An Open Source Detector For Identifying Plastics

December 13, 2021 by Tom Nardi 18 Comments

One of the challenges involved in recycling plastic is determining the specific type of plastic a given item is actually made of. To keep up with demand, large scale recycling centers rely on various automated systems to separate different types of plastic from a stream of incoming material. But in less technologically advanced parts of the world, workers can find themselves having to manually identify plastic objects; a time consuming and error-prone process.

To try and improve on the situation, [Jerry de Vos], [Armin Straller], and [Jure Vidmar] have been working on a handheld open hardware device that they refer to simply enough as the Plastic Scanner. The hope is that their pocket-sized unit could be used in the field to positively identify various types of plastic by measuring its reflectivity to infrared light. The device promises to be very easy to operate, as users simply need to bring the device close to a piece of plastic, push the button, and wait for the information to pop up on the OLED display.

Or at least, that’s the idea. While the team eventually hopes to release a kit to build your own handheld Plastic Scanner, it seems that the hardware isn’t quite ready for production. The most recent work appears to have been put in, not unexpectedly, the development board that lets the team refine their process. The development unit combines an array of IR LEDs with wavelengths ranging from 850 to 1650 nanometers, a InGaAs photodiode connected to an ADS1256 24-bit analog-to-digital converter (ADC), and an Arduino Uno. In comparison, the final hardware uses a Raspberry Pi Zero and a smaller “breakout board” that contains the sensor and IR LEDs.

Browsing through the software repository for the project, we can see the device uses Python, TensorFlow Lite, and a database of IR reflectivity values for known plastics to try and determine the closest match. Obviously the accuracy of such a system is going to be highly dependent on the quantity of known-good data, but at least for now, it appears the user is responsible for building up their own collection or IR values.

As interesting as this project is, we’re a bit skeptical about its purely optical approach to identifying plastics. Automated recycling centers do use infrared spectroscopy, but it’s only one tool of many that are employed. Without additional data points, such as the density or electrostatic properties of the plastic being tested, it seems like the Plastic Scanner would have a fairly high margin of error. Just taking into account the wide array of textures and colors the user is likely to encounter while using the device will be a considerable challenge.

Continue reading “An Open Source Detector For Identifying Plastics” →

This is a MIDI harp that is played by waving your hands in the air over the infrared distance sensors.

Teensy MIDI Air Harp Sounds Huge

November 15, 2021 by Kristina Panos 4 Comments

Some of the coolest sounds come from wild instruments like orchestra strings, fretless basses, and theremins — instruments that aren’t tied down by the constraints of frets and other kinds of note boundaries. [XenonJohn]’s air harp is definitely among this class of music makers, all of which require a certain level of manual finesse to play well.

Although inspired by Jean-Michel Jarre’s laser harp, there are no lasers here. This is a MIDI aetherharp, aka an air harp, and it is played by interrupting the signals from a set of eight infrared distance sensors. These sensors can be played at three different heights for a total of 24 notes, plus there’s a little joystick for doing pitch bends.

Inside the wooden enclosure of this aetherharp is a Teensy 3.5 and eight infrared distance sensors with particularly long ranges. On top is a layer of red acrylic that doesn’t affect the playability, except in bright sunlight. Although you could use most any MIDI software to produce the actual sounds, [XenonJohn] chose VMPK (Virtual MIDI Piano Keyboard). Be sure to check it out in action after the break.

Not dangerous enough for you? Here’s a laser harp that involves a Tesla coil.

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Speaker ‘Stun Gun’ Aims To Combat China’s Dancing Grannies

October 28, 2021 by Lewin Day 74 Comments

One of the more popular social activities in China is group dancing in public squares. Often the pastime of many middle-aged and older women, participants are colloquially referred to as “dancing grannies.” While the activity is relatively wholesome, some dancers have begun to draw the ire of their neighbourhoods with their loud music and attempts to dominate the use of public parks and recreational areas.

Naturally, a technological solution sprung up promising to solve the problem. The South China Morning Post has reported on a “stun gun” device which claims to neutralise speakers from a distance, in an effort to shut down dance gatherings. The device created a huge stir on social media, as well as many questions about how it could work. It’s simpler, and a bit less cool, than you think. Continue reading “Speaker ‘Stun Gun’ Aims To Combat China’s Dancing Grannies” →

How Much Is That Shirt In The (Atmospheric) Window?

October 26, 2021 by Kristina Panos 41 Comments

Summer is fading into a memory now, but as surely as the earth orbits the sun, those hot and sweaty days will return soon enough. And what can you do about it at the level of a single, suffering human being? After all, a person can only remove so much clothing to help cool off. Until someone figures out a way to make those stillsuits from Dune, we need an interim solution in which to drape ourselves.

We’ve seen the whitest paint possible for cooling buildings, and then we saw a newer, whiter and more award-winning paint a few months later. This paint works by the principle of passive cooling. Because of its color and composition, it reflects most light and absorbs some heat, which gets radiated away into the mid-infrared spectrum. It does this by slipping out Earth’s atmospheric window and into space. Now, a team based in China have applied the passive cooling principle to fabric. Continue reading “How Much Is That Shirt In The (Atmospheric) Window?” →

World’s Cheapest And Possibly Worst IR Camera

October 7, 2021 by Al Williams 16 Comments

Don’t blame us for the title. [CCrome] admits it may well be the cheapest and worst IR camera available. The concept is surprisingly simple. Mount a cheap Harbor Freight non-contact thermometer on a 3D printer carriage and use it to scan the target. The design files are available on GitHub.

There is, of course, an Arduino to grab the data and send it to the PC. Some Python code takes care of converting it into an image.

Perhaps you don’t need a camera, but having a way to communicate with an $11 IR temperature sensor might come in handy someday. You do have to mash the measurement button down, so [CCrome] used the 3D printer to make a clamp for the button that also holds the POGO pins to the PCB. We would have been tempted to solder across the switch and also solder the wires to the pad. But, then again, you need a 3D printer for the project anyway.

Don’t expect the results you would get from a real thermal sensor. If you want that, you may have to build it yourself or open your wallet wide. If you need some inspiration for a use case, look at the thermal camera contest from a few years back.

Is Your Movie Too Loud? Can’t Hear The Dialogue? This Circuit Can Help.

September 29, 2021 by Jim Heaney 67 Comments

Everyone loves watching movies, that is, so long as you can hear what the characters on screen are saying. [GreatScott] found this second part difficult while watching through BladeRunner 2049, so he designed an automatic volume adjuster to assist.

At a high level, the solution is fairly straightforward; when there is loud music playing in a movie, turn the volume down. The challenge is how to actually achieve that. The first step was controlling the volume. To avoid having to modify or damage his sound system, [GreatScott] opted instead to mimic the volume up and down signals of his remote over IR. Using the very handy IRremote library for Arduino and its built-in decoding functionality, he was able to identify and replicate the signals with his own IR LED.

The second step in this process was measuring the volume of the movie. [GreatScott] achieved this with a microphone and amplifier circuit, that was then piped into one of the analog pins of the Arduino Pro Micro at the heart of the build. Since the audio being sampled could have a frequency as high as 20 kHz, the ADC Prescaler had to be adjusted from its standard value, which would have only permitted measurements at less than 5 kHz.

The third step was writing the algorithm to detect loud music and adjust the volume accordingly. The Arduino will measure the audio until a sound greater than the dead band value, set with one of the two onboard potentiometers, is detected. This then triggers the Arduino to start a timer, to see how frequently the upper limit is being surpassed. If it is just one or two occasionally loud noises (like a scream, a clap, whistling, etc.) the Arduino will not take any action, but multiple loud noises in rapid succession will then trigger the volume down command over the IR LED. A second potentiometer allows for adjustment of this timer’s critical value, so that you can make the system respond faster or slower depending on the movie.

Once the sound has been detected to have dropped down below a critical vaue, the Arduino assumes that the movie is back to dialog and will increase the volume by the number of times it decreased it before, leaving you back at the perfect volume.

Maybe you’re the type that cares more for the visuals of a movie, rather than the audio. In that case, this e-paper movie display will be perfect for giving you time to appreciate every frame!

Continue reading “Is Your Movie Too Loud? Can’t Hear The Dialogue? This Circuit Can Help.” →

An OSHW IR Remote Control Powered By The ATtiny13A

July 2, 2021 by Tom Nardi 15 Comments

The new hotness in consumer electronics might be RF remotes based on protocols like Bluetooth Low Energy, but there’s still plenty of life left in the classic infrared remote. Especially with projects like TinyRemoteXL from [Stefan Wagner], which let you build and program an IR “clicker” of your own. Whether you want to spin up your own custom universal remote or create a beefed up version of the TV-B-Gone, this open source effort is a great place to start.

As you might have guessed from the name, this project is actually a larger version of the TinyRemote that [Stefan] put together previously. The documentation for that project goes a bit more into the nuts and bolts of talking IR, and is definitely worth a read if you’re into the low level stuff. For the original five button TinyRemote, the hardware consists of little more than a ATtiny13A microcontroller, a pair of IR LEDs, and the transistors to drive them.

But on the XL, things are a bit trickier as there are now twelve buttons for the ATtiny13A to read. Obviously there aren’t enough pins to read so many buttons directly, but with a combination of BAS16TW diode arrays and resistors, [Stefan] is able to detect what button was pressed using the chip’s interrupt pin and ADC. Certainly a handy trick to have in the back of your mind, and the open source nature of this project gives you a great chance to see how it’s implemented.

Between this project and the impressive development board [Djordje Mandic] released recently, it seems we’re looking at something of an infrared hacking revival. Earlier this year we even saw the commercial release of an IR-equipped ESP8266 board.