Downing's Basement

Well Merry Christmas! Nearly two years to the day since the inspiration to take on a project like this first was ingrained, I’m finally calling this mini Air Hockey table “nearly” finished. And what a process this has been!

15 years ago, had someone told me I’d be even thinking of making something like this, much less actually pulling it off, I’d have looked at them sideways. But that’s what I love about this hobby. It allows even the craziest of ideas to actually stand a chance of becoming a reality.

The concept of the table is the same as real Air Hockey, however as is apparent, it is mini and is only about 1/5th the size of a normal Air Hockey table, and uses a 2.5″ puck vs the standard 3″.

Where things vary even more are its theme and play features. As you may have noticed, there are several references to the Doom Slayer all over the physical table as well as in the play features. So I guess you could call this a “DOOM” themed table.

The table operates in one of three play modes that are switched by the control panel on the side (seen below)

But we took this a bit further with the help of a composite video capture card, that not only grabs the screens output, but it also sends that signal down to the LED array on the table and recreates the video there…kind of.

So it should go without saying that this was probably one of my most ambitious projects I’ve ever taken on. Not just because I’d never attempted anything like it before, but also because I knew it wouldn’t be possible for me to do on my own.

That said though, aside from shelving the project for almost a full year, the way everything came together throughout the course of the build was, in my opinion, remarkable!

There were so many different types of materials, layers and fabrication methods used to make up the physical table, all of which would have to tie into one another perfectly. But knowing there would be soft automation, lighting and a physical/software combined user interface only added to the potential list of things that could go wrong. 

I had never really combined 3D Printing and CNC Machining the way I had to here. For example, when it came to mounting the side legs, the screws had to line up through 5 different parts and 4 different materials!

This made the 3D Modeling that much more imperative because being able to use the actual models to generate the cut paths for the CNC as well as the STL files for the 3D printed parts made life a great deal easier when it came to the physical assembly.

It was particularly handy when it came to parts like the table top that required actual printing as well. Having a defined cut path ahead of time gave me the boarders for the print so I wouldn’t cut anything off when I put the parent sheet on the CNC.

The Raspberry Pi was the second level of this build, which is pretty much where my usefulness ended. And as I mentioned in my video, I have to give a huge shout out my buddy CrashBash for taking the lead on this one, as his work not only brought the LED table to life but also gave the table its soft functionality for the score board and user interface.

And though the LED functions are awesome, the real benefit was the backend handling of the automation I wanted to include, like score detection/tracking and the play mode user interface. To make this work though, the Pi obviously needed some kind of way to receive input that either a goal was scored or the play mode changed. The play mode was pretty easy as they were just simple tact switches but the score detection was a bit more of a challenge.

I first had attempted to use simple lever arm limit switches for CNC machines, but getting them to trigger consistently in the puck traps was a bit of a problem. This is when I came across the IR LED Break Beam Sensors from Adafruit. These provided a more reliable solution, though is still not 100% as the traps were too wide for a single LED to cover. So two were wired up in parallel in each trap which I think sometimes causes a bit of confusion.

So that’s really just a taste of what went into this project and and I could go on and on about its features, but ultimately, I’m just amazed we were able to pull it off! Overall I’m very happy with how this came out especially with all the unknowns that both Crash and I were up against.

It’s still not perfect, we do have some emulation issues to work around and the score detection sometimes fails to count a goal which can be worked around easy enough, but other than that, I’m stoked to have this finally complete!

I’ve got several other projects well into development, so the first few months of 2024 are looking to be a good one! Thanks for checking this out and I’ll see you next time!