Mindful Eating via Ambient Light

For the distracted diner who wants a subtle reminder to assess how full he or she is while eating, the MEAL dish is a weight-sensing dish that illuminates with colored light to give the user a sense of how much food has been eaten since the meal began. Normal dishware provides no feedback, placing the burden of self-monitoring entirely on the individual. Mealtime distractions pose less of an issue, however, when responsive MEAL dishes help people mind their own sense of satiety with subtle, pleasant cues via ambient light.

How It Works

1. Plug the Arduino into wall outlet and press the power button on the base unit to register the minimum weight of the empty dish. If desired, also plug the Arduino into a computer via the USB connector to view serial output during operation.
2. Fill the dish with food. 3 RGB LEDs that are located inside the base unit will pulse red when the minimum amount of weight has been added to enable subsequent monitoring.
3. Press the calibration button on the base unit to register the maximum weight.
4. Each of the dish’s three legs sits upon a load sensor. The sensors connect to the Arduino, which monitors the total weight sensed over time. As food is eaten from the dish, the Arduino translates the sensed weight change into a hue shift in the LEDs from red (a color shown to stimulate appetite) to blue (a color shown to promote relaxation). The parchment paper covering the base diffuses the light to produce a mild, colorful glow.

Construction

Materials

Base unit

• acrylic cement
• 1/8” acrylic sheeting
• craft knife with new blade
• cutting mat
• laser cutter
• long metal ruler
• parchment paper
• pencil
• tape, double-sided

Circuitry

• Arduino Duemilanove with USB connector and DC wall power adapter
• breadboard, wires, resistors, male headers
• BlinkM RGB LEDs (3)
• FlexiForce sensors (3)
• pushbutton momentary switches (2)
• soldering equipment

Dish

• 3-legged steamer basket

Steps

Base unit

1. Create a vector file of the design for the base unit pieces using vector graphics software such as Illustrator. The base will be a box of acrylic sheeting with (1) a square sheet for the top with 6 holes cut for the sensors, buttons, and bottom of the dish so that the light shines through brightly from the underside of the dish; (2) a square sheet under the top sheet with 3 holes cut for the buttons and bottom of the dish; (3) a bottom sheet half as wide as the top sheets. The bottom of the base is only half-enclosed so the Arduino and circuitry can be easily inserted and removed from the base; (4) four sides for the box. One side needs to have a hole large enough to accommodate the wires that exit the base.
2. Laser cut the pieces.
   
3. Measure and cut 4 pieces of parchment paper to cover the sides of the box. This will diffuse the light coming from the box. Adhere the paper to the sides with a minimal amount of double-sided tape.
4. Fit the box together and adhere the pieces using acrylic cement. (I wanted to be able to remove the sensors later, so I did not permanently adhere the top sheet to the rest of the base unit.)

Circuitry

The above wiring diagram describes the circuitry I used. Because I wanted to be able to reuse the load sensors after this project, I soldered wires to male headers, then plugged the sensors into the headers so I could avoid soldering the sensor pins directly.

Below is the assembled hardware:

Code

See the code for the MEAL Dish at GitHub.

I referenced libraries for a QueueArray and BlinkM.

Demo Day

On Demo Day, I set up the MEAL dish with some 1-pound quantities of chocolate and carrot sticks for people to weigh. Nearly everyone expressed surprise at how much a pound of food was – and outright shock at the news that we should be aiming to eat a pound of raw vegetables a day. Perhaps something like the MEAL dish could help people reach their daily target?

Other Explorations

I went through several iterations of construction over the course of this project. Initially, the ambient light came from a paper lamp I made out of illustrator board and bristol paper that was meant to sit on a tabletop beside the weight-sensing dish.

Based on feedback in class, I decided to incorporate the light source into the dish itself. My thinking was that the light changes would be more likely to be noticed and the entire system, having fewer pieces, would be more portable.

With the kind help of Hironori Yoshida and Madeline Gannon in the digital fabrication lab, I learned how to cast a dish out of polyester resin. Unfortunately, polyester is not a food-safe material, so I ultimately used a steamer basket in the final version.

Custom-made dish (not food-safe if made from polyester)

Materials

• CNC router
• 3” x 9” x 8” block of polyurethane high-density foam
• polyester resin, parts A and B
• PolyColor, white
• mold release
• safety equipment: goggles, mask, rubber gloves

Steps

1. Create a 3-D model of a two-part mold for the dish using 3-D modeling software such as Rhino. The bottom part of the mold will create the bottom of the dish with 3 legs. The top part of the mold will create the negative space inside the dish.
2. Carve the mold out of polyurethane high-density foam using a CNC router.
3. Coat the inside surfaces of the mold with mold release.
4. Mix polyester resin parts A and B in the specified ratios for the given product. Mix in a small amount of white pigment to create a translucent effect. Add a chemical accelerator if desired for faster cure time.
5. Fill the bottom half of the mold with the polyester resin mixture. Set the top half of the mold on top and weigh down with a flat, heavy object. Cure for 24 hours.
6. Demold the casting.

Download now or watch on posterous

IMG_0710.MOV (20993 KB)