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project brief
project brief
During the Fall 2019 semester, as part of "Designing for the Internet of Things" course, I collaborated with Eileen Wang and Mu Jiun Shie to design a bespoke IoT product for an user of our choice.
Project Duration: 2 weeks (13th November, 2019 - 24th November, 2019)
background
background
Viha, our stakeholder
Viha, our stakeholder
Viha is a current graduate student at Carnegie Mellon, studying information security. She lives with 2 roommates in a Squirrel Hill apartment. One of the benefits of having roommates is that even if she forgets to buy milk, her roommates would help replenish. However, she doesn't want to always rely on her roommates.
Viha never wants to be out of milk
Viha never wants to be out of milk
Unfortunately, even when Viha does go grocery shopping, she often realizes that she forgot to buy milk only after coming back from the grocery store.
When visiting her home, we discovered that one of her favorite objects is her collection of fridge magnets. Her fridge magnets hold up important information and papers with sentimental value for her. We thought communicating how much milk is left could be a useful capability for a fridge magnet, as it lives in a very visible place at home. We also chose to create a fridge magnet because we want to add to her collection, instead of introducing an item that may feel unfamiliar to her.
Our goal
Our goal
Functionally, we want to create a device that can proactively remind Viha when her milk is running low, so she will remember to buy milk. Visually, the device should look like it is part of her home environment, and not like a foreign object.
Initial concept
Initial concept
A magical magnet that can tell Viha how much milk left.
We wanted to use the LED signal to present a different status of the milk volume. The fridge magnet will flash different colors depending on the amount of milk left.
Storyboard
Storyboard
schematic diagram
schematic diagram
Setting for 100% milk volume - 1 gallon, 1/2 gallon, or 1 quart
Sensor for showing current milk volume - green, yellow, red
Request for current milk volume- Milk level is XX%
Message - receive a notification when the milk volume < 25%
Prototype
Prototype
Design Approach:
Design Approach:
Magnet size:
We decided that the device needed to be big enough for Viha to see the neopixel color feedback clearly, but small enough to still feel like a magnet.
Size of neopixel:
It should be big enough so that Viha can see the colors clearly close up as well as when she is 80'' away (glancing at the fridge on her way out the door).
Visual design of the milk carton:
From observing the items Viha has in her room, she likes objects that are cute and animated-looking. This inspired us to take on a cartoon-y aesthetic for the visual design of the milk carton.
Engineering Approach:
Engineering Approach:
To enable the fridge magnet to detect the milk, we used a bar type load sensor. The load sensor with a maximum rated capacity of 5 kgs was chosen as a typical one gallon milk carton weighs at around 4.3 kgs. To detect the level of milk in the fridge, the sensor reads the instantaneous value every second and publishes that to the cloud. The fridge magnet subscribes to the event and sends signal to the neopixel to display different colors as mentioned in the schematic diagram as shown above. A 1200 mAh LiPo battery is connected to the neopixel circuit.
Components:
Components:
- Particle Argon
- Neopixel Stick
- Bar type of load cell
- Load Cell Amplifier HX711
- Magnet
- Li-Po Battery
Source code for the load sensor:
Source code for the load sensor:
Source code for the fridge magnet:
Source code for the fridge magnet:
Visiting Viha to gather feedback & Iterating Milk box
Visiting Viha to gather feedback & Iterating Milk box
We learned that Viha frequently buys 1 gallon of milk, but sometimes there are times when she has to settle for smaller volumes if the gallon milk runs out at the grocery store. This made us realize that we need to calibrate the scale to address low, medium, and high volume for each of the carton size she could buy. The 2nd feedback was she always places her milk on the bottom shelf. The wiring between the fridge magnet and load sensor stretched across the fridge shelves, making it inconvenient for her to reach items. In our next iteration, we will try to make the load sensor wireless. Lastly, Viha doubted whether the load sensor is sturdy enough to sustain the weight of a gallon’s milk. From a function perspective, the load sensor works well with a gallon, but we might make it look wider visually to help Viha feel at ease.
Final Prototype:
Final Prototype:
takeaways from this project
takeaways from this project
- My individual contribution: Designing and coding the algorithm, fabricating the prototype
- Always look for simple and instinctive ways of communication between the IoT products and humans as they will be able to glance for information instead of paying lot of attention.
- Think simple and include functionality that add value to the experience of using the enchanted object.
- Prototype with different form, function and materials to achieve your goal.
- Skills learned: working with load sensors, output components like neopixels , sharing sensor information on the internet through the Cloud API and allowing user interaction through web services like IFTTT.
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