We’d seen it done with buttons, switches, gestures, capacitive touch, and IR remote, but never like this. [electron_plumber] made an LED that can be blown out like a candle, and amazingly it requires no added sensors. The project uses an Arduino to demonstrate turning a tiny LED on and off in response to being blown on, and the only components are the LED and a resistor.
How is this done? [electron_plumber] uses an interesting property of diodes (which are the “D” in LED) to use the LED itself as a temperature sensor. A diode’s voltage drop depends on two things: the current that is being driven through the diode, and the temperature. If the current is held constant, then the forward voltage drop changes reliably in response to temperature. Turning the LED on warms it up and blowing on it cools it off, causing measurable changes in the voltage drop across the device. The change isn’t much — only a handful of millivolts — but the effect is consistent and can be measured. This is a principle [Elliot Williams] recently covered in depth: using diodes as temperature sensors.
It’s a clever demo with a two important details to make it work. The first is the LED itself; [electron_plumber] uses a tiny 0402 LED that is mounted on two wires in order to maximize the temperature change caused by blowing on it. The second is the method for detecting changes of only a few millivolts more reliably. By oversampling the Arduino’s ADC, an effectively higher resolution is obtained without adding any hardware or altering the voltage reference. Instead of reading the ADC once, the code reads the ADC 256 times and sums the readings. By working with the larger number, cumulative changes that would not register reliably on a single read can be captured and acted upon. More details are available from [electron_plumber]’s GitHub repository for LEDs as Sensors.
Embedded below is a video that is as wonderful as it is brief. It demonstrates the project in action, takes a “show, don’t tell” approach, and is no longer than it needs to be.
More often than you think, scientific progress starts with a simple statement: “Huh, that’s funny…” That’s the sign that someone has noticed something peculiar, and that’s the raw fuel of science because it often takes the scientist down interesting rabbit holes that sometimes lead to insights into the way the world works.
[Ben Krasnow] ended up falling down one of those rabbit holes recently with his experiments with magnets and flames. It started with his look at the Zeeman effect, which is the observation that magnetic fields can influence the spectral lines of light emitted by certain sources. In a previous video, [Ben] showed that light from a sodium lamp could be dimmed by a powerful electromagnet. Some of his viewers took exception to his setup, which used an oxy-acetylene flame doped with sodium passing through the poles of the magnet; they thought the effect observed was a simple magnetohydrodynamic effect, and not the Zeeman effect he was supposed to be testing. That led to the experiments in the video below, which started with a candle flame being strongly deflected by the magnet. [Ben] methodically worked through the problem, eliminating variables by going so far as to blow soap bubbles of various gasses within the magnet’s poles to rule out the diamagnetism of oxygen as a cause of the phenomenon. He finally showed that even hot air by itself is deflected, using a simple light bulb and a FLIR camera. It’s good stuff, and well worth a watch.
Let’s face it, everybody wants to build a Stirling engine. They’re refined, and generally awesome. They’re also a rather involved fabrication project which is why you don’t see a lot of them around.
This doesn’t remove all of the complexity, but by following this example 3D printing a Sterling engine is just about half possible. This one uses 3D printing for the frame, mounting brackets, and flywheel. That wheel gets most of its mass from a set of metal nuts placed around the wheel. This simple proof-of-concept using a candle is shown off in the video after the break, where it also gets an upgrade to an integrated butane flame.
Stirling engines operate on heat, making printed plastic parts a no-go for some aspects of the build. But the non-printed parts in this design are some of the simplest we’ve seen, comprising a glass syringe, a glass cylinder, and silicone tubing to connect them both. The push-pull of the cylinder and syringe are alternating movements caused by heat of air from a candle flame, and natural cooling of the air as it moves away via the tubing.
We’d say this one falls just above mid-way on the excellence scale of these engines (and that’s great considering how approachable it is). On the elite side of things, here’s a 16-cylinder work of art. The other end of the scale may not look as beautiful, but there’s nothing that puts a bigger smile on our faces than clever builds using nothing but junk.
[AHNT] designed a printable sleeve that fits perfectly over 250mL cans. It provides a sturdy grid for poking tiny holes with a medical needle, and can be reused indefinitely with any pattern imaginable. He created two different printable bases to illuminate the lamp: one is sized to hold a votive candle, and the other is made for an LED strip circuit with a rocker switch and 12 VDC barrel jack. We suppose it wouldn’t take much to use an RGB LED instead—a Trinket or a Gemma would surely fit in the base.
In the video after the break, [AHNT] talks about prepping the can by cleanly removing the lid, which he does by filing the top edge until the layers separate. He also discusses a few methods for removing the paint, and notes that sandblasting worked the best.
It’s a great time to be a hobbyist. No matter how you feel about the Arduino/Raspberry Pi effect, the influx of general enthusiasm and demand it has created translates to better availability of components, a broader community, and loads of freely available knowledge. When people have access to knowledge and ideas, great things can happen. Tools that were once restricted to industrial use become open source, and the price of entry-level versions goes into a nosedive.
As we’ve seen over the last several years, the price of cheap 3D printers keeps falling while the bar of quality keeps rising. It’s happening with laser cutters and carving tools, too. Strolling through Microcenter a few weeks ago, I spotted a new toy on the back wall next to the 3D printers. It was LinkSprite’s desktop mini CNC. They didn’t have one out on display, but there were two of them in boxes on the shelf. And boy, those boxes were small. Laughably small. I wondered, could this adorable machine really be any good? To some, the $200 price tag suggests otherwise. To me, the price tag made it justifiable, especially considering that the next price point for a hobby CNC mill is at least twice as much. I took my phone out and stood there frantically looking for reviews, documentation, anything that was available. It seemed that the general, if sparse consensus is that this thing isn’t a total waste of money. Oh, and there’s a wiki.
According to LinkSprite’s wiki, this little machine will engrave wood, plastic, acrylic, PVC, and PCBs. It will specifically not engrave metal (PCB copper notwithstanding). I’m a bit leery of the chemicals used in the PCB etching process, so the idea of engraving them instead was especially tempting. I pulled the trigger.
Being a maker opens up so many doors in terms of ways to romance one’s partner through passion projects. If their passion is Disney films, then you may handily make them the enchanted rose from Beauty and the Beast for their birthday. Easy-peasy.
In addition to the love and care that went into this build, redditor [Vonblackhawk2811] has included a set of LEDs, salvaged from cheap flashlights and electronic candles, which are controlled by four toggle switches and offer multiple lighting selections — candlelight, soft white, colour cycling, and bright white — to appropriately set the mood. As if that wasn’t enough to romance his sweetheart, he’s also included an aux cord input and a pair of speakers so they may be serenaded by a tune or two as they dance the night away.
Liberal use of hot glue and duct tape are keeping the electronics secured, preventing any shorts. After all — what would it say if this gift went up in flames? An inspired stencil design — hand drawn and cut out — was used to apply a spray-on frosted glass finish to the cloche, and a romantic phrase was burned into the base, completing this heartfelt gift. The only quibble we have is that now we all have to step up our game in the courtship department.
One day there will be no more need for flames. [slider2732] has put yet another nail in the coffin of this most ancient of all technology by making a candle that uses a flicker LED that you blow out. A little more miniaturization and we’ll have them fully integrated into the size of birthday cake candles (Hint hint, hackers!).
You may have seen these candle flicker LEDs. They have a small chip inside them that modulates the LED’s light to flicker like a candle. We’ve even reported on what [Cpldcpu] found when he reverse engineered them first here and then here.
What [slider2732] did was to buy an electronic candle that used one of the LEDs actually shaped like a flame, and to drill a hole near the ‘flame’. He them embedded a microphone behind the hole. That goes to an LM386 amplifier circuit and from there to an Arduino Pro Mini all powered by a LiPo. As you’d expect, the Arduino code is very simple, just watch the pin from the amplifier and based on an internal variable, turn the LED on or off. We really like how none of the electronics is visible and how you actually have to lean over and blow into the top of the candle to blow it out. You can see this demonstrated in the video below.