Mole Scale
For the 2024 Maker Faire, I decided to make a scale that measures in moles. I used an Arduino with a load cell and an HX711 amplifier to measure the weight in grams of an object. I then created a program in Python that allows users to interact with a Raspberry Pi using a touchscreen. The program lets users input the elements to be measured and displays the weight of the object in moles. This device has never been created before and could simplify the process of chemistry experiments and education by automating calculations involved in finding the moles of a substance.
Inspiration
It started with an off-hand comment in chemistry class. My teacher mentioned how convenient it would be to have a scale that could measure directly in moles.
This sparked an idea. Chemists and students constantly perform manual calculations: find the mass in grams, look up the atomic weights, calculate the molar mass, and then divide. This process is time-consuming and prone to human error.
​
I saw a clear opportunity to automate the entire process, creating a novel tool to simplify and accelerate chemistry experiments and education.
Evaluating Solutions
-
Option 1: Arduino + Keypad + Load Cell
-
Pros: Cheapest option.
-
Cons: A physical keypad for inputting elements (like "H2O") would be clunky. The UI would not be very user-friendly.
-
-
Option 2: Raspberry Pi + Touchscreen + Load Cell
-
Pros: A sleek, modern design with an intuitive touchscreen GUI.
-
Cons: The touchscreen display shield used most of the Raspberry Pi's GPIO pins, leaving no way to connect the HX711 amplifier for the load cell.
-
-
Option 3 (Chosen): Raspberry Pi (UI) + Arduino (Sensor) + Load Cell
-
Pros: The best of both worlds. The Raspberry Pi could run the high-level Python GUI, while the Arduino could act as a dedicated co-processor to manage the hardware sensor.
-
Cons: More complex and expensive.
-
Decision: I chose this "distributed" system as it solved all the technical constraints and would deliver the best user experience.
-
Final Product
The final prototype, built for the 2024 Maker Faire, successfully integrates the hardware and software components into a single, functional tool.
​
The device allows a user to:
-
Input any chemical element or compound (e.g., "H2O" or "C6H12O6") via the Python-based touchscreen GUI.
-
Place the substance on the scale.
-
Instantly see the mass converted to moles in real-time, as the software pulls live gram data from the load cell and performs the molar mass calculations automatically.
Reflection
Presenting this prototype at the 2024 Maker Faire was the true test. The positive response from students, teachers, and parents validated that the initial "spark" from my chemistry teacher was a real problem. Watching people use the GUI reinforced a core lesson: a technical solution is only as good as its ability to be understood and used by others.
​
The experience and user feedback directly inform my vision for V2.0:
-
Integrated Enclosure: Design and 3D-print a custom, all-in-one enclosure to house the exposed wires and components, creating a professional lab instrument.
-
Cost & Complexity Reduction: The positive feedback confirmed this as a viable classroom tool, but the $126 price is a barrier. For V2.0, I will focus on integrating the load cell directly with the Raspberry Pi to eliminate the separate Arduino, significantly reducing the final cost and complexity.
