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A while back, I saw "The Most Useless Machine" by Instructables user Frivolous Engineering. This is a machine whose only function is to turn itself off. When you flip the power switch to turn it on, an arm pops out of the box and turns the power switch back off.

I love the hilarious absurdity of this project. So I decided to make some "useless" devices of my own. In this project, I am going to share with you how to make a "Useless Candle." Whenever you light this candle, it automatically blows itself out.

This is done with a simple light sensor and a small air pump. When the sensor detects the increased light from the candle being lit, it turns on an air pump. The air pump pushes air through a tube that is mounted to the candle holder and blows the candle out.

Step 1: Watch the Video

Here is a video walkthrough of the project.

<p>I love the concept - the absurdity of the 'useless machine' is great but this takes it one step further! Bravo!</p><p>You might want to look into using a low voltage solenoid and a 'mini bellows' instead of an aquarium pump and mains voltage. You could then keep everything low voltage on a single power supply and possibly all parts could be located on the candle holder.</p>
Is it possible to make this project using an arduino? And how? *sorry for the bad english
<p>Yes. It is possible. Use the same kind of light sensor. Then instead of connecting it to the capacitors and the 555 timer, just connect it to the analog input pin on the Arduino. Then write a code that looks for a certain voltage on that pin, have it wait for a set delay and then activate a relay driver that will turn on the air pump.</p>
Nice and Awesome idea...
<p>Ever seen one of these:</p><p><a href="http://www.amazon.com/SainSmart-Infrared-Detection-Sensor-Arduino/dp/B00K8PLGMI" rel="nofollow">http://www.amazon.com/SainSmart-Infrared-Detection...</a></p><p>?</p><p>It is a flame sensor, and it might work better than the photoresistor to avoid light interference and be less obtrusive and bulky. I have one and it works great. Just a thought. other than that, good project!</p>
Interesting idea. I may have to look into that for a future project.
<p>Nice! It could actually be a useful product if, say, you put in a timer and blew it out after a preset time (30 minutes? 1 hour?). My family likes candles but we forget to blow them out after we leave a room, creating a safety hazard. </p><p>Or maybe even put in a motion sensor like the lights that turn off if nobody's been in the room for some time, so the candle blows itself out if nobody's around.</p>
<p>Interesting project.</p><p>The exact opposite of a trick candle.</p>

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Bio: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker ... More »
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