An update on my latest project to build a robotic skull: Once the light bulb flashed and I started combining the JeVois machine vision camera with the cheapo plastic Halloween skull, notions of adding voice synthesis, head panning, jaw movement and a whole host of other cool capabilities flooded my consciousness.
It always works like that. Launch the idea, go out in the shop and fab-up a minimum functional prototype (MFP), then through the very process of “living” your project, you’ll get an avalanche of new ideas.
As Dr. Torq, I demonstrate and explain the very latest in physical computing technology. I encourage readers by example and we can do awesome things with cutting-edge off-the-shelf parts. Mounting the JeVois camera on a nondescript little table stand just doesn’t have the same effect as putting it into a crazy Steampunk robot skull, that immediately catches someone’s attention and compels them to say “What the heck is that?”
That’s the reaction we want. It can’t be superficial though. Interesting needs to go deep inside, too.
Today, we’ll continue talking about the internal framework of the skull. It will hold the camera in place, act as a mount for the Raspberry Pi “brain,” as well as the servo powering the jaw. The skull needs to be robust so it will survive the trip to and from my tech events, which sometimes includes domestic and international travel.
Flatten, Bend, then Solder
It didn’t make sense to simply mount the camera to the outside of the plastic skull. Once you perform a lobotomy, the skull no longer has any kind of strength and deforms easily. The camera would move all over the place during panning or when you pick it up. An internal frame is mandatory.
In the past, I simply cut and soldered the ends of brass tubing together. Worked great for square shaped badges. It made nice clean edges and corners, quite suitable for visible parts. But fabbing was exacting and time-consuming.
The skull face panels will hide much of the framework, so it made sense to try some different techniques, to speed up construction.
Flattening the ends of the brass tubing, bending the resulting tab to the right angle and then soldering it in place, proved a quick and workable approach. The technique came out pretty clean, with nothing that couldn’t be made more presentable with the Dremel and a sanding roll.
Take a look at the following pictures inside the skull:
Note that tying several intersecting endpoints together makes the connection easy to hold with alligator clips and clamps while you solder. My workhorse 100/140-watt Weller gun handled three to four tabs in one spot without any trouble.
Of course, you’ll have to spend some time figuring out where tubes should go for the best use of space inside the skull. Use triangulation to add rigidity. The 3/16″ brass tubing available at the hobby store is easy to solder and cut with a small plumber’s pipe cutter.
Put Your Thumbs into It
Notice that the front of the frame is form fitted to the inside of the skull.
You can bend thin-wall brass tubing without kinking with your thumbs. If you look at the following picture, there is just one little spot, right above the camera that didn’t come out as smoothly as I wanted.
Actually, it’s hardly noticeable. This is the first time I’ve used this technique.
I’ve read that some people use a spring or fill the tubing with sand to help it keep the shape. Certainly, we don’t want to mess up the bend because a three-foot stick of 3/16″ tubing runs about $4.
A 3″ or 4″ bend is certainly doable. Take your time and use your thumbs to bend a little at a time, checking frequently for fit. With practice, I might try the bending technique for visible frameworks, on upcoming projects.
I used a couple of pieces of tubing and flat stock to mount the camera sub-assembly. There is more bracing for the camera brackets and a bracket to be made for mounting the skull to a stand.
The stand will incorporate the pan servo and I’m thinking it might be fun to have the skull lie horizontally in a box during storage. Then, when I open the lid, a gear motor will raise it to the working, vertical orientation.
Ideas, ideas, too many ideas!
Naw, this brainstorming is really all great fun and will definitely spark a bunch of off-the-shelf hacker topics.
Once the hardware is fairly stable we can get into using the JeVois software, remote control, maybe a little automation and make the skull actually do things. Tune in next week!