Changing Color Under Pressure

When you saw the picture for this article, did you think of a peacock’s feather? These fibers are not harvested from birds, and in fact, the colors come from transparent rubber. As with peacock feathers, they come from the way light reflects off layers of differing materials, this is known as optical interference, and it is the same effect seen on oil slicks. The benefit to using transparent rubber is that the final product is flexible and when drawn, the interference shifts. In short, they change color when stretched.

Most of the sensors we see and feature are electromechanical, which has the drawback that we cannot read them without some form of interface. Something like a microcontroller, gauge, or a slew of 555 timers. Reading a single strain gauge on a torque wrench is not too tricky, but simultaneously reading a dozen gauges spread across a more complex machine such as a quadcopter will probably require graphing software to generate a heat map. With this innovation it could now be done with an on-board camera in real-time. Couple that with machine learning and perhaps you could launch Skynet. Or build a better copter.

The current proof-of-concept weaves the fibers into next-generation bandages to give an intuitive sense of how tightly a dressing should be applied. For the average first-aid responder, the rule is being able to slide a finger between the fabric and skin. That’s an easy indicator, but it only works after the fact whereas saying that the dressing should be orange while wrapping gives constant feedback.

Smart Citizen Opens Eyes and Ears in Barcelona

More often than not, our coverage of projects here at Hackaday tends to be one-off sort of thing. We find something interesting, write it up for our beloved readers, and keep it moving. There’s an unending world of hacks and creations out there, and not a lot of time to cover them all. Still, it’s nice when we occasionally see a project we’ve previously covered “out in the wild” so to speak. A reminder that, while a project’s time on the Hackaday front page might be fleeting, their journey is far from finished.

A perfect example can be found in a recent article posted by the BBC about the battle with noise in Barcelona’s Plaza del Sol. The Plaza is a popular meeting place for tourists and residents alike, with loud parties continuing into the middle of the night, those with homes overlooking the Plaza were struggling to sleep. But to get any changes made, they needed a way to prove to the city council that the noise was beyond reasonable levels.

Enter the Smart Citizen, an open source Arduino-compatible sensor platform developed by Fab Lab Barcelona. We originally covered the Smart Citizen board back in 2013, right after it ran a successful funding campaign on Kickstarter. Armed with the data collected by Smart Citizen sensors deployed around the Plaza, the council has enacted measures to try to quiet things down before midnight.

Today people tend to approach crowdfunded projects with a healthy dose of apprehension, so it’s nice to see validation that they aren’t all flash in the pan ideas. Some of them really do end up making a positive impact, years after the campaign ends.

Of course, we can’t talk about distributed environmental monitoring without mentioning the fantastic work of [Radu Motisan], who’s made it his mission to put advanced sensors in the hands of citizen scientists.

[Thanks to muA for the tip.]

Monitoring Air Quality, One Sleepy Meeting At A Time

To those of us in the corporate world, the conference room is where hope goes to die. Crammed into a space too small for the number of invitees, the room soon glows with radiated body heat and the aromas of humans as the time from their last shower gradually increases. To say it’s not a recipe for productivity is an understatement at best.

Having suffered through too many of these soporific situations, [Charles Ouweland] took matters into his own hands and built this portable air quality meter for meetings. With an OLED display on top and sensors inside, it displays not only the temperature, humidity, and barometric pressure, but also the CO₂ concentration and the levels of volatile organic compounds (VOC), noxious substances sometimes off-gassed from building materials, furniture upholstery, and coworkers alike.

The monitor quantifies his meeting misery, which we’re sure wins him points with his colleagues. For our part, though, what we find interesting is his design process. He started where many of us would, with an Arduino Uno. The sensor modules, a CCS811 for VOC and CO₂ as well as a BME280 for temperature, humidity, and pressure, both needed 3.3 volts, so he added a regulator to knock the Arduino’s 5-volt supply into range and some MOSFETs for level matching. Things were getting bulky, though, so he set about reducing the component count. The Uno went by stripping out its already programmed MCU. That killed the need for the regulator and MOSFETs, since everything would be happy with 3.3 volts. A few more rounds of optimization led to the final product, compact enough to run on a pair of AA batteries.

This is a great lesson in going from prototype to product. And it’s so compact, it could even ride on top of a Roomba to map the conference room’s floor-level air quality.

Tiny $25 Spectrometer Aims to Identify Materials with Ease

Reflectance spectrometers work on a simple principle: different things reflect different wavelengths in different amounts, and because similar materials do this similarly, the measurements can be used as a kind of fingerprint or signature. By measuring how much of which wavelengths get absorbed or reflected by a thing and comparing to other signatures, it’s possible to identify what that thing is made of. This process depends heavily on how accurately measurements can be made, so the sensors are an important part.

[Kris Winer] aims to make this happen with the Compact, $25 Spectrometer entry for The 2018 Hackaday Prize. The project takes advantage of smaller and smarter spectral sensors to fit the essential bits onto a PCB that’s less than an inch square. If the sensors do the job as expected then that’s a big part of the functionality of a reflectance spectrometer contained in a PCB less than an inch square and under $25; definitely a feat we’re happy to see.

Headlight Mod For An Audi A3

If you have a car that is getting on in years, it may be missing some of the latest frills and features that the latest models sport. [Muris] has a slightly dated Audi A3 8P which did not have an AUTO setting for the headlights. In the newer models, this feature turns on the headlights when the ambient light falls below a threshold level (overcast conditions or when going through a tunnel), or when the windshield wipers are turned on. The light sensor is integrated behind the rear view mirror in a special mount, requiring an expensive windshield upgrade if he were to opt for the factory retrofit. Instead, he decided to build his own Automatic Headlights Sensor upgrade for his Audi A3.

His local regulations require the car headlights to be on all the time when the vehicle is in motion. So adding this feature may seem moot at first sight. But [Muris] programmed the headlights to be powered at 70% during daytime conditions and switch to 100% when his sensor detects low ambient light conditions. In the power save mode, all of the other non-essential lights (number plate, tail light) are also turned off to hopefully extend their life. He achieved this by using the VCDS (VAG-COM Diagnostic System) – a widely used aftermarket diagnostics tool for VW-Audi Group vehicles. His tiny circuit switches the lights between the two power settings.

His plan was to install the device without disturbing the original wiring or light switch assembly in any way. The low-powered device consists of a PIC micro-controller, an LDR (light dependent resistor) for light sensing and a low current relay which switches between the two modes. Setting the threshold at which the circuit switches the output is adjusted by a variable trimpot acting as a voltage divider with the LDR. [Muris] wired up a short custom harness which let him install this circuit between the default light switch and the car electronics. After switching on power, he has 15 seconds to enable or disable his unit by toggling the light switch five times, and that status gets stored in memory. The tiny board is assembled using SMD parts and is protected with a heatshrink sleeve. The circuit would work equally well with a lot of other cars, so If you’ve got one which could do with this feature upgrade, then [Muris] has the Eagle CAD files and code available for download on his blog.

Check out the video below where he runs a demo, describes his circuit in detail and then proceeds to assemble the PCB without using a vise or a third hand to hold the PCB. That’s a fancy watch he’s sporting at 00:50 s down the video.

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Open Source Underwater Distributed Sensor Network

One way to design an underwater monitoring device is to take inspiration from nature and emulate an underwater creature. [Michael Barton-Sweeney] is making devices in the shape of, and functioning somewhat like, clams for his open source underwater distributed sensor network.

Underwater distributed sensor network descent and ascentThe clams contain the electronics, sensors, and means of descending and ascending within their shells. A bunch of them are dropped overboard on the surface. Their shells open, allowing the gas within to escape and they sink. As they descend they sample the water. When they reach the bottom, gas fills a bladder and they ascend back to the surface with their data where they’re collected in a net.

Thus far he’s made a few clams using acrylic for the shells which he’s blown himself. He soldered the electronics together free-form and gave them a conformal coating of epoxy. He’s also used a thermistor as a stand-in for other sensors and is already working on a saturometer, used for measuring the total dissolved gas (TDG) in the water. Knowing the TDG is useful for understanding and mitigating supersaturation of water which can lead to fish kills.

He’s also given a lot of thought into the materials used since some clams may not make it back up and would have to degrade or be benign where they rest. For example, he’s been using a lithium battery for now but would like to use copper on one shell and zinc on another to make a salt water battery, if he can make it produce enough power. He’s also considering using 3D printing since PLA is biodegradable. However, straight PLA could be subject to fouling by underwater organisms and would require cleaning, which would be time-consuming. PLA becomes soft when heated in a dishwasher and so he’s been looking into a PLA and calcium carbonate filament instead.

Check out his hackaday.io page where he talks about all these and more issues and feel free to make any suggestions.

Robot Radar Module

For his Hackaday Prize entry, [Ted Yapo] is building a Robot Radar Module breakout board. His design uses the A111 60 GHz pulsed coherent radar (PCR) sensor from Acconeer AB (New Part alert!) .

The A111 is a low power, high precision sensor ideal for use in object detection or gesture sensing applications. The BGA package is tiny – 5.5 mm x 5.2 mm, but it does not appear very difficult for a hacker to assemble. The sensor includes an integrated baseband, RF front-end and Antenna in Package so you don’t have to mess with RF layout headaches. Acconeer claims the sensor performance is not affected with interference from noise, dust, color and direct or indirect light. Sensing range is about 2 m with a +/- 2 mm accuracy. And at just under $10 a pop for 10 units or more, it would make a nice addition to augment the sensor package on a Robot.

To get started, [Ted] is keeping his design simple and small – the break out board measures just 32 mm x 32 mm. The radar sensor itself doesn’t require any parts other than a crystal and its loading capacitors. A LDO takes care of the 1.8 V required by the A111. Three 74LVC2T45 chips translate the SPI digital interface from 1.8 V to external logic levels between 1.8 V to 5 V. The three level translation chips could possible be replaced by a single six or eight channel translator – such as one from the TXB series from TI. For his first PCB iteration, [Ted] is expecting to run in to some layout or performance issues, so if you have any feedback to give him on his design, check out his hardware repository on Github.

Acconeer provides a Getting Started guide for their Evaluation Kits, which includes a detailed Raspberry-Pi / Raspbian installation and an accompanying video (embedded after the break) targeted at hackers. We are eagerly looking forward to the progress that [Ted] makes with this sensor breakout. Combined with LiDAR ToF sensor breakout boards, such as the MappyDot, it would be a great addition to your robot’s sensing capabilities.

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