Melissa Ma
Junior Mechanical Engineering Student @ University of Toronto | Engineering with a Purpose
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Smart Stovetop Knob
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SolidWorks | 3D Printer | Power Tools
Users may be preoccupied with their tasks on hand and are therefore unable to return to the countertop on time. This could lead to many inconveniences or even result in burnt food and housefires. The goal was to design and fabricate a device that would remotely turn off countertop knobs, without damaging the design space.
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3D Printed Gear (blue), which snug fits onto the existing stove knob; a timing belt connects the gear and the stepper motor
Knob that I will mount the smart knob on
Front view of system
Back view (power supply, wifi stepper module, and motor mount)
Isometric view of system
Smart Knob Ver. 2
To make the design more compact, portable, and self-contained, I utilized a ball-bearing design to turn the knob.
Exploded view of assembly
The outer housing of the ball bearing is fixed and sticks onto the stove via an adhesive. The inner housing rotates and is snug fitted onto the knob, which rotates together. The input is a NEMA 17 stepper motor, controlled by a Wifi Stepper Board (blue). Attached to the motor shaft is a gripper, which grips onto the knob handle and turns the knob. The motor is supported by two vertical columns in the outer housing, while the Wifi Stepper board sticks onto the inner walls of the outer housing via adhesives. Through this relative motion of the inner and outer housings of the ball bearing, the entire assembly is self-contained and turns the knob. Note that the wiring of the motor/wifi board/power supply assmebly is not shown in this animation. The power supply will connect to the entire assembly through a small opening on the side of the outer housing. This assembly can easily be accessed and maintained by removing the back cover.
Knob turning
Renderings
Role
​Mechanical Designer | Electrical Engineer | Technician
Project Highlights
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Designed system in SolidWorks (part, assembly, mechanical toolbox)
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Used Arduino, ESP8266 Wifi Module to control the NEMA 32 Stepper Motor, which drives the gear-belt system
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3D printed gears and fabricated motor mount with bandsaws, secured with bolts&nuts
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Programmed ESP8266 Wifi Module with Arduino code and web interface
Tools
SolidWorks | 3D Printer | Power Tools
Results/Lessons Learned
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Turned knob off remotely with 100% success rate
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When designing for flexibility, we can design a slot opening instead of drilling screw holes in fixed positions. This way, we would be able to tighten the screw wherever needed (in the case that you don't need that strong of a joint).
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Solidworks has many tool boxes - for example, the gear toolbox. This is a helpful tool to design gear systems (so that one does not have to design from scratch, like I did at the beginning of this project).
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There's always a tradeoff between the strength of the 3D printed part and print time. When the part doesn't have a high load requirement, we can reduce the print time by removing material in certain regions that does not significantly reduce the part's ability to bear load. For example, in the white motor mount shown above, we can remove some material from the face near the slots. At the same time, sharp corners can perhaps removed to reduce stress concentrators (in this case it was fine because the part did not have to support a significant load).
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I learned about what the different channels on a ESP wifi module (RX, TX, GND, and GPIO, etc...) and how to wire it with a stepper motor
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