Grilled Cheese Smart Box: Microcontroller And A Whole Lot More

The Smart Box uses a microcontroller (mcu), and a whole lot more, to keep fresh grilled cheese sandwiches hot, moist and crisp.

Fresh, tasty, warm grilled cheese sandwich

The Smart Box is an innovation that dramatically demonstrates two sometimes overlooked non-electronics aspects of MCU-focused projects that can require as much work as the electronics, if not more work. Those two non-electronics issues are:

1. Figuring out what you need the MCU to control.
2. Figuring out all the non-electronic hardware issues for the project.

The goal of the Smart Box designers was to create an environment that could extend the 'highly edible' lifetime of a fresh grilled cheese from seven minutes to at least thirty minutes. As Fast Magazine tells the story, the design team tried to find,

"...a way to extend the sandwich's woefully short shelf life. They discovered that each Melt had about seven minutes before going cold, leaving the cheese to congeal and making for a subpar grilled cheese-eating experience...the team looked far and wide for a food transport box that could maintain just the right temperature while striking the right balance between moisture and crispiness for 30 to 60 minutes at a time...what we realized is that if you maintained the temperature, and you had even airflow, and a way to get some of the moisture out of the product as it sat in the box, that it can hold a Melt for over 20 minutes and still meet temperature, moisture, and crispness guidelines."

Sandwich container with ridges and holes for hot air circulation

The first part of the MCU project had nothing to do with an MCU. Most products and design projects involving an MCU will start by figuring out how the product or project ought to work to achieve the project's goal. For the Smart Box, the goal was a good tasting sandwich. So the first part of that project was to determine what ambient conditions would keep the sandwich from getting cold and soggy. It was obvious the grilled cheese sandwich storage and transport unit would need heat. They would have to keep the temperature low enough so it didn't cook the sandwich more, but high enough so the cheese would be nice and soft. And the temperature would need to be uniform throughout the sandwich storage and transport unit. After experimenting with different conditions, and probably eating quite a few grilled cheese sandwiches, they found the right temperature (190 - 200 degrees F) and the right moisture to keep the sandwich tasting good.

The next step was to develop a combination of materials, shapes, heaters, fans, etc, that would maintain the necessary temperature and moisture for the sandwiches. Air flow was key, both throughout the large insulated food transport box and throughout the smaller sandwich containers that sit on the shelves inside the food transport box. The majority of this physical design and development work didn't focus much on electronics of the project, other than to keep the fan pushing air and to keep the heater warming up the air. The Fast Company article explained:

"...for any of this to work, the air had to circulate around the sandwich so that the heat surrounding it was constant, like a convection oven with size restraints...Here's how it works: It uses a hot plate made out of aluminum to keep everything warm. But since direct heat can burn its contents, it's covered with a shield while an internal fan ensures proper air circulation. The whole system is sensitive, so inside are sensors that monitor the environment for precise heat and humidity levels. A microcontroller is used to make small adjustments automatically, ensuring that the grilled cheese arrives at your door or desk nice and toasty."

Once the physical design of the box was mostly figured out, the electronics wizards started working their magic. They figured out what temperature sensors to use and where to put them. The fan power and controls were designed and the rest of the MCU functions were programmed.

I'm sure figuring out the sensors, controls, MCU and programming took much longer than the length of the above paragraph indicates. But for the grilled cheese Smart Box, there's little doubt in my mind that the design-build issues requiring non-electronics 'maker skills' or physical design knowledge took more time and brainpower than the MCU-related part of the project. The Smart Box illustrates why the Humboldt 'makers' who really enjoy MCUs also need lots of other types of knowledge or need to collaborate with others who have the non-electronics skills.

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