Neopixels? Try Liquid Nitrogen To Color Shift Your LEDs Instead

November 11, 2023 by Dan Maloney 23 Comments

If you’re like us, you’ve never spent a second thinking about what happens when you dunk an ordinary LED into liquid nitrogen. That’s too bad because as it turns out, the results are pretty interesting and actually give us a little bit of a look at the quantum world.

The LED fun that [Sebastian] over at Baltic Lab demonstrates in the video below starts with a bright yellow LED and a beaker full of liquid nitrogen. Lowering the powered LED into the nitrogen changes the color of the light from yellow to green, an effect that reverses as the LED is withdrawn and starts to warm up again. There’s no apparent damage to the LED either, although we suppose that repeated thermal cycles might be detrimental at some point. The color change is quite rapid, and seems to also result in a general increase in the LED’s intensity, although that could be an optical illusion; our eyes are most sensitive in the greenish wavelengths, after all.

So why does this happen? [Sebastian] goes into some detail about that, and this is where quantum physics comes into it. The color of an LED is a property of the bandgap of the semiconductor material. Bandgap is just the difference in energy between electrons in the valence band (the energy levels electrons end up at when excited) and the conduction band (the energy levels they start at.) There’s no bandgap in conductive materials — the two bands overlap — while insulators have a huge bandgap and semiconductors have a narrow gap. Bandgap is also dependent on temperature; it increases with decreasing temperature, with different amounts for different semiconductors, but not observably so over normal temperature ranges. But liquid nitrogen is cold enough for the shift to be dramatically visible.

We’d love to see the color shift associated with other cryogens, or see what happens with a blue LED. Want to try this but don’t have any liquid nitrogen? Make some yourself!

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Pimp The Potentiometer

November 11, 2023 by Al Williams 23 Comments

Sometimes, a hack isn’t really about the technology but about the logistics. If we asked you to light up an LED using an Arduino, there’s a good chance you’d know exactly how to do that. How about a bunch of LEDs? Simple. Now turn on LEDs proportional to an input voltage. A little harder, but nothing that you probably haven’t done a million times. Finally, arrange the LEDs in an attractive circle around a potentiometer. Wait, how are you going to do that? [Upir] shows us a ready-made ring light for just this purpose and you can see the beautiful thing in the video below.

We made the LED things sound slightly easier than it is. The ring light has 31 LEDs but only 12 pins, so there is some multiplexing going on. The modules come in pairs for about $20, so not a throwaway part, but they will really dress up anything that needs a knob of any kind.

Naturally, it doesn’t matter what you use to drive the LEDs. You could track a pot or a rotary encoder. Or you could show microphone levels or something else. After all, it is just a bunch of LEDs. For that matter, they’d probably make a good pair of robot eyes. Let us know what you want to use them for in the comments.

If your significant other is a little geeky, you might want a different kind of ring light. We couldn’t help but wish the LEDs on the ring were addressable. That would open up a world of interesting possibilities while reducing the pin count, too.

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3D-Printed LED Wall Clock Does Lots With Little

November 6, 2023 by Richard Baguley 14 Comments

This wall clock built by [Alf Müller] is lovely, using two NeoPixel rings to mark the time by casting light onto a 3D-printed ring. The blue shows the minutes, made more discrete by a grid inside the ring. The green shows the hours. [Alf] has provided the code so you can rework the color scheme. It might be interesting to add seconds with the red LEDs, or perhaps a countdown triggered by a touch sensor…

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A Tiny Board For Driving LEDs In…Whatever

October 26, 2023 by Lewin Day 19 Comments

Whether you’re into chiptune or just playing Tetris on original hardware, you might like rocking a heavily-customized Game Boy. Lovely flashing LEDs can only improve the aesthetic, so if that’s what you’re after, you might consider the ARCCore board from [NatalieTheNerd].

The board is a compact and easy way to drive some addressable LEDs, with a form factor designed to take up a small amount of space when stuffed into a Game Boy or other game console. It rocks an RP2040 microcontroller set up to drive a strip of WS2812B LEDs. Three buttons are used to configure the color and brightness settings. The board is designed to run on 3.3 to 5 V, thanks to an onboard buck converter. It’s capable of delivering enough juice to run up to 10 RGB LEDs, though you could potentially use more if you ran them from external power.

You can use just about any microcontroller on the market today to run addressable LEDs if you so desire. If you want a compact drop-in solution that takes up less space, though, you might find the ARCCore useful. If you’ve got your own nifty kit for running addressable LEDs, don’t hesitate to share it with the broader hacker massive — hit the tipsline!

Giant LED Matrix Fills Blank Space In The Kitchen

October 9, 2023 by Richard Baguley 8 Comments

We’ve all got one: a blank space somewhere in our home that we don’t know what to do with. [James Miller] had one above his kitchen cabinets, so he filled it with a giant LED matrix. The result is a large but surprisingly attractive LED screen that can send messages, provide illumination, or while away the idle hours of the night playing Conway’s Game of Life.

[James] built the matrix using the usual suspect for these builds: several strings of WS2812 lights . He initially ran this from a Raspberry Pi, but realized that there was no need for such a dizzying amount of computing power, so he switched to an ESP32 instead. The frame is built from wood and foam board.

The first version he built used a fabric diffuser, but after a close encounter with a flaming steak, he switched over to commercial ceiling light diffusers cut down to size. We might have been tempted to keep going and try an “egg crate” style ceiling light panel for a the smaller pixel size, but [James] thinks he has reached the “good enough” point of this project. It’s certainly a fun build, and it looks very cool with minimal materials.

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Time And Tide Are One Thing

September 19, 2023 by Kristina Panos 3 Comments

The rise of 3D printing has given us incredible things, from awesome tchotchkes to intricate chocolates to useful things like spare body parts. But none has been so vital to comedy as say, printing hats for sea urchins. That’s right, sea urchins like to cover up with various things and will happily don, say, a 3D printed hat if presented the opportunity.

So anyway, this is a tide clock that uses a printed sea urchin and various hats to tell the time until/between low and high tide. How? It uses the position of a given hat relative to a couple nOOds LED strands, one for high tide and another for low.

Inside the large bamboo enclosure is an TTGO that fetches cheaply-obtained tide information and displays it on the screen. The TTGO also controls a servo that moves the sea urchin around. As it moves, a magnet in the urchin’s head (?) attracts the next hat.

Before settling on the current design, [rabbitcreek] experimented with both a sand dollar and a sea urchin skeleton. All the files are available if you want to whip up your own.

This isn’t [rabbitcreek]’s first foray into tide clocks. Here’s a solar number that should last for years.

Printed Upgrades Improve Cheap Digital Microscope

September 19, 2023 by Bryan Cockfield 7 Comments

Digital microscopes used to be something that only labs or universities might have, but as image sensor technology has progressed, the prices have fallen to the point that any classroom or hobbyist can easily obtain a usable device. The only problem is that a lot of features and quality have been lost to make some of these digital microscopes more affordable. In an effort to add some of these creature comforts back into more inexpensive devices, [Marb’s lab] has created a special carriage for one of these microscopes.

The first addition to the microscope is improved lighting. To accomplish this, three LEDs were built into custom housings and wired to a purpose-built LED driver board coupled with a voltage regulator. Two of the LED housings were attached to the end of adjustable arms, allowing them to be pointed in whichever direction is needed. The third is situated directly below the microscope underneath the stage. These are all mounted to a large, sturdy PVC base which also holds an adjustable carriage for the microscope itself. This allows much more fine-tuning of the distance between the sample and the microscope than it otherwise would have had.

For just a few dollars and a little bit of effort, the usability of a device like this is greatly improved. If you want to take the opposite approach and really go all-out for your microscope, though, take a look at these microscopes used for PCB circuit construction and troubleshooting or even this electron microscope for viewing things at a much higher magnification than any optical system would allow.

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