A Modern Tribute To The Classic HP-16C Calculator

December 21, 2022 by Zoe Skyforest 19 Comments

The HP-16C Computer Scientist is much beloved as the only dedicated programmer’s calculator that Hewlett-Packard ever made. Most surviving examples in the world are well-used, and you haven’t been able to order one from HP since 1989. Thus, [K Johansen] set about building a tribute to the HP-16C using modern hardware.

The build relies on a Raspberry Pi Pico as the brains of the operation. As with so many classic HP calculators, it operates in Reverse Polish Notation, and includes the customary stack operations. To serve a programmer well, it’s set up to accept entry in hexadecimal, octal, decimal, and binary formats, and can readily convert between them. Beyond that, it’s equipped with the usual arithmetic operators, as well as bitwise operations like NOT, AND, and so on.

Perhaps what we love most, though, is the keypad. It was all put together with a combination of cheap AliExpress keypads, a label maker, and a laser printer. It’s a wholly DIY job, and a little rough around the edges, but it makes the calculator far easier to use.

It’s not an exact replica of the HP-16C, but the differences in operation are minor.Those wishing to build their own can grab the required files from the project’s Github page. We’ve seen replicas of other classic HP calculators before, too. If you’ve got your own mathematical projects brewing up in the lab, don’t hesitate to send them in to the tipsline!

LED Christmas Lights Optimized For Max Twinkleage

December 21, 2022 by Zoe Skyforest 12 Comments

Old-school filament-based Christmas lights used to be available in twinkling form. LEDs, with their hard-on and hard-off nature, aren’t naturally predisposed to such behavior. To rectify this, some time ago, [Mark Kriegsman] built an Arduino program that makes LEDs twinkle beautifully.

The program is known as TwinkleFOX, and relies on the popular FastLED library for addressable LEDs. [Mark’s] demo setup is built around using WS2811 LEDs, put together in a string with plastic diffusers on each bulb. The Arduino is programmed to vary the brightness of each LED according to a triangle wave function. To create the twinkling effect, each LED has its own unique clock signal, so they vary in brightness at different times and at different rates.

Using an Arduino Uno or Leonardo, [Mark] reports its possible to twinkle 300 individual LEDs at a rate of over 50 updates a second. Using a faster microcontroller should net reliable performance with longer strings. Meanwhile, if you’re wondering how the older-style lights used to twinkle, we’ve covered that before too. Video after the break.

Continue reading “LED Christmas Lights Optimized For Max Twinkleage” →

2022 FPV Contest: The LOTP Robot Dog

December 21, 2022 by Zoe Skyforest 7 Comments

When you think of first person view (FPV) vehicles, aircraft might be what first comes to mind. However, [Limenitis Reducta] has brought a robot dog into the world, and plans to equip it for some FPV adventures.

LOTP pictured with various equippable modules.

The robot dog itself goes by the name of LOTP, for unspecified reasons, and was designed from the ground up in Fusion 360. A Teensy 3.5 is charged with running the show, managing control inputs and outputting the requisite instructions to the motor controllers to manage the walk cycle. Movement are issued via a custom RC controller. Thanks to an onboard IMU, the robotic platform is able to walk effectively and maintain its balance even on a sloping or moving platform.

[Limenitis] has built the robot with a modular platform to support different duties. Equitable modules include a sensor for detecting dangerous gases, a drone launching platform, and a lidar module. There’s also a provision for a camera which sends live video to the remote controller. [Limenitis] has that implemented with what appears to be a regular drone FPV camera, a straightforward way to get the job done.

It’s a fun build that looks ready to scamper around on adventures outside. Doing so with an FPV camera certainly looks fun, and we’ve seen similar gear equipped on other robot dogs, too.

Continue reading “2022 FPV Contest: The LOTP Robot Dog” →

Blood Pressure Monitoring, Courtesy Of Cameras And AI

December 21, 2022 by Zoe Skyforest 60 Comments

At the basic level, methods of blood pressure monitoring have slowly changed in the last few decades. While most types of sphygmomanometer still rely on a Velcro cuff placed around the arm, the methodology used in measurement varies. Analog mercury and aneroid types still abound, while digital blood pressure monitors using electrical sensors have become mainstream these days.

Researchers have now developed a new non-invasive method of measurement that does away with the arm cuff entirely. The method relies entirely on video capture with a camera and processing via AI.

Continue reading “Blood Pressure Monitoring, Courtesy Of Cameras And AI” →

Differential Swerve Drive Is Highly Maneuverable

December 17, 2022 by Zoe Skyforest 17 Comments

There are a variety of wheel designs out there that can provide for rotation and translation in various directions. The differential swerve drive, though, as demonstrated by [WildWillyRobots], uses regular wheels on a complex mount to achieve impressive directional flexibility.

The design uses a regular round wheel mounted on an axle, which has a gear on one end. This allows the wheel to be driven. The wheel and axle is mounted upon a circular carrier, which is then fitted with a pair of surrounding gears on bearings. Differentially driving these gears changes the way the drive behaves. With both gears driven in the same direction, the wheel rotates on its vertical axis to point in different directions. If both gears are driven in opposite direction, the wheel itself is driven. Relatively varying the speed of both gears allows the direction and drive of the wheel to be controlled. The result is a wheel that can rotate to any angle, and then be driven forwards or backwards as well.

Fitting a set of these wheels to a robot creates a highly maneuverable platform. As a bonus, it doesn’t have the drawback of poor grip that is common with various omniwheel-type designs.

Continue reading “Differential Swerve Drive Is Highly Maneuverable” →

A Simple High-Fidelity DIY Mic Pre Amp

December 16, 2022 by Zoe Skyforest 13 Comments

If you’re doing any serious work with microphones, you’ll typically find yourself in want of a dedicated preamp. [ojg] needed just such a thing for acoustic measurement duties, and set about working up a cheap DIY design by the name of ThatMicPre.

The design is based around the THAT1510 preamp IC, known for its good frequency response and low harmonic distortion and noise. The design is also compatible with THAT1512, SSM2019, and INA217 chips as well. [ojg] gave the design switch-controlled gain levels, providing greater accuracy than a potentiometer adjustment, and the ability to supply phantom power for mics that require it. The PCB is designed to rely on through-hole parts and common connectors for easy assembly.

The design is open source, and has already been built by others on the DIYAudio forums. Built into a simple case, it looks like a handsome and well-built piece of audio equipment. We’ve featured quite a few unique preamps over the years, and if you’ve been building your own, we’d love to see those too!

Foot Pedal Ups Vim Productivity, Brings Ergonomic Benefits

December 16, 2022 by Zoe Skyforest 53 Comments

Vim is the greatest or the worst text editor of all time, depending on the tribe you’re in. Either way, members of both camps can appreciate this build from [Chris Price], which uses a foot pedal to ease operations for the user.

The basic concept was to use a pedal to enable switching between normal and insert modes. In Vim’s predecessor, vi, switching modes was easy, with the ESC key located neatly by the Q on the keyboard of the ADM-3A terminal. On modern keyboards, though, it’s a pain, and so a foot pedal is a desirable solution. In the Vim world, it’s referred to as a “Vim clutch.”

The build used a cheap pedal switch sourced from eBay, into which a Raspberry Pi Pico was installed. The Pico was hooked up to the switch contacts, and programmed to act as a USB HID device. When the pedal is pressed down, the Pico sends an “i” keypress to enter Vim’s insert mode. Releasing the pedal has the Pico send a “ESC” keypress to return to normal mode.

Those that use Vim on a regular basis would likely appreciate the productivity improvements of such a device. Plus, there’s some ergonomic benefits to not having to strain one’s hand over to reach the ESC key. Of course, it’s an old-school solution, but there’s still something so compelling and next-level about having a foot pedal hooked up to one’s dev rig.