Wednesday, August 22, 2012

Robot Pics

I pulled the circuits I wanted to save out of the robot.  But before I put it away for good, I took a couple of pictures.

To review; this was done on a tight budget and deadline.  What was needed was something that could be driven remotely out on stage, interact with one of the actors, and carry a live television camera (wireless).

Although I purchased a more expensive chassis, what was ready by opening night was built on top of a $40 toy store R/C car.

After I'd removed the original car body, I cut foam-core to fit around the wheels and suspension.  Then framed up a simple dome in foam-core.   I glued in scraps of extruded polystyrene (craft store "styrofoam") shaped, sanded, then covered with multiple coats of gesso and spackle to get a smooth surface.  Then painted with an epoxy spray paint.

It was strong enough to survive mild abuse (it got kicked several times on stage and ran into scenery a few times as well).  It was also extremely light -- the R/C car chassis couldn't support much weight.

The shell for the eyes were also carved out of foam.  Each had six high-power LEDs in three color circuits.  I fitted a disc of foam-core into the front of each "eye," then poked the legs of the LEDs through and secured each LED with a drop of cyanoacrylic (aka "super glue").  I soldered an individual ballast resistor to each LED, and brought each pair of resistors to center and connected them to the ribbon cable.  The positive legs of the LEDs were run around in a circle and tied together electrically.

On one eye, a miniature remote camera purchased on Amazon was hot-glued to the center of the disk, and a 9v battery connector spliced into the ribbon cable so it could be driven from the R/C car's rechargeable NiCads.

At the back of the head, the two ribbon cables from the eyes were spliced to the ribbon cable run through the neck and into the central body.  I had meant to dress these mostly out of sight but the props designer and the director both liked the look of the dangling wires.

Although it is hard to see from this picture, the eyes pivot (I had intended to add a servo here) on a modified PVC plumbing fixture.  A variety of PVC plumbing hardware carries down to the joint of the neck where it is secured with epoxy and insulation spray foam.  The eyes themselves ride on a quarter-inch threaded rod that was glued into place during final assembly.

The neck, incidentally, was a find.  While I was hunting for foam I discovered this paper-mach√© bust used for making a jewelry display.  It had an interesting shape I think worked very well.  The original concept, after all, was a Wall-E inspired "girl" robot with a sleek white shape.  The director really wanted binocular eyes, though, and the restrictions of the size and strength and wheelbase of the chassis meant it had to have a squat, low to the ground design -- and the result of all of these compromises and discoveries was a robot that many people described as "Wall-E and EVE had a baby."

After opening weekend it was requested that the eyes be able to turn off on command.  Well, that's why the ribbon cable was there.  I re-purposed an Arduino shield from a previous project, adding a ULN2803 to handle the 80ma or so of each LED color channel.  That top circuit board is a 424MHz four-channel radio receiver that I bought on eBay with matching keyfob transmitter.  Not as elegant as using one transmitter for the whole robot, but it worked.  The LEDs are on PWM pins and thus could be programmed to blink, pulse, color swirl, or chase.  However, since it was late in the day, the only functions used in the show were to turn the lights on and off.

Those LEDs were BRIGHT.  They were effectively the camera light.  Between the strange color (I ran only the blue and pink circuits during the show) and the often sketchy reception from the $25 wireless television camera, what the audience saw on the on-stage monitor was gloriously odd and colorful.

(Way, way down on my list of fun things to do is real-time video processing into an eye-stalk prop so it displays on connected monitor the same tri-color breakup shown in the George Pal "War of the Worlds.")

And there it was.  It could make it across stage on remote control, carry a functional camera, and flirt with an actress (the "voice" was done by an off-stage cast member through his existing wireless microphone, patched into a ring modulator emulated on the on-board DSP of our Yamaha digital sound board).

In the actual scene, the fill light was coming from a video projector hung out in the house, running a loop of television-set static.  This projector was also the first use of my MIDI-controlled projector douser!  But it proved hard to get decent pictures during the scene.  So the below are staged shots following closing night:

And, of course, I had to have one MORE Arduino in the show (there's an Arduino in the projector douser, interpreting MIDI signals and translating them into servo position).  And that was the Square Candies that Look Round.

Arduino, with a couple of micro-servos being powered off the USB connector (or the Arduino's on-board regulator), and a Sharp IR proximity sensor as trigger.  Next time I do something like this, however, I want to have a sticker or flyer or card to explain "Made with Arduino" and a link to that wonderful and artist-friendly hardware and community.

(There was a sheet of waxed paper on top of the box to make it look more candy-like but I forgot it when I swapped out an ailing servo on the last show weekend.)

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