Capacitive And Resistive Touch Sensors For Wearables

March 17, 2018 by Brian Benchoff 5 Comments

When you look at switching solutions for electronic wearables, your options are limited. With a clever application of conductive fabric and thread, you can cobble together a simple switch, but the vast array of switch solutions is much more than that. This one is different. The zPatch from [Paul Strohmeier], [Jarrod Knibbe], [Sebastian Boring], and [Kasper Hornæk] at the Human-Centred Computing Section at the University of Copenhagen gives eTextiles capacitive and resistive input. It’s a force sensor, a pressure sensor, and a switch, all made completely out of fabric.

The design of this fabric touch sensor is based around a non-woven resistive fabric made by Eeonyx. This fabric is piezo-resistive when compressed. This material is sandwiched between two layers of silver-plated polyamide fabric, which is then connected to the analog input of a microcontroller. On top of all this is a polyester mesh, with everything held together with iron-on sheets.

Reading this sensor with a microcontroller is extremely similar to a capacitive touch sensor made out of copper and FR4. All the code is available in a repo, and all the materials to reproduce this work can be found in the various links provided by the team. That last point — reproducibility — is huge for an academic work. Not only did the team manage to come up with something interesting, they actually provided enough documentation to reproduce their build.

In the video below, you can see how this sensor can be used to sense a hand hovering, a light touch, a hard press, or anything in between. Only two analog pins are required for each sensor, making the routing and layout of this eTextile should be relatively easy to integrate into clothing. It’s a great build, and we can’t wait to see the community pick up on these really cool sensors.

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Print, Rinse, Wear. Nanowire Circuits For Your Microfibre Clothing.

March 11, 2018 by James Hobson 7 Comments

While our bodies are pretty amazing, their dynamic nature makes integrating circuits into our clothing a frustrating process. Squaring up against this challenge, a team of researchers from North Carolina State University have hit upon a potential boon for wearable electronics: silver nanowires capable of being printed on flexible, stretchy substrates.

It helps that the properties of silver nanowires lend themselves to the needs of wearable circuits — flexible and springy in their own right — but are not without complications. Silver nanowires tend to clog print nozzles during printing, so the research team enlarged the nozzle and suspended the nanowires in a water-soluble solvent, dramatically cutting the chance of clogging. Normally this would have a negative impact on precision, but the team employed electrostatic force to draw the ink to the desired location and maintain print resolution. Once printed, the solvent is rinsed away and the wearable circuit is ready for use.

By controlling print parameters — such as ink viscosity and concentration — the team are able to print on a wide variety of materials. Successful prototypes thus far include a glove with an integrated heating circuit and an electrocardiograph electrode, but otherwise the size of the printer is the only factor limiting the scale of the print. Until this technique becomes more widely available, interested parties might have to put their stock into more homebrew methods.

[Thanks for the tip, Qes!]

Wireless Protocol Reverse Engineered To Create Wrist Wearable Mouse

March 10, 2018 by Dan Maloney 7 Comments

We’ve seen a few near-future sci-fi films recently where computers respond not just to touchscreen gestures but also to broad commands, like swiping a phone to throw its display onto a large flat panel display. It’s a nice metaphor, and if we’re going to see something like it soon, perhaps this wrist-mounted pointing device will be one way to get there.

The video below shows the finished product in action, with the cursor controlled by arm movements. Finger gestures that are very much like handling a real mouse’s buttons are interpreted as clicks. The wearable has a Nano, an MPU6050 IMU, and a nRF24L01 transceiver, all powered by some coin cells and tucked nicely into a 3D-printed case. To be honest, as cool as [Ronan Gaillard]’s wrist mouse is, the real story here is the reverse engineering he and his classmate did to pull this one off.

The road to the finished product was very interesting and more detail is shared in their final presentation (in French and heavy with memes). Our French is sufficient only to decipher “Le dongle Logitech,” but there are enough packet diagrams supporting into get the gist. They sniffed the packets going between a wireless keyboard and its dongle and figured out how to imitate mouse movements using an NRF24 module. Translating wrist and finger movements to cursor position via the 6-axis IMU involved some fairly fancy math, but it all seems to have worked in the end, and it makes for a very impressive project.

Is sniffing wireless packets in your future? Perhaps this guide to Wireshark and the nRF24L01 will prove useful.

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Membership Ring Of The Electronic Illuminati

February 10, 2018 by Mike Szczys 21 Comments

When the cabal of electronic design gurus that pull the invisible strings of the hardware world get together, we imagine they have to show this ring to prove their identity. This is the work of [Zach Fredin], and you’re going to be shocked by the construction and execution of what he calls Cyborg Ring.

The most obvious feature of the Cyborg Ring is the collection of addressable LEDs that occupy the area where gems would be found on a ring. What might not be so obvious is that this is constructed completely of electronic components, and doesn’t use any traditional mechanical parts like standoffs. Quite literally, the surface mount devices are structural in this ring.

They are also electrical. Here you can see a detail of how [Zach] pulled this off. We are looking at the underside of the ring, the part that goes below your knuckle. One of the two PCBs that are sized to fit your finger has been placed in a Stick Vise while the QFN processor is soldered on end, and the pairs of SMD resistors are put in place.

The precise measurements of each part make it possible to choose components that will perfectly span the gap between the two boards. In the background of the image you can see SMD resistors on their long ends — a technique he used to allow the LEDs themselves to span between one resistor on each of the two PDBs to complete the circuit. Incredible, right?

But it gets better. [Zach] ended up with a working prototype, but has continued to forge ahead with new design iterations. These updates are a delight to read! Make sure you follow his project and check in regularly; if you’ve already looked at this now’s the time to go back and see the new work. The gold pads for the minuscule coin cells which power the ring are being reselected as the batteries didn’t fit well on the original. Some layout problems are being tweaked. And the new spin of boards should be back from fab in a week or so.

Don’t miss the demo video found below. We really like seeing projects that build within the wearble ring form factor. It’s an impressive constraint which [Zach] seems to have mastered. Another favorite of ours is [Kevin’s] Arduboy ring.

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Beating Life-Force Amulet

February 4, 2018 by James Hobson 17 Comments

It’s one thing to see science-fiction slowly become reality, but quite another to take that process into your own hands. Inspired by a movie prop, [Eric Strebel] decided to build himself a 21st science-fiction artifact: a pulsing, life-force amulet.

At the — aheam — heart of this amulet is a blinking LED circuit which [Strebel] modified into a slow pulse with the help of his friends. To add to the surreal quality of the amulet, he sourced a stone from a local gem show, bringing his circuit along to get an idea of what the final product would look like. Once [Strebel] had shaped the stone to a more manageable size, he took a polyester filler mold of its rear face to use as a base from which to cast a durable resin housing for the circuit.

[Strebel] is using a pair of coin cell batteries which fit snugly behind the glowing LED, and in case he ever needs to get inside the amulet, he’s attached the stone to the rear with sew-on straps — super-gluing them to each piece. He went for a bit of an industrial look for the necklace — a braided oil line with a modified quick-release clasp that works like a charm.

How does this amulet stack up to one from the 23rd century? You be the judge!

Be The Electronic Chameleon

January 30, 2018 by Al Williams 4 Comments

If you want to work with wearables, you have to pay a little more attention to color. It is one thing to have a 3D printer board colored green or purple with lots of different color components onboard. But if it is something people will wear, they are going to be more choosy. [Sdekon] shows us his technique of using Leuco dye to create items that change color electrically. Well, technically, the dye is heat-sensitive, but it is easy to convert electricity to heat. You can see the final result in the video, below.

The electronics here isn’t a big deal — just some nichrome wire. But the textile art processes are well worth a read. Using a piece of pantyhose as a silk screen, he uses ModPodge to mask the screen. Then he weaves nichrome wire with regular yarn to create a heatable fabric. Don’t have a loom for weaving? No problem. Just make one out of cardboard. There’s even a technique called couching, so there’s lots of variety in the textile arts used to create the project.

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Weaving With Light: An OLED Fibre Fabric Display

January 21, 2018 by Jenny List 11 Comments

If you think of wearable electronic projects, in many cases what may come to mind are the use of addressable LEDs, perhaps on strips or on sewable PCBs like the Neopixel and similar products. They make an attractive twinkling fashion show, but there remains a feeling that in many cases once you have seen one project, you have seen them all.

So if you are tiring of static sewable LED projects and would like to look forward to something altogether more exciting, take a look at some bleeding-edge research from a team at KAIST, the Korean Advanced Institute of Science & Technology. They have created OLED fibres and woven them into fabric in a way that appears such that they can be lit at individual points to create addressable pixels. In this way there is potential for fabrics that incorporate entire LED displays within their construction rather than in which they serve as a substrate.

The especially interesting feature of the OLED fibres from the KAIST team is that their process does not require any high temperatures, meaning that a whole range of everyday textile fibres can be used as substrates for OLEDs. The results are durable and do not lose OLED performance under tension, meaning that there is the possibility of their becoming practical fabrics for use in garments.

While this technology is a little way away from a piece of clothing you might buy from a store, the fact that it does not rely on special processes during weaving means that when the fibres become commercially available we are likely to see their speedy adoption. Meanwhile you can buy conductive fabric, but you might have to take a multimeter to the store to find it.

Via EENewsLED, and thank you [Carl] for the tip.