Kids Jukebox - Self build tutorial using Raspberry Pi

Introduction:

A jukebox is probably more outdated than anything playing music that we know today. But none the less, it delivered the most classy experience of listening.

The idea of building a jukebox for kids came during christmas unpacking several CDs which might be another means of listening to music endangered of extinction. Yet, CDs deliver a nice haptic sense of control that especially kids love in an age where they cannot read and thus are not yet capable of dealing with graphical iPod displays.

Thus, I wanted to build a haptic touchpad for controlling which music to play using a Raspberri Pi and the bluetooth speaker I have at hand. It is the perfect extension of the tigerbox (amazon) if you do not buy into the cards feature where you need to pay for content again.

The conrete idea of building materials came from random sightings within the house, starting with a magnet in my pocket and cotton pads on the changing table.

Here is how the result currently looks:

If you manage to build a nicer version, I would be thrilled to receive your photos!

Prerequisites:

Besides a Raspberry Pi and a random bluetooth speaker, you need the following material:

• aluminium foil (I used what I found in the kitchen and cut it in 1.5cm wide lanes)
• thumbtacks (I only found ones with plastic cover that I removed with a pair of pliers)
• cotton pads or any other material that is soft, may be compressed and creates a force against the pressure
• pin board made from cork (> 40cm x 30cm)
• sheet protector to allow chaning the song album selection easily
• 1-2 strong magnets as from photo ropes i.e from Amazon

I used a raspberry pi 4b 1GB for less than 40 USD. Other versions with bluetooth support should do fine as well. Minor adaptions of the code might be needed. Please let me know if you have problems in geting it to work.

• Raspberry 4b i.e 2GB from Reichelt
• Normal USB-C Power supply i.e from Reichelt
• 2x cable with crocodile clips i.e from Reichelt
• 10x 2kOhm resistor from Reichelt

Hardware Setup:

The aluminium foil works as a conductor just like a cable. You can pin stripes of it on the board using the thumbtacks. I suggest putting the 4 long stripes down first with 6 thumbtacks on each stripe with a 2cm by 2cm cotton pad piece underneath. Press the thumbtacks firmly such that the cotton pad gets higher at the corners. The 4 times 6 = 24 thumbtacks with cotton pads underneath should cover the area that you like to use as touch pad (I used A4 format). Then add the 6 shorter stripes on top with a thumbtack above and below the touch pad area. They must be placed with high strain, so their surface does not touch the 24 thumbtacks of the touch pad.

Here is a detailed view of the cotton pads in action:

After adding the sheet protector and the magnet on a random thumbtack it looks like this:

Finally, you need to connect the 4 long stripes and the 6 short stripes to the GPIO section of the Raspberry Pi. Please bear in mind that the Raspberry GPIO pins have no protection against short circuits. It may easily fry the device. That is why I put a 2kOhm resistor to each stripe of the touchpad with another thumbtack and connected the crocodile clips coming from the GPIO pins only to the other side of the resistors.

In my setup I used the GPIO pins 23, 22, 27 and 17 for the 4 long stripes from top to bottom and the pins 16, 26, 13, 12, 6, 5 for the 6 short stripes from left to right.

Software prerequisites:

I setup my raspberry by copying Raspbian Buster full on the micro SD card of the raspberry pi. Then I added an empty file called ssh to the boot folder in order to activate the ssh server and configured the wifi-connection of the raspberry by placing another file called wpa_supplicant.conf on the card according to this instruction.

Please make sure you installed python3 and you have it on the path. This should be the case for raspbian buster full.

Software Installation:

The code in this repo is just a quick-hack prototype of the idea. However, it works too well to do it right. If you like to build other things with the touchpad, please let me know. I am willing to implement a nice gpiozero wrapper in case someone actually uses it.

Configuration:

• You need to put the mac address of the bluetooth speaker you like to connect in two locations. There are .example files in the repo that you can copy and modify.
  • kids_jukebox/connect
  • pulseaudio/autoConnect.sh
• Please make sure you used the exact same GPIO pins as hard-coded in the source code:
  • kids_jukebox/kids_jukebox.py
  • mytouchpad/mytouchpad.py
• Copy or link 23 directories with sound files that can be played by vlc to kids_jukebox/playlist/current/0 up to kids_jukebox/playlist/current/22. Each directory is an album.
  • Number 23 does not exist since the field bottom right is reserved to shutdown the jukebox
  • Please look at kids_jukebox/playlist/readme.txt if you like to support multiple sets of albums. They can be changed on startup using two magnets.

The code can be installed on your pi using:

• rsync -av buttons kids_jukebox mytouchpad pulseaudio pi@pi: Where the pi at the end is the host name of the raspberry pi.

Log into your raspberry with ssh and run as user pi:

cd ~/pulseaudio; ./setup_pulseaudio.sh; cd -;
cd ~/kids_jukebox; ./setup.sh; cd -;
cd ~/buttons; ./setup.sh; cd -;

Restart your raspberry to see whether it works reliably.

You can use this template to put your album cover pictures and/or album names on the touchpad. The orange circles are meant for the case with multiple sets of albums where you can change the set with two magnets on the orange circled fields.

I hope you and your kids enjoy the jukebox and the touchpad! Please let me know if you have trouble following these instructions. Feel free to add issues or pull requests to this repo.

Problem solving:

Whenever you change the magnet, kids_jukebox will try to reconnect to the bluetooth speaker. This solves quite some connectivity problems. It would be possible to monitor the status of pulseaudio and try to reconnect as long as no speaker is connected. But again, this is just a quick-hack prototype that happens to work pretty well for me.

If you just want to test your touchpad, you can disable the kids_jukebox service using systemctl --user stop kids_jukebox and run mytouchpad/mytouchpad.py. It will display the touch pad points that it detects as pressed and it will show in brackets how often it detected those when trying to detect 5 times. The touch pad points are numbered 0 to 23 from top left to bottom right. The kids_jukebox only reacts to changes of the magnet if it finds 5 consecutive measurements pointing to only a single magnet on one field of the touchpad.

Please, bear in mind that the kids_jukebox service will shutdown the raspberry pi when placing the magnet on field 23 (bottom right).