RoboHeart Part 4

The robot sculpture had a red plastic heart that needed to be replaced if I wanted the heart to be other colors.

Original Heart

A translucent white plastic would be ideal for this – like ABS, which can be printed on a MakerBot Cupcake CNC. And we happen to have one of those at CRASH Space.

I used calipers to measure the heart’s dimensions, and used photo references to model the heart for printing. The heart pokes through an egg-shaped hole in the front of the robot’s chest, and on the inside, was a block that was glued to the inside.

Blender has a feature where you can import an image file into the background of a view and use it as a reference for your model. This only gets you one view, but it’s a good start.

Here’s the 3D model in Blender:

3D Heart

I needed the wall of the heart through which the light shines to be as even as possible, so I made the heart hollow. This means that the entire underside of the heart is an unsupported overhang (which the MakerBot doesn’t handle well), but it printed pretty well despite this.

Printing The Heart

Printing The Heart

MakerBot printed objects have a distinctive layered look to them, which is cool and all, but it lacks a certain polish. Acetone is an ABS solvent, so a quick soak in acetone smoothes out the layer details and gives it a nice sheen. Here’s what it looks like before and after:

Printed Hearts - Raw And Soaked

The heart was held in place inside the robot with rubber cement like adhesive, which took some effrot to remove. It turned out that the interior block was a separate piece of clear plastic that was scuffed (sand blasted?) on the inside as a diffusion. Had I known that, I might have incorporated it into my design. But I waited until the last minute to disassemble the robot to avoid tipping off the missus with a gaping hole in the front of her art robot lamp.

Getting the LEDs mounted behind the heart was difficult. I was planning on printing a support structure to attach the BlinkM behind the heart, but the MakerBot broke before I could. So I decided to use 50mm M3 bolts and 25mm nylon spacers. Unfortunately, the BlinkM boards do not have mounting holes for some odd reason, so I drilled some. Then I drilled corresponding holes in the heart and countersunk those holes to hold the socket cap M3 bolts.

Mounted BlinkM

When put together with the Arduino, it looks like this:

Heart, BlinkM, Arduino

Time to install in the robot!

I had always planned to use Household Goop to afix the heart inside the robot, even before I knew that was essentially what Mr. Bauer used to attach the original. It holds just about anything, but is removable in the event that I had to restore the sculpture to it’s original state. I sued it on my loop machine project to hold the speaker in place.

The sculpture is made of metal. Which could short out electronics that come in contact with it. So I taped up the bottom of the Arduino with blue painters tape to keep the bottom of the board from shorting out on the inside of the robot.

Insulated Arduino

My plan was to use a long USB cable in place of the AC cord. The USB connection will carry 5 volts DC to power the Arduino, which then powers the BlinkM. So, we don’t need the AC cord. The “A” end of the USB cable diesn’t quite fit through the AC cord hole, so I had to trim down the plug shroud and drill out the hole a bit.

Once I got everything inside the robot, I realized that the controller board was in the way of the rod that held the robot together. So I had to separate the BlinkM and it’s controller, using more of the jumper wires that connected the BlinkM controller to the Arduino. This took six more jumpers, so I ended up using a total of ten.

There was plenty of room inside the robot, but there were enough constraints to make the arrangement a bit of a challenge. Nothing could block the central vertical rod that holds the robot together, and the horizontal rod that holds the arms in place got in the way. And, of course, nothing could block the LEDs themselves.

Here’s what it looks like on the inside of the robot:

Inside The Robot

Plugging the USB cable in to any powered USB port causes the heartbeat sequence to start on the BlinkM. We want more than that.

Read more in part 5.

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