Low Noise Floor Microphone

[Matt] likes to make videos (and he’s pretty good at it judging by the quality of his videos). But video isn’t much without audio. Handheld recorders with small built-in microphones have a fairly high noise floor so [Matt] has a Rode NT1-A — a pricey but very quiet microphone. However, for field work, it isn’t handy since it requires a power supply and preamp to go along with it.

low-noise-floor-binaural-microphoneAnother problem is that for stereo recording you need two and because they are quiet, they tend to pick up handling noise so you probably need to mount them on tripods. That’s all too much to carry around, especially on a hike. So [Matt] cannibalized two microphones. He repackaged them in a shock mount (made from a bird feeder and elastic), and added a battery pack and a custom preamp. The shock mount eliminates the handling noise and the custom PC boards mean you don’t have to carry a lot of extra gear.

The end result (see the video below) looks like someone made a purse out of a tribble, but it does sound good. If you hang on through most of the video (of fast forward to about 7:25), you can hear the microphones picking up thunderstorms, the ocean, the wind, and even [Matt’s] heartbeat.

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Filtering Noisy Data with an Arduino

One of the first frustrating situations a beginning microcontroller programmer will come across is the issue of debouncing switches. Microcontrollers are faster than switches, and the switch has yet to be built that can change state in zero time like they can on paper. This hurdle is easily overcome, but soon we are all faced with another issue: filtering noise from an analog signal. Luckily [Paul Martinsen] has put together a primer of three different ways to use an Arduino to filter signals.

The first (and fastest, simplest, etc.) way to filter an analog signal is to sample a bunch of times and then average all of the samples together. This will eliminate most outliers and chatter without losing much of the information. From there, the tutorial moves on to programming a running average to help increase the sample time (but consume much more memory). Finally, [Paul] takes a look at exponential filters, which are recursive, use less memory, and can be tweaked to respond to changes in different ways.

[Paul] discusses all of the perks and downsides of each method and provides examples for each as well. It’s worth checking out, whether you’re a seasoned veteran who might glean some nuance or you’re a beginner who hasn’t even encountered this problem yet. And if you’re still working on debouncing a digital input, we have you covered there, too.

Hackaday Prize Entry: Real Life XEyes

There’s a lot of tech that goes into animatronics, cosplay, and costumes. For their Hackaday Prize entry, [Dasaki] and [Dylan] are taking the eyes in a costume or Halloween prop to the next level with animatronic eyes that look where the wearer of this crazy confabulation is looking. It’s XEyes in real life, and it promises to be a part of some very, very cool costumes.

The mechanics of this system are actually pretty simple — it’s just a few servos joined together to make a pair of robotic eyes move up and down, and left to right. This entire mechanism is mounted on a frame, to which is attached a very small camera pointed directly at the user’s (real) eye. The software is where things get fun. That’s a basic eye-tracking setup, with IR light illuminating the pupil, and a compute unit that can calculate where the user is looking.

For the software, [Dasaki] and [Dylan] have collected a bunch of links, but right now the best solutions are the OpenMV and the Eye of Horus project from last year’s Hackaday Prize. It’s a great project, and a really fun entry for the Automation portion of this year’s Hackaday Prize.

Weather-aware Shoe Rack Helps You Get Ready for the Day

If you’re anything like us, your complete shoe collection consists of a pair of work boots and a pair of ratty sneakers that need to wait until the next household haz-mat day to be retired. But some people have a thing for shoes, and knowing which pair is suitable for the weather on any given day is such a bother. And that’s the rationale behind this Raspberry Pi-driven weather-enabled shoe rack.

The rack itself is [zealen]’s first woodworking project, and for a serious shoeaholic it’s probably too small by an order of magnitude. But for proof of principle it does just fine. The rack holds six pairs, each with an LED to light it up. A PIR sensor on the top triggers the Raspberry Pi to light up a particular pair based on the weather, which we assume is scraped off the web somehow. [zealen] admits that the fit and finish leave a bit to be desired, but for a first Rasp Pi project, it’s pretty accomplished. There’s plenty of room for improvement, of course – RFID tags in the shoes to allow them to be placed anywhere in the rack springs to mind.

[via r/raspberry_pi]

Working in Peace With an Off-Grid Office Shed

Finding a good work space at home isn’t a trivial task, especially when you’ve got a wife and kid. A lot of us use a spare bedroom, basement, or garage as a space to work on our hobbies (or jobs). But, the lack of true separation from the home can make getting real work done difficult. For many of us, we need to have the mental distance between our living space and our working space in order to actually get stuff done.

This is the problem [Syonyk] had — he needed a quiet place to work that was separated from the rest of his house. To accomplish this, he used a Tuff Shed and set it up to run off-grid. The reason for going off-grid wasn’t purely environmental, it was actually more practical than trying to run power lines from the house. Because of the geology where he lives, burying power lines wasn’t financially feasible.

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Amazing Carbon Foam Doesn’t Take Much Bread

A lot of people knew the Space Shuttle had ceramic tiles to protect its nose from reentry heat. That’s mostly because the tiles fell off a lot and each one was a unique shape, so it got a lot of press coverage. However, you didn’t hear as much about the parts of the orbiter that got really hot: the forward part of the wings and the tip of the nose. For those, NASA used an exotic material called RCC or reinforced carbon-carbon. Other uses include missile nose cones and Formula One brakes. A similar material, carbon fiber-reinforced silicon carbide appears in some high-end car brakes. These materials can take high temperatures, easily.

[AvE] wanted to make some carbon foam for experiments. It does take a little bread, though. Not money, but literal bread. To create the foam, he burns bread slices in a chamber full of argon. The stuff has some amazing properties.

In the video below, you can see the foam protecting a thermocouple from a torch flame and even holding melting aluminum. Not bad for a few pieces of bread.

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Hacklet 122 – Spectrometers

There is always something interesting to find when browsing the projects on Hackaday.io. I’m always amazed at how much hackers can get done in their basements and home labs. One surprising trend I’ve found is the sheer number of spectrometer projects people across the globe are working on. I’ve always known what a spectrometer is, but I never knew so many hackers would want them. The numbers don’t lie though – plenty of hackers around the world want to measure the spectra of light — be it to test out a new LED, or determine the structure of an object. This week we’re checking out some of the best spectrometer projects on Hackaday.io!

ramanpiWe start with [fl@C@] and ramanPi – Raman Spectrometer. RamanPi is one of the first spectrometer projects on Hackaday.io. [fl@C@] entered his project in the 2014 Hackaday Prize, and was one of 5 finalists. As the name implies, ramanPi is a raman spectrometer, a type often used in chemistry. [fl@C@’s] original use for the machine was determining atomic bond angles. RamanPi uses 3D printed parts created with standard desktop printers wherever possible. A Raspberry Pi runs the system, originally a model B, though now I’m sure a Pi 3 would fit the bill. The detector is a Toshiba linear CCD.


dh-specNext up is [David H Haffner Sr] with DH 4.0 Spectrometer V 4 ( upgrade 2 ). [David’s] project doesn’t give a lot of background in the description text – he dives right in to the technical details of designing and building a spectrometer. His sensor is a JDEPC-OV04, which is a webcam module intended for use in laptops. Much of [David’s] recent work has been on the optical path. Optical spectrometers can use a diffraction grating and a slit to split light into spectra. [David] is using a recordable DVD as his diffraction grating. The slit is a bit more home-made. Two Gillette razor blades and an acetate strip are used to form an optical slit only 0.11 mm wide. [David] has already used his spectrometer to analyze crude oil.

pure-engNext we have [Pure Engineering] with C12666MA Micro-Spectrometer. Electro-Optics manufacturer Hamamatsu has created an optical spectrometer in a fingertip sized can. Their C12666MA micro-spectrometer sounds like it must be magic — and it is. The magic of Microelectromechanical systems (MEMS) have brought this device to life. Bringing one of these devices up isn’t exactly an easy task though. [Pure Engineering] has designed a breakout board for the C12666MA. They’ve even included a 404nm laser diode and a white LED for illumination. The board can plug into a standard Arduino header.

adamFinally, we have [Adam] with Handheld VNIR Spectrometer. VNIR in this case stands for visible and near-infrared. [Adam] created this device so he could learn how spectrometers worked. That’s a noble purpose if I ever heard one. He is building his system to be portable, so he can take measurements outside the lab. The sensor is a Sony ILX511B linear CCD. An Arduino nano reads the CCD and passes the data on to a PC for analysis. [Adam’s] diffraction grating is a concave holographic affair from Public Lab. [Adam] is also using an acetate slit purchased from Public Lab. Illumination enters via a fiber optic bundle.

If you want to see more spectrometer projects, check out our new spectrometer projects list. See a project I might have missed? Don’t be shy, just drop me a message on Hackaday.io. That’s it for this week’s Hacklet, As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!