Get To Know Touch With This Dev Board

December 31, 2022 by Jenny List 5 Comments

In the catalogue of the Chinese parts supplier LCSC can be found many parts not available from American or European suppliers, and thus anyone who wants to evaluate them can find themselves at a disadvantage. [Sleepy Pony Labs] had just such a part catch their eye, the Sam&Wing AI08 8 channel capacitive touch controller. How to evaluate a chip with little information? Design a dev board, of course!

The chip tested is part of a family all providing similar functionality, but with a variety of interface options. The part tested has eight touch inputs and a BCD output. Said output is used to feed a 74 series decoder chip and drive some LEDs. The touch pads were designed with reference to a Microchip application note which incidentally makes for fascinating reading on the subject as it covers far more than just simple touch buttons.

Whether or not you’ll need this touch chip is a matter for your own designs, however, what this project demonstrates is that with the ready availability of cheap custom PCBs and unexpected parts it’s not beyond reason to create boards just for evaluation purposes.

Perhaps the subject of a previous Hackaday piece would have found this board useful.

The assembled switch PCB in the palm of its creator's hand

TTP223 Brings Simple Touch Controls To A LED Lamp

October 4, 2022 by Arya Voronova 7 Comments

You can buy small modules with capacitive touch detection ICs — most often it’s the TTP223, a single-button capacitive model with configurable output modes. These are designed to pair with a microcontroller or some simple logic-level input, but [Alain Mauer] wanted was to bring touch control to a simple LED strip. Not to be set deterred, he’s put together a simple TTP223-based switch board.

Initially, he made a prototype using one of the regular TTP223 boards as a module, but then transferred the full schematic onto a single PCB. The final board uses an NPN transistor capable of handling up to 3 amps to do the switching job, and Zener-based regulation to provide 5 V for the TTP223 itself from the 12 V input. [Alain] shares the schematic, as well as BOM together with Gerber files for a 2×3 panel in case you’re interested in adding a few of these handy boards to your parts bin.

The TTP223 is a ubiquitous and quite capable chip – we’ve seen it used for building a mouse with low actuation force buttons, a soft power switch, and even a UV-sensing talisman that’s equal parts miniature electronics and fascinating metalwork.

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REMOTICON 2021 // Hal Rodriguez And Sahrye Cohen Combine Couture And Circuitry

March 31, 2022 by Kristina Panos 3 Comments

[Hal Rodriguez] and [Sahrye Cohen] of Amped Atelier focus on creating interactive wearable garments with some fairly high standards. Every garment must be pretty, and has to either be controllable by the wearer, through a set of sensors, or even by the audience via Bluetooth. Among their past creations are a dress with color sensors and 3D-printed scales on the front that change color, and a flowing pantsuit designed for a dancer using an accelerometer to make light patterns based on her movements.

Conductive Melody — a wearable musical instrument that is the focus of [Sahrye] and [Hal]’s Remoticon 2021 talk — was created for a presentation at Beakerhead Festival, a multi-day STEAM-based gathering in Calgary. [Sahrye] and [Hal] truly joined forces for this one, because [Sahrye] is all about electronics and costuming, and [Hal] is into synths and electronic music. You can see the demo in the video after the break.

The dress’s form is inspired by classical instruments and the types of clothing that they in turn inspired, such as long, generous sleeves for harp players and pianists. So [Hal] and [Sahrye] dreamed up a dress with a single large playable sleeve that hangs down from the mid- and upper arm. The sleeve is covered with laser-cut conductive fabric curlicues that look like a baroque interpretation of harp strings. Play a note by touching one of these traces, and the lights on the front of the dress will move in sync with the music.

[Sahrye] started the dress portion of Conductive Melody with a sketch of the garment’s broad strokes, then painted a more final drawing with lots of detail. Then she made a muslin, which is kind of the breadboard version of a project in garment-making where thin cotton fabric is used to help visualize the end result. Once satisfied with the fit, [Sahrye] then made the final dress out of good fabric. And we mean really good fabric — silk, in this case. Because as [Sahrye] says, if you’re going to make a one-off, why not make as nicely as possible? We can totally get behind that.

[Sahrye] says she is always thinking about how a wearable will be worn, and how it will be washed or otherwise cared for. That sequined and semi-sheer section of the bodice hides the LEDs and their wiring quite well, while still being comfortable for the wearer.

Inside the sleeve is an MPRP121 capacitive touch sensor and an Arduino that controls the LEDs and sends the signals to a Raspberry Pi hidden among the ruffles in the back of the dress.

The Pi is running Piano Genie, which can turn eight inputs into an 88-key piano in real time. When no one is playing the sleeve, the lights have a standby mode of mellow yellows and whites that fade in and out slowly compared to the more upbeat rainbow of musical mode.

We love to see wearable projects — especially such fancy creations! — but we know how finicky they can be. Among the lessons learned by [Sahrye] and [Hal]: don’t make your conductive fabric traces too thin, and silver conductive materials may tarnish irreparably. We just hope they didn’t have to waste too much conductive fabric or that nice blue silk to find this out.

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Capacitive Touch Controller For FPGAs

October 24, 2021 by Bryan Cockfield 10 Comments

Most projects that interface with the real world need some sort of input device. Obviously this article is being written from a standardized “human interface device” but when the computers become smaller the problem can get more complicated. We can’t hook up a USB keyboard to every microcontroller since we often only need a few buttons, but even buttons can be a little bit too cumbersome for some applications. For something even simpler, we would like to turn your attention to capacitive touch controllers.

Granted, these devices are really only simpler from a hardware perspective. Rather than a switch that can be prone to failure either when its moving parts break or its contacts become corroded, a capacitive touch button only needs a certain conductive area on something like a PCB, along with a few passive components, to work. The real difficulty is in the software, so this project aims to make it simpler to bring these sort of devices to any FPGA that needs some sort of interface like this. It can operate in stand-alone mode or in a custom user interface, and was written to be platform-independent in VHDL without the need for any dependencies or macros.

The project’s page goes into a great amount of detail on how capacitive touch sensors like these work in general, and describes the operation of this specific code as well. Everything is open source, so it’s ready to be put to work right away. If you need capacitive touch capabilities on something like a microcontroller, though, take a look at this tiny Atmel-powered musical instrument instead.

Mice with capactive sensors instead of buttons. Designed for people with low mobility.

Capacitive Mouse Built For A Friend Makes For A Touching Tale

August 30, 2021 by Kristina Panos 26 Comments

Those tiny switches inside your mouse may be rated for 50 million clicks or more, but your fingers will likely wear out much sooner than that. Trust us — mouse arm and/or hand fatigue is no fun at all. If you’ve never had the displeasure, just try to imagine not being able to click or move the mouse around without extreme discomfort.

For this year’s Hackaday Prize, [BinSun] hacked together a capacitive mouse for a friend who has ALS. Instead of micro switches, it uses touch sensors to detect left and right clicks and LEDs to indicate when a click has taken place. That makes us think that haptic feedback could be cool, but it might get old quickly, or even worse, you might get used to it after a while and not feel it anymore.

This mouse would be a good alternative for anyone with limited mobility from any condition — ALS, arthritis, trigger finger, or carpal/cubital tunnel syndrome. It would also benefit anyone who wants to mouse much more stealthily, like in a library, a small shared space, or late at night. The only downside we can see is that you’d either have to get used to hovering your fingers, or else learn to rest them out of the way of the capacitive buttons. Otherwise, you’re gonna actuate them more often than you really want to.

If you want to build one of these, you’ll find a nice set of instructions over on IO that includes the minor modifications necessary to make the TTP223 capacitive modules sensitive enough to detect the presence of a finger. All you really have to do is bridge a couple of pads, add a capacitor and remove the SMD LEDs. [Bin Sun] says this is an ongoing project. He’s gotten a handful of beta testers involved at this point, and is planning to make a dedicated PCB pretty soon. Squeak past the break for a couple of brief demonstrations.

The right kind of mouse can save your limbs, sure. Hack together a different type of mouse, and you might be able to save your crops from elephant raids.

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MIT’s Knitted Keyboard Is Quite A Flexible MIDI Controller

June 30, 2021 by Kristina Panos 7 Comments

There are only so many ways to make noise on standard instruments such as acoustic pianos. Their rigidity and inputs just don’t allow for a super-wide range of expression. On the other hand, if you knit your interface together, the possibilities are nearly endless. MIT’s new and improved knitted keyboard is an instrument like none other — it responds to touch, pressure, and continuous proximity, meaning that you can play it like a keyboard, a theremin, and something that is somewhere in between the two. Because it’s a MIDI interface, it can ultimately sound like any instrument you’ve got available in software.

The silver keys of this five-octave interface are made of conductive yarn, and the blue background is regular polyester yarn. Underneath that is a conductive knit layer to complete the key circuits, and a piezo-resistive knit layer that responds to pressure and stretch. It runs on a Teensy 4.0 and uses five MPR121 proximity/touch controllers, one per octave.

The really exciting thing about this keyboard is its musical (and physical) versatility. As you might expect, the keyboard takes discrete inputs from keystrokes, but it also takes continuous input from hovering and waving via the proximity sensors, and goes even further by taking physical input from squeezing, pulling, stretching, and twisting the conductive yarns that make up the keys. This means it takes aftertouch (pressure applied after initial contact) into account — something that isn’t possible with most regular instruments. And since this keyboard is mostly yarn and fabric, you can roll it up and take it anywhere, or wrap it around your neck for a varied soundscape.

If you’re looking for more detail, check out the paper for the previous version (PDF), which also used thermochromic yarn to show different colors for various modes of play using a heating element. With the new version, [Irmandy Wicaksono] and team sought to improve the sensing modalities, knitted aesthetics, and the overall tactility of the keyboard. We love both versions! Be sure to check it out after the break.

Want to play around with capacitive touch sensors without leaving the house for parts? Make your own from paper and aluminum foil.

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Polyphony On A Tiny Scale

May 9, 2021 by Jenny List 4 Comments

Older readers may remember the Stylophone, a small battery powered electric organ using conductive PCB pads and a stylus to create notes. The simple multivibrators in those instruments made them monophonic, but here in 2021 we can do better than that! [Sjm4306] has gone the extra mile with a PCB organ, by making a capacitive-touch instrument that boasts four-note polyphony.

At its heart is an ATmega328p whose software sports four tone generators that each emerge on a different pin. These are summed using a set of 100 Ω resistors and fed to a tiny speaker. Power comes from a CR2032 lithium cell, and he notes that a higher voltage delivers more volume.

The full story is detailed in the video below the break, along with a bit of four-note polyphonic action. We’re guessing that this instrument would sound sensational when hooked up to a reverb unit.

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