Assembly
The hardware comprises:
(a) a Raspberry Pi Zero. At the time of writing there are three versions of the Pi0. The version with the header installed will not enable everything to fit together with a reasonably sized battery. The version without wifi will need an external wifi usb adapter (and suffers much poorer battery life as a result). Best to use the one with wifi and without headers. Cost around £9.
(b) wifi. The range of wifi is affected by the Pi0's placement (its antenna is really close to a large block of metal, the headstock, so this is understandable). Signal reliability is much improved if an external USB wifi adapter with an antenna is attached to the receiving device (i.e. your laptop or computer). There are many of these on the market I chose the one pictured below, which works well. Total cost around £4.
(c) an SD card containing a configured Arch Linux install and the Bell Boy software. It needs to be at least 4GB in size but it is difficult to get ones that small, so any size up to 64GB will be fine - make sure you get one from a seller that sells original cards from known good manufacturers - cost around £6.
(d) the PCB. I have the bare boards manufactured by OSH-Park and PCBWay. The Kicad files and gerbers are in the github repository so you can make these too if you like. This second version of the Bell-Boy is much smaller than the first and uses some really tiny surface mount components. Soldering the bare boards up is, therefore, quite difficult to do (I had to make my own reflow plate!). If you want to try making your own see the PCB Assembly page.
(e) a case. These are pretty widely available for a low price (£3 (ish) plus shipping) from a number of sellers on eBay and AliExpress.
(f) a LiPo rechargeable battery. The device has been designed to work with two sizes of battery 803040 (8mm thick, 30mm wide and 40mm long) and 703040 (7mm thick, 30mm wide and 40mm long). A 603048 battery just fits but is not recommended. Although these batteries are really common, they do have their dangers and they can cause a fire or explode if mistreated. If you are to assemble your own Bell-Boy you will have to satisfy yourself that you are competent to handle them. See here for some sage warnings. The most important thing is not to crush, bend or puncture them and to never use them if they are puffed. The Bell-Boy will deal with charging the battery (it has a charging circuit built in). The peak charge current is around 250mA so ensure that your battery can cope with that (most batteries above 250mAh capacity will). Battery cost around £6. Bear in mind that capacity overstatement is rife amongst many LiPo battery sellers. Just because something is marked 900mAh, don't expect that to be the case.
(g) some hardware. Four M2x10mm pan head screws, one 7mm LED spacer, two 30mm diameter "penny" washers and four 5mm PCB spacers.
(h) a magnet. This is intended to affix the Bell-Boy to the headstock. I used a 10mm height neodymium disc magnet with a 30mm diameter. The Bell-Boy case has two washers in its base used to attract the magnet. If your headstock is iron or steel, then the magnet can be attached to the headstock and the Bell-Boy just clipped on before a recording session. The magnet needs to have a rough material attached to stop it twisting on the headstock or on the Bell-Boy. I used some sticky floor tape (of the type used to make steps less slippy) but you could easily use sandpaper cut to size. If you want to use the device on a wooden headstock, the magnet is still needed but I would use the type with a countersunk hole and either screw the magnet onto the headstock or stick it on with hot melt glue. If you can't find a 10mm height magnet, two 5mm ones (widely available) stuck together are fine.
The rest of this page assumes that you have a Bell-Boy PCB with all the surface mount components soldered on and properly calibrated. If you don't have one of these, head over to the PCB Assembly page.
To allow the right level of space above the Bell-Boy PCB so that a battery can be fitted, we want the Bell-Boy PCB to be pretty much exactly 5mm from the Raspberry Pi board. This requires putting your own pin header on a headerless Pi0.
The best way to do this is to mount the header onto the Raspberry Pi, push the Bell-Boy PCB onto the Pi, use the spacers and screws to ensure that the boards are properly separated and aligned and then solder the header onto the Raspberry Pi. See pic (this is not the way that the boards will be permanently placed, it is just this way for the soldering of the header).
There is a fair amount of metal to heat up when soldering the pins (especially if you are lead-free or for the power pins). You might find it easier to unmount the Bell-Boy PCB once you have soldered a few connections (for stability).
Note that the header is 2x16 but that the Raspberry Pi fits 2x20 header. I needed the extra space to fit a push button. The eight unused spots are on the side of the Raspberry Pi furthest away from the SD card.
There is an alternative to soldering your own header on which I used for some of my prototypes (it is much faster but trickier). It involved purchasing the type of Pi0 with the header pre-installed and cutting the header down to fit the PCB with a rotary cutting tool (such as a Dremel). If you take this route you will need a 6mm LED spacer and four 6mm PCB spacers and four M2x12mm pan head screws (you may also need a washer as these screws are a little too long). You need to cut the pins down so that the header on the Bell-Boy PCB sits flush with the plastic part of the header on the Pi0. Cut the 8 pins furthest from the SD card (two rows of four pins) on the Pi0 header flush with the plastic. You must also ensure that the LiPo battery you choose is no more than 8mm in height.
The LED should be placed on the non-component side of the Bell-Boy PCB - the longest lead of the LED should go into the square hole. Before soldering, use a 7mm LED spacer to ensure that the LED is the correct height above the board. After soldering ensure that the soldered legs of the LED do not touch the micro USB port on the Pi.
The push button switch should be mounted on the non-component side of the Bell-Boy PCB. It only goes one way.
The final step is to solder the battery, this again is intended to be mounted on the non-component side of the PCB. Be really careful with these. I would only ever use one that has a protection circuit built in. When soldering it to the Bell-Boy PCB solder one wire at a time and keep the free wire insulated (eg a bit of tape at the end) until you are ready to solder it in. Affix the battery to the Bell-Boy PCB using foam double sided tape or another method you are comfortable is safe. If there is enough space above the battery and the case put a foam spacer in (but don't crush the battery).
When fitting the battery, ensure that the screw holes in the corner of the board are free.
The case needs to be prepared by:
(a) affixing two 30mm washers in the base of the case. These are what the magnet is attracted to. To be sure they will stay in, I use some casting resin; (b) making a 3mm hole for the LED to poke through the top of the case (I use the micro USB cut out on the top half of the case as a guide - the hole should be made from the inner section of the case such that your drill or reamer is positioned as close to the (now vertical) long side of the case as possible and horizontally positioned just off the centre of the USB cut out (towards the short side of the case); and (c) putting a sticker on top!
Mount the completed PCB onto the Raspberry Pi and there is one more soldering task to complete. The Pi's RUN pin needs to be connected to the Bell-Boy PCB. The RUN pin is the square pad hole closest to pin 39 of the Pi0's header. The best way to make the connection this is to run a wire from the bottom of the Raspberry Pi using a stiff wire (I use a component off-cut) through the J1 hole on the Bell-Boy's PCB. I then solder the wire on the Pi0 end (don't solder the Bell-Boy PCB end just yet).
Put the spacers between the two boards and the screws from the top of the Bell-Boy PCB. Screw the stack into the case bottom (do not overtighten). Now all spacing is correct you can solder the J1 wire that you just soldered in at the Pi0 end. The last thing to do is to click on the case top (ensuring the LED pops through the hole in the top of the case as you are so doing.)
This is what it should look like:
Put the SD card (after programming - see below) into the Pi and push and hold the power button down for around two seconds until the LED lights red, then release the button. The device is now on. If everything is working, the LED should do a regular slow red flash for about 5-6 seconds before starting a slow green flash. The green flashing indicates that the Pi is booting and is getting the Bell-Boy software ready.
After about 30 seconds, the green flash should become intermittent. This means that the Pi has successfully booted and its wifi network is up.
To switch it off, you can do so by either using the web console or by pushing the power button for about two seconds until red flashing starts. The Pi will then take a few minutes to shut down (shutdown is indicated by a sequence of rapid red flashes).
After doing this you might like to go to the First Use page.
This section just covers the basics of the Bell-Boy software installation. The code is open source and can be freely downloaded but the icons used by the browser interface, whilst free to be included in a website or a product, are licensed from a professional designer so can not be supplied directly. There is a password protected file on this github that contains the images and I can let anyone who wants to use the software have the password. I can happily supply pre-programmed SD cards (with the icons and the sticker for the case) if you wish.
The software that runs the Bell-Boy is installed in a Linux environment - one particular Linux distribution called Arch Linux is used.
The first step is to install Arch Linux onto the SD card. Follow the instructions here (click on the "Installation" tab)
Once that is complete then the next stage of configuration happens on the Pi itself. You will need to have access to the command line of the Pi and the best way to do that is to use a USB ethernet connector and to connect to it over SSH. The PCB is designed so that you can attach the USB ethernet device to the Pi even after the PCB has been assembled. The initial username:password combination is alarm:alarm. Then enter the following commands
su root (type "root" as the password)
cd ~
wget https://github.com/BBUK/Bell-Boy/raw/master/setupBB.sh
chmod a+x setupBB.sh
./setupBB.sh
You will see lots of text going up the screen whilst everything is being installed and configured. The last step will be to install the icons and you will be asked to provide the password. If you don't have the password just press enter (no icons will be installed). The Pi will then automatically shut down if everything is OK.
Note that the calibration it actually stored in a chip on the Bell-Boy PCB, so you won't lose the calibration if you replace the SD card.
Be careful with neodymium magnets, they are very strong and can snap together suddenly pinching skin or anything left between them. They are also quite brittle so when snapping together they can break with pieces flying everywhere.
Licensed under the TAPR Open Hardware License (www.tapr.org/OHL)