Rotary encoders are critical to many applications, even at the hobbyist level. While considering his own rotary encoding needs for upcoming projects, it occurred to [Jan Mrázek] to try making his own DIY capacitive rotary encoder. If successful, such an encoder could be cheap and very fast; it could also in part be made directly on a PCB.
The encoder design [Jan] settled on was to make a simple adjustable plate capacitor using PCB elements with transparent tape as the dielectric material. This was used as the timing element for a 555 timer in astable mode. A 555 in this configuration therefore generates a square wave that changes in proportion to how much the plates in the simple capacitor overlap. Turn the plate, and the square wave’s period changes in response. Response time would be fast, and a 555 and some PCB space is certainly cheap materials-wise.
The first prototype gave positive results but had a lot of problems, including noise and possibly a sensitivity to temperature and humidity. The second attempt refined the design and had much better results, with an ESP32 reliably reading 140 discrete positions at a rate of 100 kHz. It seems that there is a tradeoff between resolution and speed; lowering the rate allows more positions to be reliably detected. There are still issues, but ultimately [Jan] feels that high-speed capacitive encoders requiring little more than some PCB real estate and some 555s are probably feasible.
The rabbit hole of features and clever hacks in [chiprobot]’s NEMA17 3D Printed Linear Actuator is pretty deep. Not only can it lift 2kg+ of mass easily, it is mostly 3D printed, and uses commonplace hardware like a NEMA 17 stepper motor and a RAMPS board for motion control.
The main 3D printed leadscrew uses a plug-and-socket design so that the assembly can be extended easily to any length desired without needing to print the leadscrew as a single piece. The tip of the actuator even integrates a force sensor made from conductive foam, which changes resistance as it is compressed, allowing the actuator some degree of feedback. The force sensor is made from a 3M foam earplug which has been saturated with a conductive ink. [chiprobot] doesn’t go into many details about his specific method, but using conductive foam as a force sensor is a fairly well-known and effective hack. To top it all off, [chiprobot] added a web GUI served over WiFi with an ESP32. Watch the whole thing in action in the video embedded below.
[chiprobot] is no stranger to DIY linear actuators, you can see his gearmotor version and stepper version on Thingiverse. He’s certainly stepped it up in terms of power and size with this Hackaday Prize Entry.
The naming and remixing in this project can get a little confusing to those unfamiliar with the different elements involved, but what [John Gerrard] has done is take a stylish mini arcade cabinet intended as a fancy peripheral for an iPad and turned it into an iPad-free retro arcade gaming cabinet. He also designed his own power controller for graceful startup and shutdown.
The project started with a peripheral called the iCade (originally conceived as a fake product for April Fool’s) and [John] observed it had good remix potential for use as a mini retro gaming cabinet. It was a good starting point: inexpensively purchased off eBay with suitable arcade-style joystick and buttons, a nice layout, and plenty of hacking potential. With a small variety of hardware from familiar sources like eBay and Aliexpress, [John] rounded up most of what he needed.
The core of the new machine is RetroPie on a Raspberry Pi 3, and the screen is a replacement iPad 2 LCD combined with a controller that accepts HDM. The display matches the cabinet well and the adapter allows for easy interface with the Raspberry Pi 3.
The cabinet’s buttons and joystick are re-wired to an Arcade USB controller. Other additions include speakers and Player 1/Player 2 start buttons. We’ve seen scratch-built RetroPie mini cabinets but [John] made excellent use of the existing hardware of the iCade, even going the extra mile and turning the fake 25 cent coin slot into a touch-sensitive button to add credits. The end result works, looks great, and is only a black bezel for the LCD away from being completely done.
A University of Utah team have a working prototype of a new twist on fluid-filled lenses for correction of vision problems: automatic adjustment and refocus depending on what you’re looking at. Technically, the glasses have a distance sensor embedded into the front of the frame and continually adjust the focus of the lenses. An 8 gram, 110 mAh battery powers the prototype for roughly 6 hours.
Eyeglasses that can adapt on the fly to different focal needs is important because many people with degraded vision suffer from more than one condition at the same time, which makes addressing their vision problems more complex than a single corrective lens. For example, many people who are nearsighted or farsighted (where near objects and far objects are seen out of focus, respectively) also suffer from a general loss of the eye’s ability to change focus, a condition that is age-related. As a result, people require multiple sets of eyeglasses for different conditions. Bifocal or trifocal or progressive lenses are really just multiple sets of lenses squashed into a smaller form factor, and greatly reduce the wearer’s field of view which is itself a significant vision impairment. A full field of view could be restored if eyeglass lenses were able to adapt to different needs based on object distance, and that is what this project achieves.
A real innovation is not actually the distance-sensing part, but the adjustable lenses themselves. Lenses that can be modified dynamically using various methods (fluid pumps, etc) exist, but the team found none that:
Had a wide enough field of view to serve effectively as corrective eyeglass lenses
Were small and lightweight enough to use in eyeglasses
Had minimal optical aberrations (no diffraction from fresnel grooves, no air gaps, and so forth)
In the solution the team created, the lens assembly is fluid filled and the front of the lens is a clear flexible membrane, but the rear of the lens acts as an optically clear piston controlled by three piezoelectric actuators. The design is small, light, can produce plano-convex or plano-concave lenses, and can do so quickly (within 15 ms) and with low power consumption. The full whitepaper is available online and contains details about testing, design, and construction.
The prototype looks like it has a 3D printed frame, and we’ve seen some DIY work in the past with 3D printing experiments with fluid-filled lenses.
Wanting to experiment with using optical mouse sensors but a bit frustrated with the lack of options, [Tom Wiggins] rolled his own breakout board for the ADNS 3050 optical mouse sensor and in the process of developing it used it to make his own 3D-printed optical mouse. Optical mouse sensors are essentially self-contained cameras that track movement and make it available to a host. To work properly, the sensor needs a lens assembly and appropriate illumination, both of which mate to a specialized bracket along with the sensor. [Tom] found a replacement for the original ADNS LED but still couldn’t find the sensor bracket anywhere, so he designed his own.
The github repository contains all the design files as well as Arduino libraries. Thinking others might share his interest in an easy to use breakout board for the ADNS 3050 that doubles as the mounting bracket, [Tom] started a Kickstarter campaign for a small production run.
Optical mouse sensors have often shown up as experimental movement trackers in hobby robotics, and even as low-res cameras. There’s a lot going on in these little packages and [Tom]’s fully documented open-source design tries to make it more accessible.