Intro: Pinebox Portable Computer Case 2
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: Join Sticks Into Boards
For this part, I didn't use a cutting-guide layout. I used the back plate of the HDMIPi screen module as an assembly template/guide, to save any damage to the main HDMIPi screen. The maximum extent of the visible screen was marked across onto the protective film, which was still on the plastic.
This part will be painted, so it's less necessary to match the wood grain between the pieces.
A width of three pine sticks was needed either side of the screen. Two sticks below, and one stick above. Like in part 1, the sticks were glued up and clamped on a greaseproof paper backing.
Step 2: Bevel Into Frame
Before assembling the frame, each piece was bevelled on the inner edges to provide a smooth transition from the screen to the woodwork.
The critical dimensions here are that the inside of the frame is square, and matches the visible area of the LCD when mounted in its correct place. The outer frame will be trimmed square later to match the box lid.
As shown in the pictures, the top, bottom and side pieces are bevelled on one edge using a table saw jig to form the inner edge of the frame.
Then, the side pieces are cut to length while being bevelled again the opposite way up, on both short ends. All these angles are 45 degrees.
The two side pieces must be 125mm on the (short) face that is flat to the screen, to correctly space the top and bottom pieces apart. The side to side distance and position is adjustable by sliding the side pieces left and right. Ensure that the whole active screen area will be visible.
The four pieces are then glued into a square/flat frame and left to dry. It is not full strength yet, so handle with care!
Step 3: HDMIPi Mounts
The HDMIPi screen has six bolt heads that stand out from the surface, so a small amount of wood is milled away to let the display sit closer to the frame. These can be marked from the template (back plate).
By splitting a couple of pine stick offcuts lengthwise, a retaining frame was glued around the plastic template to keep the screen in place. It also helps strengthen the frame, by overlapping the frame joins in a different way, and provides something thicker to screw into later.
A gap was left along the camera spinner side, as the spacing is too close to allow a full length strip here (it will interfere when the screen meets the camera!)
Using some No 8 x 3/4" wood screws, spacers, and some speaker retaining clips, three clips were constructed that hold the HDMI Pi screen down into this retaining frame. The speaker clips bite down onto self adhesive pads to stop damage to the plastic of the display.
Step 4: Trim to Size
Using the case lid, built in part 1, measure and trim the screen panel to fit closely to the lid. Left to right alignment is important here, to leave enough space on the camera side. There is only about 2mm of clearance between the HDMI Pi module and the camera when set correctly!
Step 5: Cut Window and Camera Mount, Logo
Temporarily mounting the screen panel into the box lid, the position of the camera window can be marked in. This is cut out with an x-acto blade/chisel edge, and then a rebate for the glass milled into the back of the frame.
There also needs to be a shaped hole cut out to take the thumbwheel and shaft of the camera spinner.
Also I cut a 2mm deep square rebate for the logo on the left side, using the logo as a template to mark round, an X-Acto knife to cut the straight edges, and then dremel drill to mill away the material in the middle.
Step 6: Case Closed Magnet
For this computer, when the case is closed, power saving will be applied to cut the power to the display (can't see it), the keyboard (can't access it), the mouse receiver (what use is the mouse without the screen?) and USB hub.
To sense this, a reed switch in the base, and a magnet in the lid are used.
A 10mm forstener bit was used to put a neat, flat bottomed hole into the frame as shown, which will line up with a reed switch in part 3. The magnet is then glued in.
Step 7: Camera Mount Stops
To retain the camera in its correct position, some small "stops" are glued to the case around it, as shown, using the spinner module as the spacer.
Check that the view ports on the camera spinner align with the holes in the woodwork (and the front frame!).
A foam pad was stuck to the front of the spinner, just below the thumbwheel, to cushion the front frame pressing against it, when it's closed.
Step 8: Screen Panel Mounts/Stops
The screen panel pivots in/out of the lid, to allow access to the SD card (operating system) for OS backup purposes.
Three stop-blocks are positioned to support the bottom of the screen panel. Additionally, they provide more bite for the hinge screws. This puts the screen slightly recessed into the lid, at the bottom. The gaps between the blocks are left for passing flat ribbon cables between the lid and the base.
Next, the angle of the screen is set with some thin stop-strips across the top of the lid. The screen angles back slightly, until it rests tightly against the camera module, so it is set deeper at the lid. A square pine block in each corner is used to provide the means to bolt the screen into place at the top.
I used 2BA bolts and hex spacers as retainers here. The hex spacers were sunk into the wooden blocks and Araldited into place. Note: Block up the threaded hole at the bottom end, so it doesn't fill with epoxy.
I also ground some notches into the side of the spacers for better keying for the epoxy, to make sure they don't pull out.
Next I added an angled "stop" along the non-camera side, which joins the bottom and top of the screen at the correct angle. This will support the edge of the screen frame. On the camera side, two shorter strips are mounted, with a gap left around the area of the camera.
Lastly, three small angled pieces of wood are used to retain the bottom of the screen. The screen slides into the gap between this and the three stop blocks, then pivots in and bolts in place. These are trimmed from offcuts of pine, and are like tiny quadrant strips, and they sit flush to the edge of the case.
Step 9: Cable Clearances
Notches need to be put into the bottom edge of the screen frame to pass cables from the lid to the base. More on this in part 3 as the slots need to align between the two halves.
Step 10: Camera Detent Mechanism
This is needed for the camera spinner , see the final steps, to provide a positive "click" stop when turning the camera direction.
A plastic rounded pin (a small LED!) on a spring engages into a detented gear in the spinner that stops it every 90 degrees.
The spring is retained in a paxolin tube, and a wooden spacer (more scrap pine) holds it all in the correct position to align with the camera module.
You can just see the slot in the spinner lid that it will poke through.
Step 11: Finishing Touches
The LED flash for the rear facing camera needs a diffuser to help spread and soften the light from the high-brightness white LEDs. This was cut from a plastic diffuser head for an SLR camera flash.
Using the Eagle PCB printout as a template, two 6mm holes were drilled through for the LEDs to engage into, and then a rebate was cut out to take the diffuser.
A second diffuser for the front facing flash is installed in the outer lid. Instead of six holes, I cut a square hole to clear all six LEDs at once.
For audio recording, an omni-directional electret mic is mounted to the screen frame -- an undersized hole in the frame allows the sound in, and a snug fitting hole in a small block of wood retains the mic inside. This will connect to a USB sound device connected to the Raspberry Pi.
To assist with mounting small PCBs in place, some small blocks of wood were glued for the rear flash (2 LED), LIRC module (IR Tx/Rx), and front flash (6 LED). This will give thicker wood to put small screws into.
Lastly, some strips of self-adhesive felt were put around the edge of the screen, to provide a seal/protective padding for the HDMI screen when fitted.
Step 12: Painting/Logo/Clear Coat
Three small wooden veneer trims were added around the camera spinner/diffuser to hide the metal shaft of the thumbwheel.
All of the woodwork for the inner parts was primed with wood primer, undercoated, and then sprayed black. Mask out the flash diffuser and logo area, to keep paint out.
The "PInebox" logo was then glued into place, and the whole thing sprayed with clear-coat to protect it.
Step 13: Adding Glassware
The flash diffuser for the front flash was glued into place at this point.
All of the glassware around the camera and LIRC module was held in place with white silicone sealant. This not only holds the glass in, but seals it from dust/water ingress.
Once the sealant has set, carefully cut away any rubbery excess bits visible in the window with a sharp knife, and then clean the glass on both sides with isopropyl alcohol and a clean cloth/kitchen towel to remove any smears. It's important to get it completely clean, so it doesn't cloud the camera image.
For the LIRC module, a piece of IR-pass plastic was added inside the glass, and dotted in place with PVA glue. It allows IR light in and out, but prevents visible light (so you can't see the PCB/parts through the window). This is optional.
Step 14: Done!
The finished screen panel, ready to fit into the lid.
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