Mustard Tin Music Players

There's a meme in the world of hobbyist electronics about building projects into an Altoids tin.  Someone has even put an electronics lab into one.  I've chosen to do something a bit different - a Colman's mustard tin.  Two different ones, in fact, a 4 Oz one and a 2 Oz version.  Same sort of project though:  a slimmed-down version of the PiFi network music player which you can read about the evolution of in earlier posts here.

The 4 Oz version

Having upgraded my PiFi to use a Raspberry Pi 3 and a different DAC, I was left with a seemingly redundant HiFi Berry DAC that would only work with an original Pi model B (because of the GPIO pin layout, which changed with the B+).  I noticed that the combination of Pi model B and DAC would just fit into a 4 Oz mustard tin, and so a scheme was born to make a more portable version of the PiFi which could be used, say, at a barbecue, powered by a car battery or other 12V source.  It would use a USB flash drive to store the music files as mp3 rather than FLAC and be controllable only via WiFi through a USB adapter (so that's both USB ports used).  Software setup is essentially the same as for the original PiFi, i.e. it boots from the SD card which contains the root file system and mounts the USB flash drive at start-up.   USB flash drive is formatted as NTFS to make it easier to load music onto it.  There's still a samba server running so you can do file management over WiFi, but plugging the USB drive into a PC is much easier & quicker.  Logitech Media Server handles the user interface and Squeezelite handles the playing of music. To make it fit into the tin, I did have to cheat a bit with the SD card.  Pi 1 uses a full-size card which sticks out too far at the bottom, so I've used a micro SD card and a small format adapter, which doesn't stick out at all. You can see it in the photo above.  Also visible above is the DC-DC  converter to drop the 12V input down to 5V - it's inside the black heat-shrink just inside the open end of the tin.

I happened to have some yellow PLA, so I printed a new lid for the mustard tin to accommodate the USB ports, a shutdown button and a 3-colour LED.  The LED flashes green once the player is booted up and running and turns red  whilst it is shutting down.  There's another printed part in the bottom of the tin to steady the bottom end of the Pi, so it won't accidentally come into contact with the metal walls of the tin.  There's a power socket on one side and a 3.5mm jack on the other.

It's worked well so far, the only glitch is that you can't run it and an amplifier from the same battery, at least not the battery powered amplifier I built to play music in my garage.

The 2 Oz tin

You can't get 4Oz tins of Colman's mustard powder in any of the shops around here anymore, but you can get 2Oz tins, so I also happened to have an empty one of those.  I also happened to notice that Pimoroni were selling a little DAC board using the same chip as the old HiFi Berry, which was exactly the same size as a Raspberry Pi Zero.... and they'd both fit together inside the smaller tin with space to spare for another board with the circuit I used in the PiFi to switch power on & off plus a DC-DC converter.  Pimoroni call their little DAC board a PHAT DAC, PHAT being an acronym for Pi Hardware Attached (on) Top, because it's meant to plug straight onto the GPIO header pins on top of a Pi.  They supply it with a header block, but it's not soldered to the board.  I like this, because a Pi zero also comes without header pins attached, so I was able to save a bit more space by putting the header block on top of the DAC board and putting some right-angled pins on the Pi Zero so they stick out beneath far enough to still make contact with the header block and still allow connection to the top of the Pi.  I suppose this makes it Pi Hardware Attached Beneath - a PHAB DAC.  I also like that.

If I were to do this again, though, I'd modify a set of header pins so that only those I need to connect to for LEDs & shutdown signals would have the right-angled pins, the others would just be straight through to the DAC beneath, and longer.

When I did this, the Pi Zero W was not yet available, plus I'm not sure how well it would work inside a steel tin, so I have a very small WiFi adapter in the lid, connected via a very short USB lead with a type A socket at the adapter end.  At the Pi end, the wires are soldered directly to a micro USB 'shim' like this one.

Here are the reassembled parts ready to go back in the tin.  You may have noticed in the picture above that the inside of the tin is lined with transparent plastic to insulate it from contact with header pins, circuit boards etc.  In fact it's double-insulated by the bit of old milk carton that you can see here.

Like the PiFi, this one has two buttons, a white one to start up and a red one to shut down.  There are also separate red & green LEDs which work the same way as the red & green in the 4 Oz version.