Improved Technique For Resistive Divider Keypads

[Lauri Pirttiaho] from the [Swiss Knife of Electronics] channel explains how to simplify your resistive divider keypad design on

The usual method involves building a resistive ladder that gives unique and equally spaced voltages for each keypress. If you have just four or five discrete buttons, it isn’t terribly difficult, but if you have a 12- or 16-keypad matrix, things get complicated. [Lauri] looked into the past to come up with a better way, specifically a 646 page, 1 kg textbook from 1990 — Analogue Ic Design: The Current-Mode Approach by Toumazou, Lidgey, and Haigh. He learned that sometimes what’s hard to do in the voltage domain is easy in the current domain.

Normally you’d throw in some resistors to form different voltage dividers depending on which key is pressed, and read the resulting voltage off of a voltage divider with an ADC. But that means using the voltage divider equation, and the difference in voltage between keys can get very small. Dropping the voltage divider and measuring the current through a current mirror generates a linear voltage across its output load resistor that can be easily read by your microprocessor. And [Lauri] has posted an example of just such a program on his GitHub repository for an Arduino.

Heavy analog electronics, for sure, but something to keep in mind if you’re reading more than 12 keys. Do you have any examples of solving problems by looking into old and/or less-common techniques? Let us know in the comments below.

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Disguising The PS5 With A Custom Wood And Carbon Fiber Enclosure

The PlayStation 5 has a very distinctive enclosure that some love and others hate. Its design certainly does not lend itself to lying on its side, even though this is a more practical orientation for putting on a shelf in a TV console. [Matt] from [DIY Perks] decided to address this and built a custom wood and carbon fiber PS5 enclosure that looks good in any orientation.

He started by disassembling his PS5 and taking out only the main electronics unit, fan, and power supply. These were mounted on a carbon fiber baseplate using hexagonal threaded standoffs. The sides of the enclosure were constructed from dark walnut, with holes cut in the front and back for connectors and airflow. A long recess was cut in the front hole and covered with an ingenious carbon fiber cover which opens if you press it at one end and acts as the power button if you press it at the other end.

Matt paid close attention to the airflow routing of the original enclosure and copied it to the new one. Like the original, he used adhesive foam strips to direct the air through the heat sinks. The top cover is also carbon fiber, with an elegant honeycomb hole pattern with wood inserts for the air intake.

This is not [Matt]’s first custom PS5 enclosure. The other was a significantly more flashy brass incarnation of the original. Other custom enclosure he’s made include a wood PC case and a brass encased USB-C monitor. Continue reading “Disguising The PS5 With A Custom Wood And Carbon Fiber Enclosure”

3D Printed Joystick Using Spherical Flexure Joint

One of the many advancements brought about by 3D printing is the rapid development of compliant mechanisms and flexure joints. One such example is [jicerr]’s joystick, which uses a pair of spherical flexure joints recently developed by researchers from Delft University of Technology in the Netherlands, See the videos after the break.

Both flexure joint designs make use of tetrahedron-shaped elements, allowing an object to pivot around a fixed point in space like a ball-and-socket joint. One of the joints, named Tetra 2, is perfect for printing on a standard FDM printer, and the 3D files were uploaded to Thingiverse by [Jelle_Rommers], one of the researchers. [jicerr] took the design and created a base to mount an HMC5883 3-axis magnetometer a short distance from the focal point, which senses the rotation of a small magnet at the focal point. An Arduino takes the output from the magnetometer, does the necessary calculation, and interfaces to a PC as a joystick. Demonstrates this by using it to rotate and pan the design in Solidworks. One thing to keep in mind with this design is that it needs a fixed base to prevent it from moving around. It should also be possible to integrate the design directly into the housing of a controller.

Another amusing application is to turn it into a pen holder with a chicken head on the front, as demonstrated by [50Pro]. If you have any ideas for other applications, drop them in the comments.

Compliant mechanisms have a number of interesting applications, including harmonic drives, dial indicators and thrust vectoring mounts.

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A High Power Wood Rocket In 5 Days

Getting started with model rocketry is relatively cheap and easy, but as you move up in high power rocketry, there are a few hoops to jump through. To be able to buy rocket motors larger than H (160 N·s / 36 lbf·s impulse) in the US, you need to get certified by the National Association of Rocketry. The main requirement of this certification involves building, flying, and recovering a rocket with the specific motor class required for the certification level. [Xyla Foxlin] had committed to doing her Level 2 certification with a couple of friends, thanks to the old procrastination monster, was forced to build a rocket with only 5 days remaining to launch data.

For Level 2 certification, the rocket needs to fly with a J motor, which is capable of producing more than 640 N·s of impulse. Fortunately [Xyla] had already designed the rocket in OpenRocket, and ordered the motor and major body, nosecone, and parachute components. The body was built around 2 sections of 3″ cardboard tubes, which are covered in a few layers of fiberglass. The stabilizing fins were laser cut from cheap plywood and were epoxied to the inner tube which holds the motor and passes through the sides of the outer tube. The fins are also fibreglassed to increased strength. For a unique touch, she covered the rocket with a real wood veneer, with the rocket’s name, [Fifi], inlaid with darker wood. The recovery system is a basic parachute, connected to the rocket body with Kevlar rope.

[Xyla] finished her rocket just in time for the trek out to the rocket range. She successfully did the certification flight and recovered [Fifi] in reusable condition, which is a requirement. There was nothing groundbreaking about [Fifi], but then again, reliability the main requirement. You don’t want to do a certification with a fancy experimental rocket that could easily fail. Continue reading “A High Power Wood Rocket In 5 Days”

With A Big Enough Laser, The World Is Your Sensor

It’s difficult to tell with our dull human senses, but everything around us is vibrating. Sure it takes more energy to get big objects like bridges and houses humming compared to a telephone pole or mailbox, but make no mistake, they’ve all got a little buzz going on. With their new automated laser, the team behind VibroSight++ believes they can exploit this fact to make city-scale sensing far cheaper and easier than ever before.

The key to the system is a turret mounted Class 3B infrared laser and photodetector that can systematically scan for and identity reflective surfaces within visual range. Now you might think that such a setup wouldn’t get much of a signal from the urban landscape, but as it so happens, the average city block is packed with retroreflectors. From street signs to road studs and license plates, the team estimates dense urban areas have approximately 7,000 reflectors per square kilometer. On top of those existing data points, additional reflectors could easily be added to particularly interesting devices that city planners might want to monitor.

Once VibroSight++ has identified its targets, the next step is to bounce the laser off of them and detect the minute perturbations in the returned signal caused by vibrations in the reflector. In the video below you can see how this basic concept could be put to practical use in the field, from counting how many cars pass over a certain stretch of road to seeing how popular a specific mailbox is. There’s a whole world of information out there just waiting to be collected, all without having to install anything more exotic than the occasional piece of reflective tape.

If this technology seems oddly familiar, it’s probably because we covered the team’s earlier work that focused (no pun intended) on using reflected laser beams for home automation in 2018. Back then they were aiming a much smaller laser at blenders and refrigerators instead of license plates and street signs, but the concept is otherwise the same. While we’ll admit the technology does give off a distinctive Orwellian vibe, it’s hard not to be intrigued by the “Big Data” possibilities afforded by the team’s upgraded hardware and software.

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Rodriguez — IV Curve Tracer On The Cheap

In response to an online discussion on the Electrical Engineering Stack Exchange, [Joseph Eoff] decided to prove his point by slapping together a bare-bones IV curve tracer using an Arduino Nano and a handful of passives. But he continued to tinker with the circuit, seeing just how much improvement was possible out of this simple setup. He squeezes a bit of extra resolution out of the PWM DAC circuit by using the Timer1 library to obtain 1024 instead of 256 steps. For reading voltages, he implements oversampling (and in some cases oversampling again) to eke out a few extra bits of resolution from the 10-bit ADC of the Nano. The whole thing is controlled by a Python / Qt script to generate the desired plots.

While it works and gives him the IV curves, this simplicity comes at a price. It’s slow — [Joseph] reports that it takes several minutes to trace out five different values of base current on a transistor. It was this lack of speed that inspired him to name the project after cartoon character Speedy Gonzales’s cousin,  Slowpoke Rodriguez, AKA “the slowest mouse in all of Mexico”. In addition to being painstakingly slow, the tracer is limited to 5 volts and currents under 5 milliamps.

[Joseph] documents the whole design and build process over on his blog, and has made the source code available on GitHub should you want to try this yourself. We covered another interesting IV curve tracer build on cardboard ten years ago, but that one is much bigger than the Rodriguez.

A Phased-Array Ultrasonic 3D Scanner From Scratch

Who wouldn’t want an autonomous drone to deliver cans of fizzy drink fresh from the fridge? [Alex Toussaint] did, and in thinking how such a machine might work he embarked on a path that eventually led him to create a fully functional ultrasonic 3D scanner. In writing it up he’s produced a straightforward description of how the system works, which should also be of interest to anyone curious about phased array radar. He starts with an easy-to-understand explanation of the principle behind phased array beam forming, and there follows his journey into electronics as he uses this ambitious project to learn the art from scratch. That he succeeded is testament to his ability as well as his sheer tenacity.

He finally arrived at a grid of 100 ultrasonic emitters controlled from an Arduino through a series of shift register boards. Using this he can steer his ultrasonic beam horizontally as well as vertically, and receive echoes from objects in three-dimensional space. The ornamental bird example he uses for his scanning tests doesn’t quite emerge in startling clarity, but it is still clear that an object of its size and rough shape is visible enough for the drone in his original idea to detect it. If you would like to experiment with the same techniques and array then all the resources can be found in a GitHub repository, meanwhile we’re still impressed with the progress from relative electronics novice to this. We hope the ideas within it will be developed further.

We’ve seen ultrasonic arrays before, but mainly used in levitation experiments.