Head Mounted Displays
Originally Published on ActiveWirehead.com
February 18, 2015
In this segment of my DIY Wearables series I’m going to concentrate on ways to build a cheap Head Mounted Display(HMD) that you can use for a variety of platforms.
When I was a kid I used to watch shows like Beyond Tomorrow about cutting edge technology. Occasionally they would do a segment about Steve Mann or Thad Starner, two of the fathers of wearable computing. These guys have been building and using wearable computers since the 80’s and 90’s respectively. I always wanted to try it myself, but the display was a real stumbling block. I lacked the skill to build one from scratch and ready made displays were incredibly expensive. So I decided to shelve that idea for awhile.
Where to Start
Fast forward to 2013. When I first saw a Raspberry Pi I knew I was going to try and build a wearable out of it (more on that in the next article). At the same time, Google Glass had brought wearable computing to the forefront of the digital zeitgeist, so I decided it was time to take a fresh look at building an HMD.
A little research revealed that affordable video glasses had finally come to market, but they were still a little pricey for my limited budget at $150, and I wasn’t sure how I was going to convert one from being a set of glasses to a monocle display. So, as always, more research was called for. Finally I stumbled across a web page that explained how to use the monochrome HMD from a toy RC car as a composite display. I found one on Ebay for $30! The game was afoot.
When I got the car in the mail I was excited to start modding it, but I wanted to test its capabilities first so I spent a day or two just playing with the car and chasing my cats around the house. The display was pretty good for it’s cost, and even a low res monochrome display would work for my wearable Pi. The HMD was simple in design and would accept any composite video signal and display it as a slightly fuzzy black & white image. The Raspberry Pi has a build in composite video port, which is almost unheard of in modern computers, but the Pi designers wanted a user to be able to plug it into any TV and get started, just like the 8-bit computers of old, so the only tricky part would be adapting the toy car HMD to a Pi.
This turned out to be easier than expected. The HMD used a 3 pole ⅛” plug to connect to the remote control, just like a standard headphone plug. One pole was power (4.5v), one was signal, and one was ground. So all I had to do was connect the signal and ground to an RCA cable and connect some batteries to the power and ground poles. I had a headphone jack in my parts bin, and pulled the battery box out of a little flashlight that used 3 AAA batteries. The whole process was done in less than an hour and PRESTO, I had an HMD for my Pi.
I was pretty happy with this setup and was having a good time experimenting with my own wearable computers, and then Adafruit published this little article. Here, they had figured out a way to use the components from one of the cheap video glasses I had looked at before to make a color HMD with a 3d printed chassis. I ordered the glasses, but still needed access to a 3d printer. I didn’t have one yet but managed to find a website that connects makers with local 3d printers. Before long I had the parts and was able to get the whole thing together in an evening.
Both of these HMD versions are easy to make/modify and don’t require any coding. The resolution is pretty low, but you don’t need very high res for an HMD monocle. They may not be little and slick like a Google Glass, but for a maker who wants to experiment with wearables on the cheap they are great displays.
copyright 2015 Jason Benson