Monday, April 21, 2008

Sense and sensibility and the Oneironaut

Visualizing the user interface for servo control

The nervous system is the current step (by step). Working on the sensors and on the beacons has given me a clearer understanding that there is nothing I know. Still very very far from The Docta Ignorantia.

Here is our microprocessor stack composed of two Make boards which were our final choice. The boards are highly integrated, very easy to interface and simply well designed. The only drawback was the limitation of 4 servo ports per board. I decided early on that 8 motors were as many as I wanted to use, both for practical and symbolic reasons. Four is the symbol of man generated by the trilogy which comes from the duality contained in the unity (bear with me, it is a stream of thought). 8 represents the power of the king in chess, and the queen in all her potency and (coming down to earth), I could only afford two Make controllers anyway! So, there. I had to do it with only 8 motors, period.

Then came the IR beacon circuit. That was a lot of fun to build although it took a lot of trial and error to do it with kitchen stuff. DYI instructions stipulate in no uncertain terms that you should use glossy inkjet paper and ONLY print with a laser printer, then iron transfer into the copper plate. Well, after many frustrating trials, botched plates and burnt fingers we (Philip and I) decided to try swhat you are not supposed to do. Went to our local print shop and had the circuit printed on their glossiest color laser paper with their fancy color printers. That worked beautifully. It transfered absolutely perfect the first time around. The entire coating of the paper stuck to the plate, and I am sure more than one has though that was wrong, but after soaking it in warm water the paper peeled off like a decal and left an impecable mask.

So here is Philip, which was the instigator of the whole DYI circuit idea cooking up the circuit with a coctel of muriatic acid mixed with hydrogen peroxide. In a few minutes our circuit was done. As usual he is multitasking with his totally hacked IPhone.

Guess where Philip is from...

Philip in my studio dremelin the circuit holes while Castro look approvingly at our socialist methodology.

He got a kick out of my retro-futuristic glasses. You look awful in them, but they have a variable focus that allows you to magnify minute stuff or read a newspaper across the room.

This section needs proofing and revising...tomorrow, after I give my class and deal with insane bureaucracy.

After dealing with the obvious and easy choices, like the arms (4 motors there) I realized the problem. My monster servo would lower the body, yes. But what about the head?, the shoulder strings? (they allow the marionette to turn the upper part of the body to face in another direction). They had to be lowered at the same time! otherwise I would need many more motors and complex programming to synchronize all these elements.

So the idea of the elevator was born, with all its ancillary problems, weight, friction, balance, stability, randomness, etc. At first I built tracks to guide the (square!) rods up and down. These rods (quads?) support a platform that houses the 3 remaining servos. The problem is that the head has more than one degree of freedom of course. It not only has to turn left and right, it also has to tilt sideways and bow as well. Or pitch, yaw and roll if you will.

All these simple motions are trivial (if difficult to master) in a marionette. Then I had the shoulder controls to turn the body around; how to do all that with 3 servos and control the wanted nuances?

After about two weeks (which is the time I have not posted!) I stumbled upon the solution, where but in a dream!. It is pretty obvious that we work as hard in our oneiric universe as we do in our waking world.

Next morning I skeptically went to examine the contraption with the suspicion that, like many other "great ideas" conceived in la-la land it would turn to be impractical, impossible or just plain turdy. It actually took me a while to connect my ideas with the reality of the mechanics, something was missing which I had apparently forgotten. Then, all of a sudden I saw it! make one of the servos perform double duty.

I cannot even explain how I visualized it. It was so obvious, simple, and yes, elegant. The only bummer is that I feel it did not come from me but from the collective unconscious debris. I just picked up the pieces.

I will post some pictures to explain how it works.

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