So I’ve made a smartwatch previously and while they’re cool and all, they had nothing on the hype created when Google Glass first came out. For reference, Ochi is eye in Romanian – there is no language preference, I just thought Ochi was a pretty cool related word.
While I’ve wanted a pair of Google Glass for a while, I had no reason to apply for the beta period, never mind the ~£1200 required to purchase them. I’d dreamt of an eye based display for months, evaluating a few options such as this FPV eye module that I bought. The eye module seemed promising until I realised the efforts involved with driving a composite signal without an FPGA or dedicated signal generator chip (which further required a VGA input…) which kind of put this module out of my realm – unless I fancied super miniature electronics and BGAs left right and centre!
The whole idea of smart glasses went out of my head for a while after then – I fortunately don’t even need to wear glasses yet! My next step came when I was searching banggood for what ever was on offer with no intention of buying. I came across Google Cardboard – Google’s attempt at a VR headset design based on your mobile phone. I decided to browse eBay for it and found a cheap source, the cardboard cutout and two biconvex lenses for £2.99!
Initially, I wanted to try the Google VR app but unfortunately, my phone didn’t have enough space rendering it somewhat useless. Instead of giving in, I had a look to see how good the lenses were at viewing close up objects, as they are meant to with your phone screen. Testing the lenses and a 1.8″ LCD screen showed promising results with the issue being that the LCD was just a bit too large, meaning the whole screen couldn’t be fit into the focus range of the lens (aberration at the edges, predominately along with lack of focus). The task was then to find an LCD suitable for full viewing by these lenses.
I had a 1.44″ LCD to hand from previous projects so I decided to test this too. Unfortunately, it had the same problem as the 1.8″ LCD which was even more frustrating! It was just a touch too large to be completely in focus. Annoyed at my lack of materials, I decided to scour the net for any small colour LCDs and I came across a tasty 96×64 0.95″ OLED screen at buydisplay. This screen was perfect! It could be interfaced through SPI and was small enough to very likely fit into focus since the 1.44″ LCD was so close. Then came the issue of a PCB. I’ve done a fair bit of PCB design but designing something to be this small and compact, along with allowing for mounting methods was quite a challenge. I decided upon a platform based on the STM32F051K8 LQFP32 microcontroller and this LCD. One of the issues with such a small LCD is the lack of boost converter meaning I needed a dedicated boost converter circuit too but that wasn’t a major issue.
So the glasses had at least some form of usefulness, other than telling the time, I’ve added a HM11 bluetooth module. I’ve not used the HMxx series of bluetooth module but I have used a couple of the HCxx series so I’m hoping their the same. The HMxx series offers low power and the new BLE protocol and with the latest Android updates, I’m hoping to write a small app that merely pushes notifications through the bluetooth serial port profile to the glasses though this may prove harder than it seems!
Layout of the first Ochi board
As can be seen, it lacks quite a few features – mainly a USB micro port and battery charging method. The power is supplied through wirepads and the battery will need to be removed for charging. This is however a perfect prototype for testing the OLED and HM11 modules. The two through holes on the top left are going to be used for mounting and the two wirepads at the bottom will be used for connecting two touch sensors which will sit on the glasses frame.
Obviously designing a suitable frame is quite an issue here. The frame needs to hold the lens (preferably at an adjustable distance to focus), hold the PCB with the LCD on (also, preferably adjustable) and have enough room for extras (battery, touch sensors, additional PCBs etc…). I’m hoping to have two touch buttons on the left hand side of the glasses frame to allow user interfacing to the glasses.
For the glasses themselves, I’ve decided to mutilate a cheap pair of clear lensed glasses. They only cost me £1.49 so I wasn’t too bothered about breaking them. Using my Dremel, I cut the old lenses out and drilled two mounting holes for my 3d printed lens holder and the PCB. All sections of this prototype will be held together with thick copper wire though future prototypes will use an M2 screw.
Talking about 3d printing! For this project, I got my first ever design 3d printed! Using a service named 3d hubs, I was able to get some designs I made in FreeCAD 3d printed and delivered to my house for £5. I have access to 3d printers here where I live namely the Nottingham Hackspace and at university but for the hackerspace, induction is required and well… the university is useless at anything extracurricular. Therefore, the easiest and fastest option was to just get a dedicated person to 3d print it for me and send it to me in the post.
The lens holder and lens ring were the two 3d printed parts. Designing these two in FreeCAD was easy and the software is able to export STL mesh files, suitable for 3d printing.
3d printed lens holder
The lens holder was designed to hold the lenses that I got from the Google Cardboard package. The lip that is visible holds the lens in and a dedicated lens ring is inserted after the lens to keep it held in. In a more permanent situation, a smidgen of superglue would be used to keep the lens ring in though I’m not going to glue the lens in just yet.
Lens ring used to hold lens in lens holder
As can be seen, they’re both pretty simple designs and only took me an hour or so to design from start to finish. The results are actually pretty good and were printed at a resolution of 150um. This wasn’t quite enough for a good lip on the lens ring but thats not a big deal as it holds the lens in just fine regardless.
I’ve not received my PCBs from OSHPark yet (first time trying!) so I’ve only mutilated my glasses and assembled the lens holder with the lens, along with trying them on – of course!
A few angles for the glasses!
Hopefully my PCBs arrive in the next couple of weeks though my first exam is in two days (subsequently, my last is on the 25th so it should all be over in a flash…) so I’ll definitely be revising compared to anything actually fun. Keep tuned for more updates!