Intro: Pringles Ghettoblaster
This instructable shows how to make a spectacular multinational boombox using two "Pringles" speakers, a MP3 module and a plywood wine box. It can play MP3 files from SD card or USB memory stick. It has FM radio receiver and audio line input. The device have embedded light effects and can be controlled by remote control. The design combines some steam-punk and some modern looking elements and could be associated with the "Fusion" design style.
Step 1: Pringles Speakers
Months ago there was an advertising campaign of "Pringles" in which there was possible, when buying two boxes of chips to receive a speaker, which could be put over an empty "Pringles" box, acting as resonator, and this speaker could be connected with MP3 player or some other sound device. This assembling was producing relatively nice and loud sound. I ordered two of these speakers. The main reason for that was the following: my daughter enjoys listening of music - mainly using her smartphone. Whatever the smartphone producers claim - the sound coming out of the smartphone speaker is terrible - its bandwidth is narrow and shifted at higher frequencies and a lot of deviations worse the tone,.I wanted to try what the sound quality of these speakers is. I tested it with the empty Pringles box. The sound quality was much, much better then the quality of the smartphone speaker. The truth is that the size really matters, the size of the speaker. I decided to make some stereo sound device based on both speakers (each of them is mono) and MP3 player. In such kind of designs the main challenge always remains the making of the box (housing) - especially for electronics specialists, which do not have their 3D printer, do not have experience with wood processing, or do not have all the needed for that purpose tools. First my ideas was to use PVC tubes and some cheap MP3 player (something like this ) - but I could not find a nice way to fix it over the PVC tubes....
Then...I have found another solution...
Step 2: The Case...
I remembered that years ago I received as a present a bottle of a luxury Bulgarian wine (Khan Krum - Traminer 2005) placed in a nice looking plywood box covered with leatherette, which I put somewhere in my wardrobe and I kept it for some special cases.
I decided to use this box as case for my Pringles ghettoblaster.
Step 3: The Electronics Core....
Having nice looking box, I decided to find corresponding MP3 player. I have found the one shown on the pictures for ~ 7 USD (with shipping costs included). As you see it has remote control and the cables are included. It can play MP3 files from SD card (micro SD with adapter) and USB memory stick. It has FM radio receiver, which can store a lot of stations. There are also inputs on the PCB for audio signal - the module can be used as amplifier. Audio power amplifier is also embedded in the module. What more can be desired for the price of 7 USD!!!. You can try to find this module in ebay, aliexperss or DX using the search string: "MP3 panel module SD card". The prices vary from 4 to 20 USD...Different modules exist - with different features and for different supply voltages. The most of them are for car use and are supplied with 12V. The module which I used is designed for 5V power supply. The Pringles speakers use 3 AAA type batteries, what is equal to 4.5V. I wanted to use one common power supply source for the all electronic devices. That is the reason why I chose 5V supply module. I have tested it with regulated power supply source and it have worked with reduced supply until 2.9V.
Step 4: Preparation Works...(part 1)
The first step of the design work was to prepare both Pringles speakers. The input cable was going through a hole on the speakers side wall, what was suitable solutions when the audio source is external (not placed in the same box). I had to rearrange the cable in the way, that it goes out through the bottom of the speaker and could be connected to internal source. You can follow this process on the pictures.
Step 5: Preparation Works...(part 2)
The Pringles speaker use 3.5mm stereo audio jacks. I did not want to cut the cables and to solder them and I decided to make an audio splitter in which the stereo signal coming form the MP3 module should be split in two mono signals going to each Pringles speaker. The attached PDF file can be used for the toner transfer method for making the splitter PCB. For the splitter I have used two audio sockets (search in ebay "Stereo PCB Mount Audio Jack Socket")
Step 6: Design Works...(part 1)
The most important step in each design is the projecting - it is impossible to make a nice product based on a bad project. To have a nice looking device I used a very simple technique - I have drawn the box in original size on white sheet and I have used colored paper shapes corresponding to the speakers and the MP3 module and moving them around I have found their positions, which placement I liked most. Using CD/DVD markers, I marked the positions of the holes corresponding to the internal sizes of the speakers and the MP3 module, which had to be cut.
For the cutting of the MP3 module hole I used "Dremel" like tool. After that I have shaped the hole using small file until the size of the hole was exactly so big as the sizes of the bottom side walls of the MP3 module panel.
For cutting the holes for the speakers i used hole saw mounted on a hand drill. After that I enlarged and shaped the hole using sandpaper fixed over a deodorant flask with scotch tape. I have created additional openings for the speakers screw leads using small round file.
Step 7: Design Works...(part 2)
I wanted to have an audio input for external signal source - the MP3 player had these inputs available. Unfortunately I was not able to find any 3.5 mm audio socket, which could be mounted on the 8 mm thick box wall.
I decided to use for that purpose a stereo audio adapter 3.5 mm - 1/4", which I had available.I did a hole in the box wall, I soldered 3 flexible wires to the 3 contact rings of the adapter. Over it, from the internal side I put a small plastic tube (color marker), which I filled wit epoxy resin to fix strongly. I have checked the functionality of the audio socket using a headphone and 1.5 V battery.
Step 8: Design Works...(part 3)
The next step was to fix the audio splitter inside the box. I used a small piece of wood and two screws. With the screws I fixed the small PCB to the wooden piece and after that I glued the whole assembling using hot glue.
Step 9: Design Works...(step 4)
After the listed works, I have mounted and fixed the speakers - at first gluing them with universal glue, and after that making the assembling stronger by the use of lot of hot glue. The next step was to make the all ground and power connections. The MP3 module was not mounted but its supply cable was soldered together with the others. As power supply source I intended to use 3 AA type batteries. For that purpose I fixed a 3 AA type battery holder on the top of the box cover by the use of hot glue. its negative cable (the black one) was also soldered to the common ground.
To fix and isolate the connections I used heat shrinking tube.
Step 10: Again Design Works ....
Now is time to connect the MP3 module. The schematic of the all electrical connections can be seen above.
There is tricky moment in the connection of the MP3 module with the speakers. In the spec of my MP3 module was written that the power audio amplifier is composite. This can be... but more important is that it is connected in bridged (differential) configuration. That means - the speaker is connected to the outputs of two audio amplifiers, which work with opposite phases of the output signal. In this way higher power is achieved comparing to the single ended implementation. If you want to reproduce my design without using of the Pringles speakers, but using only the embedded power amplifier and only speakers - this is not problem. But if you intend to use additional single ended input amplifiers - only one of both speaker outputs should be used - in other case you can ground the second audio amplifier output and damage the module. I have chosen to use the spk+ outputs, but may be the better solution could be to use the spk-. The FM antenna uses one of both lines - I do not know which. To solve the problem I soldered additional cable as radio antenna. The cables comming for the input audio socket were also soldered to the MP3 module board. I have fixed the MP3 module panel by the use of two screws.
Step 11: Finishing Works...
To finish the design I needed to put some kind of holder. I decided to use old style handle, which I bought from a local store. I drilled two holes for it on the cover of the box and I fixed it with the attached metal screws and some metal discs. The only missing part now was the power switch, which I have ordered at ebay and I was waiting to arrive.
Step 12: Ready for Play....
The fully assembled and functioning Pringles ghettoblaster - combining the visions of the past and the modern present.