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Beginner needs help modifying a mp3 player

Thread starter #1
Hello everyone,

I am working on a project and need some... well a lot of help with the electronic part of it.

I need to wire two buttons to opposite sides of a table that will trigger a mp3 player to play a track when pushed. I want to connect a speaker and some battery power source to the mp3 player. The buttons will trigger the same track, so i'm guessing I could just leave the mp3 player on that track.

I plan on using a Sandisk Sansa Express so I can use a usb extension cable to connect the mp3 player to a computer if I want to change the track.

I found this article and diagram of a mp3 doorbell. I want to do this minus the doorbell pretty much.

mp3 doorbell

I have no idea where to begin with this project. Any help with parts and how to do this would be greatly appreciated.



New Member
Ok, first of all, are you running the circuit off batteries or a wall wart?

Second, will you need to power the mp3 player or will it run off its own battery?

There are several elements of the project. They are:

1. Wiring a button to the MP3 player (doorbell button in picture)
2. Amplifying the MP3 player's output and sending to a speaker (speaker and amplifier circuit)
3. Powering the amp/speaker (Wall wart or battery, and possibly a voltage regulator)
4. Powering the MP3 player (3.5V regulator in picture, or use the MP3 player's own battery)

Step 1 is technically simple but will require a bit of delicate soldering. You'd have to locate the play/pause button, or the power on/off button on the MP3 player's circuit board and solder a set of wires across it to connect to the external button.

Step 2, you could use a LM386 audio amp IC, a couple capacitors and resistors and a small speaker. The picture shows what looks like an amplifier PCB from some radio or something. Or you could get one of those cheap MP3 player speakers, or even use a set of amplified PC speakers. If you build an amp, provide a 1/8" stereo plug to plug into the MP3 player.

Step 3, powering the amp, depends on the amp you're using. A LM386 can be run off a 9V battery or wall wart adapter.

Step 4, powering the MP3 player. The easiest way is to use the MP3 player's battery. If you want to power it from the same source as the amplifier, you'll most likely need to drop the voltage to whatever the MP3 player uses (probably 3-5 volts), using a voltage regulator. You could use a 78L05 if you need 5 volts, or a LM317 circuit adjusted to whatever voltage you need.
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Thread starter #3
kpatz thanks for the reply

To answer your questions I want both the circuit and mp3 player to run off of batteries.

It sounds to me like you understand what I want to do. Now I just need to know where I can get all the parts and how to connect everything.


Forum Supporter
Hi MikeCam,

Use an LM317 set to 3.5V as the regulator.

The audio amp on the picture seems like a TDA2822 amplifier wired as bridge configuration. Use regulator for powering both. Search here for circuits.

The transformer can be a 6V center tap type with diode rectifier.

I don't know much about that player. In some players the continuously pressing on the 'play' button will shutdown it.
Thread starter #5
Transistor495 because I'm new to all this I only partially understand what I need to here. Are you saying the LM317 regulator would power both the mp3 player and amp?

I think I would be able to understand a little better if I someone could make a list of the components I need to purchase and maybe where I could buy them.


New Member
Transistor495 because I'm new to all this I only partially understand what I need to here. Are you saying the LM317 regulator would power both the mp3 player and amp?
If both the amp and the mp3 player use the same voltage, you can run both from the LM317. But if the amp needs a higher voltage, you could either use a 2nd regulator set to the higher voltage, or power it directly off the battery/adapter. For example, if you build an amp using the LM386 IC, you can power it directly from a 9 volt battery, and use the LM317 (also connected to the battery) to get 3.5V to the MP3 player.

Or, just use the MP3 player's own battery and eliminate the LM317 circuit entirely. Either tap that battery for the amp or use a separate 9V battery.

I think I would be able to understand a little better if I someone could make a list of the components I need to purchase and maybe where I could buy them.
That depends on your location. In the USA, you could get most/all of the parts at a RadioShack store. Or online at digikey.com or mouser.com. In other countries, there may be a different local store/chain or online store you can get the parts from.
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Thread starter #8
I have changed my plans for this project a little to make it easier. I purchased speakers that run off of 2 AA batteries and just plug straight into the mp3 player. I also decided to stick with the battery on the mp3.

I took the mp3 player apart and quickly realized it was an updated version of the express. I need to connect TWO switches to the play button that will both trigger the same song to play. I have purchased some things and need to know if they will work.

I have purchased:
Hookup wire: 22-gauge solid wire. Rated 300V, 176°F(80°C)
Pushbutton Switch: SPST Momentary rated 3A at 125VAC 1.5A at 250VAC

Will I need anything else in order to make the switches play a song when pressed?

Momentary Switch

How do I connect the switchs to the controller? The play button is the top button in this picture.

I have no experience when it comes to this stuff, so any information will help.

When everything is connected the mp3 player will go in this case with the speakers on it. Hopefully this will protect everything under my table.

If anyone is wondering what this is for, well here is a pic.


Well-Known Member
Most Helpful Member
Don't those tiny little spearkers have no bass and sound horrible?

Or are you just listening to cars driving on a highway?
Thread starter #10
They work for what I am doing. Mp3 format is compressed and there is very little bass anyways. If you're not going to be helpful please don't respond.


Well-Known Member
Most Helpful Member
Some MP3 songs are compressed but most are not.
They have plenty of bass if your speakers are big enough (yours are not).

Somebody from India posted the kind of "music" played there. It had no bass.
Are you playing Indian music?

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