"The Great Resistor" color code illumination project

The Great Resistor Embiggens The Smallest Value

November 5, 2022 by Dave Walker 29 Comments

With surface-mount components quickly becoming the norm, even for homebrew hardware, the resistor color-code can sometimes feel a bit old-hat. However, anybody who has ever tried to identify a random through-hole resistor from a pile of assorted values will know that it’s still a handy skill to have up your sleeve. With this in mind, [j] decided to super-size the color-code with “The Great Resistor”.

Resistor color code from Wikipedia with white background — How the resistor color-code bands work

At the heart of the project is an Arduino Nano clone and a potential divider that measures the resistance of the test resistor against a known fixed value. Using the 16-bit ADC, the range of measurable values is theoretically 0 Ω to 15 MΩ, but there are some remaining issues with electrical noise that currently limit the practical range to between 100 Ω and 2 MΩ.

[j] is measuring the supply voltage to help counteract the noise, but intends to move to an oversampling/averaging method to improve the results in the next iteration.

The measured value is shown on the OLED display at the front, and in resistor color-code on an enormous symbolic resistor lit by WS2812 RGB LEDs behind.

Inside view of the great resistor showing WS2812 LEDs and baffle plates — Inside The Great Resistor, the LEDs and baffle plates make the magic work

Precision aside, the project looks very impressive and we like the way the giant resistor has been constructed. It would look great at a science show or a demonstration. We’re sure that the noise issues can be ironed out, and we’d encourage any readers with experience in this area to offer [j] some tips in the comments below. There’s a video after the break of The Great Resistor being put through its paces!

If you want to know more about the history of the resistor color code bands, then we have you covered. Alternatively, how about reading the color code directly with computer vision?

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DIY Arduino Hearing Test Device

October 23, 2022 by Dave Walker 18 Comments

Hearing loss is a common problem for many – especially those who may have attended too many loud concerts in their youth. [mircemk] had recently been for a hearing test, and noticed that the procedure was actually quite straightforward. Armed with this knowledge, he decided to build his own test system and document it for others to use.

audiogram showing the results of the arduino hearing test device — Resultant audiogram from the device showing each ear in a different color

By using an Arduino to produce tones of various stepped frequencies, and gradually increasing the volume until the test subject can detect the tone, it is possible to plot an audiogram of hearing threshold sensitivity. Testing each ear individually allows a comparison between one side and the other.

[mircemk] has built a nice miniature cabinet that holds an 8×8 matrix of WS2812 addressable RGB LEDs. A 128×64 pixel OLED display provides user instructions, and a rotary encoder with push-button serves as the user input.

Of course, this is not a calibrated professional piece of test equipment, and a lot will depend on the quality of the earpiece used. However, as a way to check for gross hearing issues, and as an interesting experiment, it holds a lot of promise.

There is even an extension, including a Class D audio amplifier, that allows the use of bone-conduction earpieces to help narrow down the cause of hearing loss further.

There’s some more information on bone conduction here, and we’ve covered an intriguing optical stimulation cochlear implant, too.

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A 3d printed ghost next to the base of an LED tea light that has 4 LEDs poking out and the IR receiver port and micro-USB connector showing.

A Cold Light To Warm Your Heart

October 9, 2022 by Abe Connelly 1 Comment

Halloween is coming fast and what better way to add to your Halloween ornamentation than [Wagiminator]’s cute NeoCandle tea light simulator.

[Wagiminator] has modified a 3D printed ghost along with extending [Mark Sherman]’s light simulation code to create a cute light that’s perfect for the holiday season. The NeoCandle uses an ATtiny85 chip to power four WS2812 NeoPixel jelly bean LEDs. The device has an infrared (IR) receiver to be able to control it from a remote that speaks the NEC protocol. There is a light sensor that allows the unit to dim when it detects ambient light and the whole unit is powered off of a micro-USB connection.

The ATtiny85 have limited program flash and [Wagiminator] packs in a lot of functionality in such a small package, squeezing in a bit-banging NeoPixel driver in only 18 bytes of flash that can push out a transfer rate 762 kpbs to update the LEDs. The pseudo-random number uses a Galois linear feedback shift register and comes in at 86 bytes of flash, with the IR receiver implementation code being the largest using 234 bytes of flash. The ATtiny85 itself has 8 KB of flash memory so maybe it’s possible to push [Waginminator]’s code to even more restrictive Atmel devices in the ATtiny family.

With microcontrollers and LEDs becoming so cheap and ubiquitous, making realistic flames with them is becoming accessible, as we’ve seen with previous projects on electronic candles.

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three sensory bridge audio spectrum analyzers, one in use with a lit LED array plugged in, the other facing the camera and leaning against the third, all on a table

The Sensory Bridge Is Your Path To A Desktop Rave

September 26, 2022 by Abe Connelly 7 Comments

[Lixie Labs] are no strangers to creating many projects with LEDs or other displays. Now they’ve created a low latency music visualizer, called the Sensory Bridge, that creates gorgeous light shows from music.

The Sensory Bridge has the ability to update up to 128 RGB LEDs at 60 fps. The unit has an on-board MEMS microphone that picks up ambient music to produce the light show. The chip is an ESP32-S2 that does Fast Fourier Transform trickery to allow for real-time updates to the RGB array. The LED terminal supports the common WS2812B LED pinouts (5 V, GND, DATA). The Sensory Bridge also has an “accessory port” that can be used for hardware extensions, such as a base for their LED “Mini Mast”, a long RGB array PCB strip.

The unit is powered by a 5 V 2 A USB-C connector. Different knobs on the device adjust the brightness, microphone sensitivity and reactivity of the LED strip. One of the nicer features is its “noise calibration” that can record ambient sound and subtract off the background noise frequency components to give a cleaner music signal. The Sensory Bridge is still new and it looks like some of the features are yet to come, like WiFi communication, accessory port upgrades and 3.5 mm audio input to bypass the on-board microphone.

The stated goals of the Sensory Bridge are to provide an open, powerful and flexible platform. This can be seen with their commitment to releasing the project as open source hardware, providing firmware, PCB design files and even the case STLs under a libre/free license. Audio spectrum analyzers are a favorite of ours and we’ve seen many different iterations ranging from ones using Raspberry Pis to others use ESP32s.

Video after the break!

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Throwback: Designing Addressable LEDs From Scratch

July 13, 2022 by Lewin Day 9 Comments

These days, addressable LEDs are all the rage. A little chip paired with each LED receives signals and modulates the light output as needed. [John Peterson] was working on a project along these very lines, designing his Curilights back in 2008!

[John] wasn’t the first to come up with the idea; he designed the Curilights to replicate a string of programmable LEDs he’d seen called Triklits. His design involved each RGB LED being fitted with a Microchip PIC 16F688 microcontroller, which could receive serial data and control the LED channels with PWM. These LEDs could then be strung up to create an addressable chain. It’s fundamentally the same concept as the WS2812, just in a larger format and built by hand. His design also had the benefit of non-volatile memory onboard the PICs, so animations could be stored even after power off. [John] later went on to build a controller for his lights, complete with sensors. It could be triggered by a motion sensor or light sensor, and would run animations on the string without the use of a computer.

While [John]’s design didn’t go on to bigger things or commercial success, it did win first place at the Third Annual Lantronix Wireless Design Contest. It also goes to show that many people will come around to the same idea when it makes good sense!

If you’re interested in the wider world of addressable LEDs, check out our breakdown on some of the products out there. Meanwhile, if you’re brewing up your own flashing, glowing projects, be sure to notify the tipsline!

Three flowers in a corner of a darkened room, shining in different colors.

LED Flower Bouquet Is A Radiant Hacker Desk Decoration

March 15, 2022 by Arya Voronova 4 Comments

[Jeremy Cook] writes to us about a project of his – a bouquet of LED cube flowers. The flowers are PCB cubes made out of small castellated PCBs, each of those having an individually addressable LED in its center. Castellations hold the cubes together mechanically, and thanks to a cleverly chosen pinout, only two different kinds of PCB need to be ordered for building such a flower!

As a vase for these flowers, he decided to use a glass bottle – which would need a cutout to fit a ESP8266-powered NodeMCU board, a controller of choice for the project. After a few different approaches for cutting glass all resulted in the bottles cracking, he gave up on the “clean cut” idea and reused one of the broken bottles, gluing it back together well enough for the aesthetic to work.

[Jeremy] tells us that he’s had help from a hack we covered back in 2017 – using a diode for level shifting, as the ESP8266’s 3.3 V level signals aren’t a good match for WS2812 inputs. From there, the WLED firmware for the ESP8266 ties everything together beautifully. It’s clear that [Jeremy] had a field day designing this, toying with all the ideas and approaches!

Colorful LEDs are a must-have for decorating hacker homes. From a bouquet of flowers, you might find yourself sketching a castellated PCB tile design, and next thing you know, you’ve created a beautiful system of LED triangle tiles. Some PCB fabs scoff at castellations, and if that’s the case, you might as well finish the job yourself.

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Image showing differences between WS2815 and WS2813 LED strips - the WS2815 strip lighting is more uniform throughout the strip's length.

Teaching You Everything You Might Have Missed About Addressable LEDs

February 27, 2022 by Arya Voronova 11 Comments

Often, financial motivation results in people writing great educational material for hackers. Such is absolutely the case with this extensive documentation blog post on addressable LEDs by [DeRun]. This article could very be named “Addressable LEDs 101”, and it’s a must-scroll-through for anyone, whether you’re a seasoned hacker, or an artist with hardly any technical background and a desire to put LEDs in your creations.

This blog post is easy to read, painting a complete picture of what you can expect from different addressable LED types, and with apt illustrations to boot. Ever wonder which one of the addressable strips you should get from your retailer of choice, and what are the limitations of any specific type? Or, perhaps, you’d like to know – why is it that a strip with a certain LED controller is suspiciously cheap or expensive? You’re more than welcome to, at least, scroll through and fill into any of your addressable LED knowledge gaps, whether it’s voltage drops, color accuracy differences, data transfer protocol basics or dead LED failsafes.

Addressable LEDs have a special place in our hearts, it’s as if the sun started shining brighter after we’ve discovered them… or, perhaps, it’s all the LEDs we are now able to use. WS2812 is a staple of the addressable LED world, which is why we see them even be targets of both clone manufacturers and patent trolls. However, just like the blog post we highlight today mentions, there’s plenty of other options. Either way do keep coming cover a new addressable LED-related hack, like rewriting their drivers to optimize them, or adding 3.3V compatibility with just a diode.

We thank [Helge] for sharing this with us!