Automatic Candle Extinguisher

The Plan

Welcome to episode 3 of "how can I make something really simple into a time consuming mess?" The idea was to create something that would blow a candle out after a certain amount of wax has burnt away based on user input. Basically, I intended to have a button that controlled a pulley made from a servo (push down to move, release to stop). That pulley would have a flame sensor attached to it, which would move down an unburnt candlestick to the point the user wishes it to be blown out. Then, the user would be able to light the candle, and the flame sensor would trigger the fan to blow out the flame once it reached the sensor.

Original Sketch

Changes

This original plan didn't account for a two things:

• The sensitivity of the flame sensor. Since the sensor detects infrared light, it would go off far before the wax burned down all the way. However, this was an easy fix; I planned to wrap black paper around the sensor to block the infrared light from reaching the sensor prematurely.
• How the pulley would actually work, and most importantly, how to attach the sensor without potential damage. Thankfully, this problem was solved through the previous one: the paper would block infrared light while also giving me a simpler cylindrical shape to attach to the string.
• Wires. WIRES.

Jumper Wires Are The Bane Of My Existence

It turns out that when you plan to use four components, the wiring gets a bit messy. I untangled, extended, and rewired this mess at least three times before the final result. This isn't super important to note, but just know that, if you're planning to replicate this (please don't), you're either gonna need a ton of jumper wires, or invest in longer ones. Or not be a baby like I'm doing and just deal with it.

Enclosure

Next came the question of building the device itself. I obviously wasn't going to have a repeat of last project's woodworking fiasco, so I brainstormed for a few days. After some thought, I remembered that I had some of these bad boys in my basement:

After collecting a few more materials and asking my mother if I could completely destroy my favorite childhood toy with hot glue, we were good to go.

I made pretty minimal changes to my original design, which was a nice change compared to my previous projects. This was what it looked like before I set up the pulley.

I ended up making a few changes to the setup from this image for stability purposes, and I also flipped the motor connection wires so that the fan turned in the opposite direction.

Final Prototype

Overall, I think that this project turned out okay! I had to get a little resourceful, but I ended up learning how to use a different type of motor while also semi-perfecting my servo pulley idea. Not too shabby. I had hoped to show a time lapse video of it working from start to finish, but my phone wasn't cooperating so I settled for the video below. I also included a bit about some of the absurd things I used to make this work.

I did end up needing to feed the flame sensor's wires through while the servo was turning and the sensor picked up on the candle far too early, but I didn't touch the project for about 15 minutes and it put out the candle, so it (technically) works.