Having the urge to make a ‘pointless invention’, I made a candle snuffer from a DC motor off an old helicopter, a 9V battery, and Erector set pieces. Basically, a fan blade attached to the motor and wired to a pushbutton sends a sufficient gust of air to blow out the flame of a small candle. I made two different versions of the snuffer, one with a only a 9V battery and one with an Arduino powered of a 9V battery, with the motor connected to 9V.
The snuffer basically has a little tray for a candle, with a fan pointed down at the top of the candle. A breadboard is mounted upright on the side, and the 9V battery is stowed under the tray. Below is a view of the whole thing lying on it’s side without the candle
Arduino Micro Candle Snuffer
When I first got the idea for a candle snuffer, I immediately thought using the Arduino Micro with a fan and allowing for time delays, temperature sensing for ‘overheat’ shutoff, and a photoresistor to detect if the candle is lit or not. The first thing I made was the breadboard mount and the candle tray out of Erector set pieces, and then I attempted to add the photoresistor, near the candle. However the heat from the candle would have likely damaged the photoresistor.
Getting the motor to spin fast enough to blow out the candle flame was a challenge with Arduino due to power constraints and transistor problems. I first tried direct drive off an Arduino pin’s 5V, but that did not make the motor spin nearly fast enough. Then I tried driving the motor with 9V via PNP transistor controlled by the Arduino, which, after a couple transistor overheats, still did not allow the motor to spin fast enough maybe due to voltage drops and such. My final version uses a 5V relay which seems to work really well. The fan spins more than fast enough using the relay. I’m not a huge fan (no pun intended) of relays because they can be difficult to wire and take up a lot of space on the breadboard. I had to tape my relay in place with my bright yellow electrical tape to keep it from popping out.
Because of all the frustration with driving the tiny little fan motor, I didn’t do much with the Arduino software side of things. You can check out the code I used here, which basically sends a gust of air at the candle flame when the button is held down. I didn’t add a time-delay or other sensing capabilities yet, though I may not because this is kind of already a benched project.
In my wiring, the 9V battery is connected to the Arduino’s Vin pin, and its ground is tethered to the Arduino’s ground. The relay turns on and off when it gets a signal from the Arduino. The fan runs off of the Arduino’s constant 5V pin. I’m not sure how this differs from direct motor drive from a pin, but the fan spins moves much faster.
Candle Snuffer Powered Off of 9V
Halfway through building the Arduino Micro version, I tore it all up and resorted to a pushbutton wired between 9V and the motor. When you press the button, the fan comes on and blows out the candle. I did look into using a 555 timer IC to try and create a 30 minute time delay until the candle is snuffed, but that ended up being a little complicated since I don’t have all the capacitor values. Ironically, this version of the candle snuffer does exactly the same thing as the Arduino Micro version.
The schematic is below. It’s quite simple.