Building a Vertical Touch Wall

01-08-2012

Welding

After watching the Mill Touch video and after Building my own touchtable, I've wanted to build a large touch wall of my own. Now that EMFCamp is not far away, we have a great oppotunity to build and test something in a field with a captive audience. So, without further ado, I've begun the herculian task of building this thing.

The Mill use a metal frame to hold a sheet of glass as a rear projection surface. Interference with lasers provides the blobs that can be tracked and turned into touches. Its a fairly simple thing to try but there are a lot of issues with this approach that boil down to filtering. First though, I needed to learn how to weld.

Thanks to my friend Hipster Chris and the London Hackspace, we managed to get our arc welding on. Down the road, One Stop Metal Shop provided a good stash of 30mm box steel. Carrying that all the way down to the hackspace was a bit tough but I managed it. Welding is a tricky task but it seems that if you prepare well, cleaning the surface, clamps and such, it goes a lot easier. The rest is practice and patience. Im quite happy with the result though.

Welding

So far, the glass has actually been the easiest bit. I went on ebay and bought a coffee table that someone didn't really want. I suppose I coul have checked freecycle otherwise. Removing the legs and corner braces left a perfect sheet of glass, frosted on one side. Brilliant. Tested with the hackspace projector, the colour and brightness are pretty good.

The lasers are the tricky bit. What is needed is a set of laser units that are safe (probably less than 10mW) and have a difraction grating to make a line, the wider angle the better. I've bought 6 from this chap on ebay and a filter from this bloke (which is apparently waiting in customs annoyingly).

I've tested the lasers and so far, things are not going too well really. One has to properly focus the gratings and my existing filter allows too much infrared through. Im using a PS3 eyetoy with the filter removed and an infrared camera filter that allows anything above 780nm to pass through. Sadly, that seems too much but hopefully the tighter filter will improve things.