Jan 02 2014 January 2, 2014 July 30, 2018 434Comments by michaelcastor

PiPad Build

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Two weeks before I had to leave for Maker Faire Bay Area 2013, I decided it was time I built an enclosure for the PiPad. I’d been helping a guy in the Shed Tech Support queue that needed some help with his Maker Faire project, and thought “You know, I want a Maker Faire project too.” Crazy – right? I had all the parts, so really the only thing holding me back until this point was a deadline. According to Parkinson’s Law “work expands so as to fill the time available for its completion” so at two weeks, I didn’t have much time for expansion. I started on some conceptual CAD work for the project before so I had a *slight* idea of what I was doing.

Design Goals:
I like simplistic, functional design. I don’t like extra crap that doesn’t do anything and I enjoy fun, hidden features. I also like for my projects to look as “sexy” as possible. I thought about hollowing out a book and putting it in there (like Penny’s book computer from Inspector Gadget) but decided to go with a stand-alone tablet form-factor. Since I wanted to let the PiPad keep me company on flights, the enclosure had to look as factory as possible, while remaining accessible and usable. The last thing I want is for it to freak out the TSA or the old lady sitting next to me.

Bill of Materials:

  • Frame Material – 1/2″ Baltic Birch Plywood (local lumber supply)
  • Backing Material – 1/16″ Carbon Fiber Sheet (I buy scraps from here and happened to get a flawless, large piece. Don’t count on that!)
  • Finish – Watco Dark Walnut Oil Finish – Amazon
  • Latch / closing – 14 – NdFeB Magnets – Amazon (These are *probably* overkill.)
  • Battery – Anker Astro3E 10,000mAh battery – Puts out 3A @ 5V! Gives me about 6hrs of battery life.
  • WiFi – I’m using this adapter from Monoprice, but this one from Amazon should work well too.
  • USB HUB – IOGear Micro Powered USB Hub (removed from casing)
  • Bluetooth – After experiencing issues with an AZIO bluetooth dongle, I switched to one like this and it worked great.
  • Keyboard – Adesso Bluetooth Mini Keyboard
  • Main brain – Raspberry Pi Model B (Ethernet and 1 USB port removed.) Edit – The Raspberry Pi Model B has been discontinued. The most recent version is the Raspberry Pi 3 Model B+ which is available here. You’ll need to retool the build for this board or try to find an old Model B if you’re trying to recreate it exactly.
  • Heat Sinks for Raspberry Pi  – Amazon (There’s no airflow in the case so I figured this was a good idea.
  • Misc USB ends – Male A (3), Micro (1), Female A (I hacked an extension I had laying around.)
  • Screen – 10″ Capacitive Touch Screen with LDVS Adapter from Chalk-Elec.com. I had a great experience with this company (they are based in Malaysia) but have heard mixed reviews from others.
  • Brightness adjustment – 10K Potentiometer (I had this lying around – it replaced the light sensor that came with the screen / LDVS adapter.)
  • GPIO – Ribbon cable and connectors (male and female) for GPIO.
  • Power switch – Waterproof Metal On/Off Button with White LED Ring – From Adafruit.
  • Screen / backing adhesive – Permanent double stick scrapbooking tape -Picked up locally from Hobby Lobby (if this ever fails I’ll get the 3M stuff they use on iPads)
  • Hinges – 1″ Brass hinges (Picked up locally from Hobby Lobby)
  • Extension for battery charging – Micro to Mini USB adapter – Amazon (to extend the charging port to outside the case.)
  • Amplification – Fiio E5 Headphone Amplifier (Now replaced by the Fiio E6) – The Pi doesn’t have an on-board amplifier. This miniscule amp works and sounds great and pumps out enough volume to hear on planes.)
  • Audio extension – 3.5mm Audio jack (like this) and hacked extension cable.
  • Probably one or two other things I’m forgetting.

Associated Files:

Everything I used in one .zip file. (Now available on GitHub!)

Construction:
The principle components of the enclosure are 1/2″ Baltic birch plywood and 1/16″ carbon fiber (for the back). I designed the cut files in Vectric’s incredible Aspire CAD/CAM package (though everything I did was in 2D) and used the image tracing feature to digitally recreate the components to ensure enough clearance. The components were placed on a scanner and loaded into the software so I could manipulate them for what I thought would be the best layout. Fortunately the folks at Chalk-Elec published a datasheet for the display with dimensions, although the corner radius wasn’t listed (it’s 10mm if you’re wondering.) I wanted to make the back the same size as the LCD panel, but the carbon fiber scrap I had was slightly too small so I had to re-size. I intended to machine the slots for the components using multi-sided machining but kept getting my layers confused. Because I was short on time and had limited material, I decided I’d hand cut the necessary slots (which ended up being easier than I thought.) I bought a new spiral downcut bit for a smooth finish and turned my CNC machine loose on the wood. After a bit of sanding and an inspection, I machined the carbon fiber with a 1/8″ carbide Dremel bit, sanded, and did a test fit. Everything lined up!

Next I laid out the electronics and marked out where I needed to cut access holes in the plywood frame. After everything was marked I cut though one layer of plywood with an Exacto knife, popped out the layer, and continued down until the slot was deep enough. Then I popped in the component, placed on the top, and checked to see if any more material needed removed. The SD card slot was another challenge. After measuring where the SD card would be and marking the area that needed removed, I taped a level onto my drill and drilled a series of holes using a 1/8″ bit. Then I used a coping saw to remove the rest. The results were a bit jagged so I cut a strip of sandpaper and worked it though the slot until smooth. Once I was satisfied with the holes, cut out the area for the hinges and mounted them into place. I’m not sure if was just me or a “thing” with hinges, but once installed the frame didn’t quite line up. Despite tweaking as much as I dared, it still wasn’t perfect. I ended up getting mad, mounting a belt sander in a vise and sanding the heck out of it until it lined up 100%. Once I was happy with it, I drilled in holes for the magnets. After I got the polarity right (yeah – I messed up a few times) I glued them in. Once dry, I removed the hinges and applied several coats of rub-on varnish.

When the varnish dried, I glued the carbon fiber backing in place, then installed all the components and ran / soldered the wiring. I put the whole thing together (nothing anchored in place yet) and turned it on. The power indicator blinked on and after a few tension-filled seconds, it booted! Everything including the touchscreen functioned as expected (which NEVER happens for me). I shut it down, finalized the layout, and started anchoring the components in place using either hot glue (I used this mainly for the wiring), permanent double sided tape, and foam tape. The display was affixed “Apple Style” using some crazy strong permanent tape around the inside edge. I clamped the battery and screen down and allowed the tape to cure over night to ensure a good bond.

The next day I realized I had a problem – the touchscreen wasn’t tracking my finger and a section of the screen was the wrong color. I quickly realized that I didn’t have enough clearance between the back of the Pi and the back of the screen. At this point I only had a few days before I left for Maker Faire, so I started freaking out a little. The Pi had to stay in it’s current location and was already as low as I could get it due to the SD card slot. I tried bending the metal around the USB port down but the issue persisted. So I got out my exacto knife and some pliers and pried the metal USB housing off completely. Then I took some cutters and completely removed the top USB port connections and plastic. That had to do it, right? Nope.. now the Ethernet jack was touching. While it didn’t distort the screen it was causing the touch to be erratic – so out came the soldering iron and away it went! Essentially I converted my Raspberry Pi Model B into a Model A with 512mb of RAM. But importantly, it worked and the PiPad was complete!

Conclusion:

IMG_1295

This image was taken while on my fight from Ohio to San Francisco (using a mouse because the touch-screen doesn’t work with RaspBMC.) The PiPad preformed flawlessly and didn’t raise an eyebrow going through security. On the plain though, a flight attendant kept walking by, looking closely at the homebuilt gadget I had on my tray table playing Talladega Nights. At one point I could feel her looking over my shoulder and was sure she was going to say something. She nudged me (I thought it was over at this point) and said “I love that movie – you’re coming up to the best part!” I’ve taken the PiPad on every flight I’ve been on since then and it’s never raised an eyebrow.

PiPad_Back

I’d e-mailed Eben Upton a few times for work, but didn’t have the chance to meet him at Maker Faire Bay Area. I did catch up with him at Maker Faire New York though. Eben is probably the most humble, down to earth person I’ve ever met – I really can’t say enough about him. After a long chat I showed him the PiPad. After several compliments and a few minutes of playing with it, Eben graciously signed the back at my request. His signature looks amazing on the carbon fiber!

Future Upgrades:

I’ve been considering adding a camera and IR sensor but am not quite sure if I want to bugger up the case. I do need to figure out how to get the touch screen working in Raspbmc – evidently it isn’t compiled with the nTrig driver.  I may someday build a version 2.0 if I get ambitious..maybe if the Pi gets an upgrade. We’ll see!

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