Intro: Pinebox Portable Computer Case 3
As part of a larger project (a portable Raspberry PI computer, this is a design for a wooden box to contain the computer.
It's split into three instructables (although building of the three parts was done in parallel).
Part 1 is the outer box, Part 2 is the inner wooden framework for mounting the Pi and screen, and Part 3 is the lower woodwork for mounting the keyboard, batteries and IO port expansion.
Step 1: Keyboard Supports
My intention was that the keyboard can easily be removed to give access to a circuit board inside. This board carries an extended 40 way Raspberry PI IO port, for connecting projects to the PI. The actual PI IO connector is up inside the lid of the computer, and very hard to access.
To do this, the keyboard is supported on two wooden end cheeks, and held down by magnets. The keyboard has a steel base, which makes this easier.
The side cheeks were positioned to keep the back end of the keyboard level with the case, and the front of the keyboard needs to slide under, and engage with, the dark wood "lip" on the case. It adds a little angle to the keyboard, as the original keyboard is very flat.
The side cheeks screw into the case, to allow them to be removed/replaced if a replacement keyboard (wider/narrower) is needed in future.
A spacer piece was cut to fill the space between the keyboard and the case, on each side.
The supermagnets were drilled and glued into the wooden cheeks, and then a small stabilising/right angle support piece added underneath, to screw it in with.
The top of each keyboard support was then profiled to match a panel which holds the speaker grilles, switches and LEDS.
Step 2: Join Sticks to Make Panel
A couple of small wooden stops were then added to support the rear panel, so that it lies flush with the case.
Two pine sticks were edge glued and then trimmed to size to make this panel, so that it closes the space behind the keyboard.
Step 3: Add Cutouts
In part 2, I placed a magnet in the lid to operate this reed switch. This will detect when the case lid is closed and power down parts of the computer (screen, keyboard, mouse, USB hub) while leaving the Raspberry Pi and camera running.
The reed switch is recessed partly into the wood, to retain its position. This slot was milled out with a Dremel, and just fits between the speaker grille and the proposed switch/LED PCB.
Next, cutouts were made for two grilles to allow sound out from the internal speakers. These slots are cut to a tight fit for the grilles.
The grilles were cut down from the original speaker grilles on these cheap plastic speakers. A pair of old scissors or tin snips will cut the thin metal grille, and then it needs an edge folding down, to remake the cut edge.
Once the grilles are a good push fit, a bead of PVA glue was run around to lock them in place, and smooth the transition from grille to wood.
Step 4: Rear Ports Pod
To extend the two spare USB ports on the hub, and the RJ45 net jack on the Raspberry Pi, I created a small pod to hold the extender cables/adaptors. This is made from pine wood offcuts from the project so far.
To hold the USB extenders in place, you could glue/hot glue them to the wood. I used some polymorph to retain them, by putting some coarse grooves into the woodwork on all four sides around them, and then packing hot polymorph under and around, before uniting the two halves of the pod and squeezing.
The polymorph grips into the grooves on the wood, and the features on the USB extender, and forms a solid mounting that cannot slip.
The USB extension is done using two short USB A plug-socket extenders, and the network is extended using an RJ-45 coupler (pictured) and a short white Cat-5 patch lead (not shown).
Three small "stops" were glued into the case to positively locate the pod at the back of the case. It's hard to see, but there is a gap between the pod and the rear of the case, to allow a panel to be placed there.
Step 5: Rear Ports Panel
The main case has a generic square opening for all ports, which we can now start to close off.
Note: this plastic panel is for physical support/strength only, and will be overlaid with a wood veneer later, for neatness.
A couple of sections of a CD jewel case were cut and joined (solvent welded with some polystyrene dissolved in cellulose thinners) to provide a clear plastic panel to aid with marking in of connector positions.
With the pod and panel in place, I marked out the extent of the connector openings, and then roughly cut clearances around them.
More cutting on this, and the wood veneer overlay, will be done when the power PCB is made and mounted. At the moment, it only reveals the USB and net jacks.
Step 6: Speaker Mounting
These are the small PC speakers used to provide audio output. To mount them, a hole was bored into a pine block with a forstener bit, to match the diameter of the speaker base.
These blocks were then glued into position in the corners of the case, with the speakers in place to get the correct spacing! The rim of the speakers touch the outer faces of the case.
Step 7: Cable Passthrough Notches
Cables pass through the hinge area, between the base and lid. There is one USB data lead (connecting the Raspberry Pi spare USB port to the the USB hub in the base), two USB power leads (separate 5V feeds for the HDMI Pi screen, and the Raspberry Pi), a network lead extender, and two ribbon cables: 40 way (Raspberry PI IO) and 26 way (other interconnections for my PCBs).
To do this, matching notches are cut in the keyboard-panel and screen-panel. These need to provide enough movement for the cables to slide in and out of the lid, otherwise the box will not close.
For the three USB cables, I cut some pieces of shiny HD-polystyrene sheet (from an ice cream container) to go over and under the cables to stop them sticking to the wood (due to friction). These pieces have a T-shape to retain them in the lid, and are long enough that they won't dis-engage when the lid is fully back.
You will also note thin notches taken out for the ribbon cables to pass through. These are just wide enough to pass the ribbon cables.
More cutting/drilling is needed on this panel when I have the PCB that holds switches and LEDs that will go in the middle.
Step 8: Panel Mounting/Keyboard Trap
To provide support and attachment for the keyboard fill-in panel, some wood blocks were added as shown.
The horizontal blocks provide support along the back edge (and also extra thickness for the hinges to screw into).
The vertical blocks were built up and out to allow a 6BA bolt to screw into a hex spacer sunk into and Araldited in a small wood block (much like for the lid, but smaller scale).
Step 9: Mounting Points
Mounting points and stops were added to retain the two battery boxes. These are placed right at the front for best counter-balancing of the weight in the lid! The battery boxes just fit in, under the keyboard support.
Mounting points were added, from scrap wood offcuts, for two DC-DC converters. One is to convert the battery down to 5V to run the computer and display, the other is to boost the external power input to 29v for the built in battery charger.
Step 10: Power Isolator
To isolate the battery from the computer (if it's not in use for a period of time), a kill-switch is mounted in the base.
This is recessed in a metal shroud underneath, so it can't be accidentally switched!
An approximately 10mm hole was drilled through the base. Another matching hole was put in a packing piece of wood, to hold the metal shroud/cover of the switch. The shroud should lie flush on the inside, and be slightly recessed outside.
The switch is mounted onto a small aluminium plate, which is then screwed into the wood block and case. Check that the switch cannot be accidentally toggled, otherwise -- lights out.
Step 11: Paint and Clear Coat
The keyboard end-cheeks and IO expansion pod, were painted to match the rest of the black parts, then clear coated.
Make sure to mask the USB sockets so they don't end up painted! The net-jack coupler can be removed during painting.
Step 12: Done!
The finished case!
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