The Cyclopean Eye

The tiniest springs I could find in my "this could be useful" parts bin

The eyes are an important means of expression of the "soul" of a person, animal or character. The only external organ that connects directly to the brain through the shortest possible path.
The eyes of the creator move nervously as he scans its surroundings. Its world. They are animated by a simple spring mechanism that responds to the smallest movement. I did not know it was going to be so challenging to do this, except that, as we have found out, scale matters. And the smaller the scale the more critical the elements become.

The springs proved to be too weak to support the weight of the eye,
so I added a coat of latex to strengthen and stiffen it a bit,
but it proved to be a little too much so I ended up burning the latex away.
The residue that it left iwas just the right amount.

Lorena irritating the eyes

Of course the real "eye" of the Creator is up in the sky, or rather the ceiling in this case. This cyclopean eye that sees and controls everything is more and more a pervasi and accepted fact of life, in our streets, our buildings and even our homes, not to mention the "real" and inaccessible eye in the sky who observes and analyzes our every move, both as a species as well as individually when the need arises.

A very wide angle camera (76 degrees) was the choice after a good deal of research, and it proved to be the right one. I like that it is flat and although the base actually sucks if you are going to use it on a desk or a monitor it is perfect to tape to the roof and adjust the angle precisely. I needed a wide angle because the ceiling at the venue is not very tall and the camera must cover at least a 10x10 mt performing area, the world of the Creator, its Tartarus.

HP 2 megapixel camera, 76 degrees FOV

Related to the eyes or rather vision system is the light. Not the infrared light that the camera detects and processes but the actual "stage lighting". For quite a while I thought I was going to have to finagle a small lighting system form the theatre department at my university but since that was not very promising I started looking around for solutions.

I must say I am very happy with the outcome. I bought some inexpensive 12 LED flashlights at the local supermarket and hacked them (literally) so as to keep only the front portion. The advantage, in this case, of a cheap Chinese product is that it was very easy to solder to it, unlike more sophisticated models. The beam is extremely bright and is easily controlled by the microcontroller. So I have 4 "spots" with different color lights (a color filter on the LED's) to dramatize the scene and automatically create different moods according to the moment.

I got the plastic flexible contraption to where I attached the light base from one of my many "possible useful things" boxes. I wish I knew what it is or where it came from, maybe someone does becasue it is extremely practical for this and I am sure, other, applications. I suspect that it might belong to some fluid dispensing system.

The following are the very first tests with my new lighting system. I love it! absolute and precise positional and intensity control.

IR Beacon

This is the first finished beacon. It has 24 IR (infrared) LED's. The idea was that, since the tracking camera must have a wide angle in order to see the entire stage (which is about 6x6 meters, much smaller than I expected) from above, we needed an array big enough that would be easily tracked.

What I did not realize was that the angle of the LED's that I got was extremely narrow, so that when the performer lowers or tilts her head (the beacon is on top of her head) the LED's practically disappear. So we came up with the idea of using a diffusion dome to spread the light. That of course is half a ping-pong ball which happened to have the exact required diameter.

The ball was too thick and did not let enough light through, so I sanded it until it felt like a turtle egg, if you ever touched one. The solution worked, however there was still a considerable loss of light.

So I started to look for new LED's. This time I made sure that the lens of the LED would be wide enough to allow the free movement of the performer's head. This is what I found:

Ultra Wide Angle IR 850nm

These LED's are awesome. We could not believe how wide they emit light and how bright they are. You can almost turn the away from the camera and you can still see them!. So they will definitely do the trick without the need for a diffuser. We will use a set of ten which has the added benefit of resulting in a much smaller device and, because it is IR, it will be invisible to the audience.

I bought them form the guys at NaturalPoint which have a wide (yes, intended) variety of optical devices, mostly for motion-tracking. A set of ten cost me US$ 15 which is about half of the price of "cheap" LED's at RadioCrap.

So now we will design and burn another circuit and probably use a coin battery instead, to make everything really compact and unobtrusive to wear.

As soon as the UI (user interface) is ready for the tracking and motion-assigning program I will post pics of the UI and the tracking screen which is a lot of fun to see in operation.

The Exoskeleton

I have been literally immersed in a virtual reality. Working at a small scale forces you to adjust your senses and perception of self. Then you suddenly realize that somehow your fingers are too big, your body too clumsy, your eyesight not good enough to deal with a Lilliputian world. Fortunately our cyborgian self comes to the rescue and we make use of the many attachments and extensions that makes us makers of things, creators of our own destiny. (I might believe that someday...)

All the mechanics are functioning, at least by hand and in individual servo tests. It has been very hard to deal with some problems, most of which have to do with balance and friction, not of the marionette which is very fine, thank you, but of the mechanical elevator that raises and lowers most of the machinery so that the head can turn, the body express and the arms move while at the same time the Creator changes its position , kneel, stand up etc.

This problem is not so evident at first, specially if you are used to manipulate a puppet or marionette. Since your hand has a mind of its own it is hard to consciously realize tha amount of intelligence that it has to deal with all these complicated maneuvers. As you move the "plane" controller, pull the strings etc, you hand raises and lowers automatically and compensates this movement by tilting, rolling or yawing the controller.

Arm control assembly

Potentiometer as high precision encoder

However, when you have a fixed structure that supports the controllers it becomes evident that you need more than one motor to actuate on any given movement, because each movement influences the rest. Of course, as Dwiggins taught us, you should let gravity do most of the work, since she knows all about the laws of physics, but then there is the issue of correspondance, economy, efficiency and why not, elegance of design. Simpler is better. The complexity of simplicity.

Detail of the servo with its sturdy mounting plate

Assembled arm control with lead counterweight

Lead counterweight and potentiometer encoder

Give me a big enough lever...

The real servos finally arrived! here is the Hi-Tech HS-805BB Mega Giant Scale Servo being tested. I simply attached one of the many great horns and plates that it comes with to my fish-line spool, using its own screw and voilà! 19.8 / 24.7 kg*cm (4.8V/6V) of torque! It is temporarily held in place with straps as you can see because as you can imagine the square holes of the Vex plates don't line up with anything but their own stuff (I promised I would stop bitching about it!)

For the rest of the controls I am using the HS-645MG UltraTorque Metal Gear Servos that have 7.7 / 9.6 kg*cm (4.8V/6V) of torque, very much on the safe side.

On the left of the picture you see Vex's red optical encoder which I planned to use to determine the position of the continuous rotation motors that lift the arms, but again, not even the extremely versatile Make controller could recognize the simple signal. I am sure it can be done but why waste time. I ordered a set of high-res 10 turn potentiometers that are not only more precise but can "hold" the last position even when the power is turned off.

Divide and conquer?

That seems to be the design philosophy of the VEX guys. I promise (well, a weak promise) that I won't waste more time bitching about their horrible "close source" design decisions. But someone has to say something. Of course I used their stuff to prototype my project since I had bought 5 or 6 kits with the hope of actually using them for the final project. Now, to be fair, their nuts and screws are first rate and I have no complaints, as well as their cute chain transports if you use their square shafts of course, but the rest...


It was obvious pretty soon that the electronic/hardware side would not work due to their very flimsy nature and weak linkage (or lack of it). Take their servo for example. Not only is it far from standard, so that you cannot mix with any other brand, but it lacks fundamental elements like a horn or attachment plate of some sort so that you can drive something more than their absurd square shafts. Guess what, you cannot even screw anything to it, you can only use their "clutch" (the small cylinder with a short square stub) to attach another square shaft to drive any square holed device! BTW the clutch and therefore anything attached to it, will simply fall off if you turn it upside down. Am I missing a screw here?

You cannot see it in this next picture, but those arms or extensions that I need to drive the limbs of the marionette with have as much strength and stability as an apple stuck on the tip of a drinking straw and balanced on the edge of a glass, can you picture that? perhaps David Copperfield could use such a trick. The main reason being that as I explained, the servos connect to anything else through the wimpy clutch mechanism that cannot stand any side pressure, only direct transmission to a wheel at the most.


To be fair, after a great deal of literally hacking away with a saw, drilling and cutting and bending, I was able to put together a somewhat functional scaffolding for the stage. If I had the money I would simply make everything from scratch out of aluminum and some steel pieces. And, yes, chuck those servos away. I opened one to convert it, I was so shocked by the poor craftsmanship inside, probably built on a Chinese sweatshop (badly soldered by hand), that I just closed it and proceeded to order a set of excellent Hi-Tech servos.

Snap to grid

Serious construction begins. This has to be, want it or not, the last stretch of the building process for the Creator stage.

But before I begin this section I want to share a tip that I take for granted, but friends that see it are always amused by it. You know that when you work on a project involving dozens or hundreds of small pieces, screws, washers and what not, things like to go amiss. Lost socks pale in comparison, specially when you lose a servo screw that you won't find in any hardware store (unless you live in the Bay Area, how I miss that!). And ordering a screw or two online just does not cut it.

So, I use a big magnet block (which I don't remember where I got) and simply and literally throw all those little pieces at it, even from quite a distance and it just snaps them as they try to go by. Sometimes I am working on an odd position, (upside down ?) and as I disassemble something, which happens more and more often as I try to refine my design, I start collecting all these little pieces in my hand and mouth that are eager to disappear in the cracks of the floor or my stomach. Well, just toss'em up like a chef flipping pancakes towards the magnetic field and , snap! they are not going anywhere.

Now, mind you that this is not a very powerful magnet, like those neodymium or ceramic magnets that you find in hard drives otherwise getting a washer back would probably be impossible, but it is strong enough to hold quite a bit of stuff. Sometimes you cannot even see the magnet anymore, just a weird nut screwy sculpture. I'll add a pic like that so you can see it.