Music in the apartment. Embedding



    Good day, Habr!

    After several of my last articles, comments flashed that my devices do not belong to DIY, are difficult to repeat, etc., so I would like to offer a small article to your attention, as I embedded the player and speakers in the apartment. Almost all of the available tools and almost no development.

    Once upon a time, at the apartment renovation stage, my wife asked to make speakers in the apartment so that children could turn on the music / fairy tales or listen to the news without turning up the volume moving their kitchens to the rooms. It was estimated several options for how this can be done. Probably the simplest one is to buy some kind of wireless audio system, but you still need to power the speakers, buy a column on a carbine (: etc., but decided to do it in a simple way ...
    As a result, four years ago, into the kitchen, the corridor and the rooms were estimated (embedded in a plasterboard) with two wires (unfortunately, there were no photos), then repairs were made and during the entire time until the last summer, stubs of wires about 10 cm stuck out of the walls. All this came in a box mounted into the wall in the bedroom. There came the cable 220V.


    Fig.1. Built-in box

    By the time the repair was completed (about 3 years ago), I had already thought of everything. I bought the cheapest tablet, on the back cover from the inside I installed spring needle contacts. The device was supposed to be mounted on neodymium magnets on the wall and through these contacts to charge and produce sound. Then I used Android on this tablet , something went wrong, I realized that it was very inconvenient to poke around on the Internet, search for music, or record its sd card, and in general the lack of radio strained me. Of course, you can put the application and listen to Internet radio, but this is all wrong.

    Somehow I came across modules that are embedded in cars with short interfaces. Here on board there is already everything you need: Bluetooth, USB, SD, FM and even input / output to the headset. Thought it was what I needed. I chose the largest block in size to close all the chaos on the wall.


    Fig.2. Audio module

    Even choosing the largest one, it did not overlap everything that was sticking out of the wall, so I had to cut a decorative bar.


    Fig.3. Decorative strip

    Well, and since I'm paranoid, I cut out a place for a switch that would cut off 220V.

    On the 3D printer were printed on the body, a kind of column to hide the speakers. One part is screwed to the wall, a wire comes out of it, a speaker is inserted and the whole thing is covered with a lid. I wanted to make the speakers as inconspicuous and flat as possible so that they would not catch the eye. The daughter, seeing them on the wall, asked: "Dad, why did you hang it on the wall of the salt shaker?" So there is an idea to remake them.


    Fig.4. Wall mounted "c" olonki

    The module does not have a built-in amplifier, only a linear output, so I had to find my prototyping boards with a divorced amplifier. I must say that the speakers are small and the power of the speakers is 3W, so it was originally laid out, since it was not planned to arrange a disco, but only background music. The amplifier took the PAM8406 - it turned out to be a pretty good option, and for him I had scarves made just for such cases.


    Fig.5. Amplifier PAM8406

    All speakers of each channel are connected in parallel. I know that this is wrong, but it did not affect the sound quality, I checked it with one speaker and 4 in parallel.

    The power supply of the module was 12V, 5V was made of it through the LDO, which I removed and powered everything from 5V through a small power supply unit 2A. There is an EN pin on my amplifier board, so after going into sleep mode (from the remote), the amplifier also turns off. An interesting joint was found in the module: on silk-screen printing, the line input and output are confused.


    Fig.6. Installed module

    The module is installed at the door on the side of the room above the light switch, approximately at eye level. The backlight turns off after a specified time.


    Fig.7. Installed module

    As we see from the development, only the amplifier, and even that could be taken ready, I just had the boards and chips in stock.

    In the end, I can say that it turned out mentally. Playing music does not interfere with conversations with friends and does not distract, you can listen to the news on your favorite radio station. Basically I listen to radio and music via Bluetooth from my phone.

    Thanks for attention!

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