Using A Spring As A Capacitive Touch Button

May 22, 2024 by Maya Posch 18 Comments

When [Daniel Eichhorn] designed the Pendrive S3 project, he wanted to use an off-the-shelf USB enclosure but also add a button for the user to start certain actions. Drilling a hole into the enclosure would be an option, but decided a touch sensor on the top of the enclosure would be much more elegant — not to mention better at keeping dirt and moisture out. To bridge the 6.3 mm spacing between the PCB and the top of the enclosure [Daniel] used a small, 7 mm PCB-mounted spring.

The spring used to create a capacitive touch sensor. (Source: JLCPCB parts)

Although capacitive sensing works with just about anything that’s electrically conductive, it’s important to get the conductive element as close to the user’s digits as possible. Using a spring here has the advantage that when the enclosure is closed up, the lid will push down onto the spring, which will not only compress slightly, but also provide the best capacitive sensing experience when e.g. the enclosure flexes or warps over time on account of always being pressed against the inside of the lid.

While hardly world-changing, this is another neat design tip when you’re looking to turn more surfaces into touch controls. Just keep in mind that capacitive sensing is notoriously fussy and any trace and spring are also excellent antennae for stray EMI. Nobody likes random capacitive button inputs, after all.

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.

Touch-Typing On Fingertips? Prototype Says It Could Work

May 9, 2020 by Donald Papp 11 Comments

The fingertips are covered in touch sensors, each intended to be tapped by the thumbtip of the same hand.

Touch-typing with thumbs on a mobile phone keyboard is a pretty familiar way to input text, and that is part of what led to BiTipText, a method of allowing bimanual text input using fingertips. The idea is to treat the first segments of the index fingers as halves of a tiny keyboard, whose small imaginary keys are tapped with the thumbs. The prototype shown here was created to see how well the concept could work.

The prototype hardware uses touch sensors that can detect tap position with a high degree of accuracy, but the software side is where the real magic happens. Instead of hardcoding a QWERTY layout and training people to use it, the team instead ran tests to understand users’ natural expectations of which keys should be on which finger, and how exactly they should be laid out. This data led to an optimized layout, and when combined with predictive features, test participants could achieve an average text entry speed of 23.4 words per minute.

Judging by the prototype hardware, it’s understandable if one thinks the idea of fingertip keyboards may be a bit ahead of its time. But considering the increasingly “always on, always with you” nature of personal technology, the goal of the project was more about investigating ways for users to provide input in fast and subtle ways. It seems that the idea has some merit in principle. The project’s paper can be viewed online, and the video demonstration is embedded below.

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Robot Joints Go Modular With This Actuator Project

October 22, 2019 by Donald Papp 4 Comments

[John Lauer] has been hard at work re-thinking robot arms. His project to create modular, open source actuators that can be connected to one another to form an arm is inspiring, and boasts an impressively low parts cost as well. The actuators are each self-contained, with an ESP32 and a design that takes advantage of the form factors of inexpensive modules and parts from vendors like Aliexpress.

Flex spline in action, for reducing backlash

Each module has 3D printed gears (with an anti-backlash flex spline), an RGB LED for feedback, integrated homing, active cooling, a slip ring made from copper tape, and a touch sensor dial on the back for jogging and training input. The result is a low backlash, low cost actuator that keeps external wiring to an absolute minimum.

Originally inspired by a design named WE-R2.4, [John] has added his own twist in numerous ways, which are best summarized in the video embedded below. That video is number three in a series, and covers the most interesting developments and design changes while giving an excellent overview of the parts and operation (the video for part one is a basic overview and part two shows the prototyping process, during which [John] 3D printed the structural parts and gears and mills out a custom PCB.)

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Hack My Wired Heart

June 12, 2019 by Helen Leigh 3 Comments

Liner notes? Passé. In Berlin, the release of a special edition synth-wave record came with an accompanying experimental synthesizer called Wired Heart.

At the core of this adorable heart-shaped synth, designed by music technology enthusiast [tobi tubbutec], is the classic 74HCT14 chip with six Schmitt trigger oscillators. The bright red PCB has eight gold touch and humidity sensing pads that activate and modulate these oscillators. As well as changing the sounds by playing with pressure and conductive liquids you can use the six sets of header pins on board to plug in your own components for noisy experimentation. Wired Heart ships with LEDs, photoresistors and a potentiometer, but we’ve also plugged our own DIY fabric pressure sensors into this synth to make some excellent electronic sounds.

In the Hackaday.io post linked above, [tobi tubbutec] walks us through a number of the circuit design decisions he made while prototyping his “cardiotronic human-touch hexoscillatric stereo esoteric snythespacer”. We enjoyed his creative and sometimes unconventional designs, from his inclusion of non-functioning traces for aesthetic reasons to his chosen method of hard syncing — injecting a small pulse of one oscillator into the other. If you want to examine his layout in more detail, [tobi tubbutec] has helpfully included the KiCad schematic file in his write up.

This adorable, hackable synth caught our eye at this year’s SuperBooth — an annual indie electronic music conference in Berlin that’s well worth checking out if odd noises and handmade electronics are your thing — but it’s recently been listed on Tindie too. To listen to the upbeat synth-wave record Wired Heart originally shipped with, visit the artist Hyboid’s bandcamp.

If you’re interested in experimental musical instruments and synthy chip tune you’ll also love [jarek319]’s Sega Genesis synthesiser.

Check out a demo of the Wired Heart synth in the video after the break.

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ESP32 Alarm Clock Doesn’t Skimp On The Features

April 11, 2019 by Tom Nardi 11 Comments

The ESP family of microcontrollers is absolutely on fire right now, with a decent chunk of the projects that come our way now based on one of the impossibly cheap WiFi-enabled boards. In fact, they are so cheap and popular that we’ve started to see a somewhat unexpected trend; people have a tendency to use them as drop-in replacements, despite the more modern boards being considerably more powerful than required. The end result is a bunch of projects in which the ESP is simply underutilized. It’s not a big deal, but somewhat disappointing to see.

But we can assure you this ESP32 alarm clock created by [Pangodream] is absolutely not one of them. He’s packed an impressive number of features into this unassuming little timepiece, and it’s really an excellent example of how much these boards are capable of without breaking a sweat. From DIY touch sensors to the Android application used to configure the clock over the network, this project is overflowing with neat hardware and software tricks worth taking a closer look at.

Inside the 3D printed case, the clock features a BH150 light sensor, the very popular DHT-11 for detecting temperature and humidity, as well as a ILI9341 2.8 inch LCD for the display. In a particularly clever touch (get it?), [Pangodream] used three coins connected to the digital pins of the ESP32 as capacitive sensors. These allow him to interact with the click just by tapping the top of the case, and saved him the trouble of adding traditional switches or buttons. We might have put some indentations in the top case to make identifying which of the three “buttons” you’re pushing, but we suppose the invisible interface does make things look a little more futuristic.

But if even that is too much physical touching for you, then [Pangodream] has come up with a fairly robust system for controlling and interacting with the clock over the network. It’s not just a convenient way of setting the time, a good number of the clock’s functions can be polled and configured in this manner; everything from the sensitivity of the touch sensors to how many times it will beep when the alarm goes off. To make things easier, he’s even wrapped it all up in a handy Android application for on the go configuration.

If this clock doesn’t offer you the level of over-engineering you require, check out this build that uses no less than five ESP32s to get the job done. Or maybe this one that hooks into NASA’s Deep Space Network.

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Send Smooches Over Skype With The Kiss Interface

September 23, 2018 by Donald Papp 14 Comments

This project of [Nathan]’s certainly has a playful straightforwardness about it. His Skype ‘Kiss’ Interface has a simple job: to try to create a more intuitive way to express affection within the limits of using Skype. It all came about from a long distance relationship for which the chat program was the main means of communicating. Seeking a more intuitive and personal means of expressing some basic affection, [Nathan] created a capacitive touch sensor that, when touched with the lips, sends the key combination for either a kissy face emoji or the red lips emoji, depending on the duration.

Capacitive touch sensing allows for triggering the sensor without actually physically touching one’s lips to the electrodes, which [Nathan] did by putting a clear plastic layer over the PCB traces. His board uses an STM32 microcontroller with software handling the USB HID and STM’s TSC (Touch Sensing Controller) functionality. As a result, the board has few components and a simple interface, which was in keeping with the goal of rejecting feature creep and focusing on a simple task.

Clearly the unit works; but how well does it actually fulfill its intended purpose? We don’t know that yet, but we do know that [Nathan] seems to have everything he needs in order to find out. Either way, it’s a fun project that definitely fits the spirit of the Human-Computer Interface Challenge of The Hackaday Prize.