Daniel Leithinger

Final project for MAS 961 Techniques for Design and Fabrication.

After seeing harddrive POV display projects like Ian Smiths, I decided to give it a try and make my own using a broken harddrive and an Arduino controller.

Process:

1. Driving the motors: I first tried to find out how a brushless DC motor operates by probing the signal with a oscilloscope. It turned out they are more complicated to start up and control than I anticipated. Therefore I decided to use the built-in controller instead of designing my own.
2. Detecting the motor speed: I used a transmissive photomicrosensor, which consists of an infrared sender and receiver to detect a slot cut into the bottom platter of the harddrive.
   
3. I used surface mount RGB LEDs, which are convenient due to their small size:
   
4. To install the sensor and LEDs, holes were cut into the back of the hdd and the components glued in place with cables leading to the control circuit. Then the original motor control circuit was screwed back on to hold the cables in place and to run the motor:
   
5. This image shows a test of all LED’s turned on (red) with the upper platter not installed. The red circle highlights the location of the sensor. The white tape is at the location of the slot in the upper platter, so the LED’s are more visible:
   
6. The sensor input is analyzed by the Arduino microcontroller to determine the drive speed. The microcontroller then flashes the LEDs to display graphics. The following image shows the Arduino control circuit on a breadboard:
   
7. A slot cut into the spinning upper platter of the harddisk is used in conjunction with the flashing LEDs to display graphics on the device.
   
8. A video of the display showing a rainbow test pattern can be viewed here: http://www.youtube.com/watch?v=bNkj0Uc-hnU

Components:

• 3.5 inch harddrive
• PC power supply with 5 and 12V output
• Arduino Mini 3 with mini USB adapter
• Photomicrosensor: EE-SX1103 (Transmissive)
• 6 pc Full Color PLCC4 LED: OVSARGB3R8 (OPTEK Technologies)
• 3 pc MOSFET: 2N7000 N-Channel 60-V (D-S)
• Resistors: 6*470 Ohm; 12*240 Ohm; 1*330 Ohm; 1*50 Ohm

This post documents my attempt at creating a composite material which responds to light and magnetism and could possibly be used to increase the quality of camera-based tracking.

This is the first material the composite is based on Magne-View by Magnerite. (http://www.magnerite.com)

The second material is phosphorescent green by Golden Acrylics. I wanted to keep the Magne-View in mint condition, so I painted the phosphorescent color onto a clear sheet.

I thought the paint might be transparent enough for the Magne-View to come through, which turned out to be a wrong assumption:

Luckily, the green sheet is not completely opaque. Therefore, I tried to go the other way round and have the phosphorescent material shine through the Magne-View.

Here are strips of phosphorescent tape pasted to a sheet:

The flashlight reveals their glowing capabilities.

Final result: The phosphorescent material shines through the Magne-View, but only in very dark rooms (hence no photo of that). It would be interesting to add phosphorescent material to the Magne-View in the production stage, but I would have to investigate that further. Interesting and promising stuff nonetheless.

Assignment questions:

a. Does your composite support new and unique applications?
The composite could be used to increase the quality of 2D vision based motion tracking systems on surfaces. Due to the resulting visual patterns, the output of the material could also be used for artistic installations.

b. Can you design an interaction scenario around its ‘responsiveness’?
When a user draws on the surface with a magnet or a light pen, the material changes it’s visual characteristics. The visuals stay on the surface for a given time (phosphorescent material) or until a new stimuli is applied (magnetic film). This visual “trail” left on the surface can be utilized to increase the tracking quality when sensing input with a magnet or light on the surface with a camera.

c. How is it different from other technologies?
It is different from other camera based tracking methods, as the surface helps to increase the camera tracking quality, but has no active component.
The passive technology is used to support camera-based sensing with good results even when the tracking frame rate is low. The surface consumes no power.

d. Would it be possible to mass-produce it? How?
Use CES to learn about different fabrication processes.
I did not find the Materials used in the CES databank. However, as they are all commercially available, they could possibly be mass-produced:
- Magne-View ® Film: micro-encapsulated film
- Golden Acrylics: Phosphorescent Green paint
- Pro Tapes and Specialities Fluorescent Yellow Artist Tape
I would have to investigate the production process of Magne-View further to find out why it is green and if it can be mixed with other colors like the phosphorescent paint.

Assignment for MAS 962: Techniques for Design and Fabrication. Thanks to Adam Kumpf for the idea of using the Magne-View surface for tracking and for lending the materials.