through the rectifier, the Caps, and the Buck converter. Should I maybe have had a cap on the output of the buck converter? I maybe should have tried a battery input through the track, to see if that may have eliminated the squeal, before trying other things. Looks like I have a lot of maybe's.

As far as the amp goes the directions on the adjustable amp, they recommend not powering it without a speaker hooked up because it could damage the board.

I am looking forward to see the replacement MP3 arrive, now I want to take this to a successful completion.

Still a "Merry Christmas to all", Christmas is much more than trains and gifts.

Ray

Last edited by Rayin"S"

Stan,  I had already started to disassemble the player when you had asked for pics, I will attempt to add and explain. The first pic shows the Buck converter with the power going to the left side to power the MP3, the red and blue on the right side are the wires that had powered the amplifier, the Buck was adjusted to put out 3.8v. The red and black on the right side of the MP3 went to the amp. I disconnected to try going to the speaker.

The long red and black in the second pic went to the speaker, the red and black directly above the cap was the power input to the amp from the Buck 3.8v., and the red and black farthest to the left was from the output of the MP3. Do you see anything that I might have messed up here?

Thanks for any help you might be able to offer.

Ray

IMG_20201225_151535511IMG_20201225_151505456

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  • IMG_20201225_151535511: The car chassis
  • IMG_20201225_151505456: The amplifier circuit

Well, I see how I should have been more explicit in how to connect the MP3 module to the amplifier module.

ray mp3

Only 1-wire connects the speaker output of the MP3 player to the audio input of the amplifier module.

The "why" has to do with grounding and a truly techno-geeky concept known as BTL (bridge-tied-load).  So all you need to do at the audio amp input is connect the "L" pad to one of the two speaker output pads on the MP3 player.  It doesn't matter which pad you choose, but to keep things consistent note that I used the pad closest to the corner of the board - the orange wire in my picture.

And, yes, connecting two wires indeed explains why the magic smoke was released.  You can ignore the elaboration but here's the technical mumbo-jumbo if you'd like to glaze your eyes.  Modern DC powered audio devices (smartphones, tablets, laptops, etc.) use so-called BTL audio amplifiers.  Neither of the 2 output wires to the speaker in a BTL amplifier are "ground".  Simply stated, the 2 wires are mirror images (one positive, one negative) and is essentially a method to "double" the audio output to a speaker.  The middle pad on the 3-wire input of the audio amp module is "ground". So what happened is you connected one of the BTL outputs directly to ground which amounts to a short-circuit to the poor audio amp on the MP3 module.

Again, I apologize for not explicitly warning you that only 1 wire should be connected to transmit audio from the MP3 player to the audio amp.

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Last edited by stan2004

    Well Stan, I am back. I received a couple of MP3 players, I put one on to the chassis, connected the power input and then hooked up the amplifier to power and one wire to the MP3 and two wires to the speaker. I may have gotten a bad amp, it made no sound at all, but not to worry. I took the amp out of the system and put one of the speakers that I had purchased in its place and got the music. I thought the volume was a little weak so I replaced that speaker with one of my Fatboy speakers, a spare I had from some of my ERR Railsounds installations . Plenty of volume now, I actually had to reduce the volume on the MP3. It is a little late for Christmas but it is now playing Christmas carols, I plan on building one more in a box car and loading it with railroad tunes.

Just wanted to give you an update and say thank you for the pointers on building this, I am a happy camper now.

Ray

Happy camper is good! 

I'm sure we could get to the bottom of the amplifier problem but why bother!

Since you seem to be adept at editing the "volume" of MP3 files, one simple idea which you may have already done is to make 2 (or more) versions of your Christmas sound track each with a different "volume".  Not as convenient as turning a knob to adjust volume but with a simple change of the microSD card you can have a, say, low-volume and a hi-volume version depending on what you need at that time.

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