Author: Matt Varian

36 Articles

Business Card-Tro

ATtiny-Powered Business Card Plays Cracktro Hits

July 29, 2025 by 11 Comments

These cards plug into a USB port for power and have over a dozen small LEDs that light up the stars on the front, and a small buzzer that can play over ten minutes of cracktro music. To keep the cost down, [VCC] went with an ATtiny1616 microcontroller costing under 50 cents and still having plenty of outputs to drive the buzzer and LEDs. The final per-unit cost prior to shipping came out to only 1.5 euros, enabling them to be handed out without worrying about breaking the bank.

To aid in the assembly of the cards, [VCC] 3D printed a jig to apply material to the back of the USB connector, building up its thickness to securely fit in the USB port. He also wrote a small script for assembly-line programming the cards, getting the programming process down to around ten seconds per card and letting him turn through prepping the cards. Thanks, [VCC], for sending in your project—it’s a great addition to other PCB business cards we’ve featured.

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RPI TinynumberHat9

2025 One Hertz Challenge: RPI TinynumberHat9

July 27, 2025 by 2 Comments

This eye-catching entry to the One Hertz Challenge pairs vintage LED indicators with a modern RPi board to create a one-of-a-kind clock. The RPI TinynumberHat9 by [Andrew] brings back the beautiful interface from high end electronics of the past.

This project is centered around the red AL304 and green ALS314V 7-segment display chips. These 7-segment displays were produced in the 1970s and 1980s in the Soviet Union; you can still find them, but you’ll have to do some digging as they are only becoming more rare. [Andrew] included the data sheet for these which was a good find, it is written in Russian but doesn’t hold any surprises, these tiny LEDs typically forward current is 5mA at 2V. One of the things that jumps out about these LEDs is the gold leads, a sure sign of being a high-end component of their day.

When selecting a driving chip for the LEDs, [Andrew] looked at the MAX7219 and HT16K33; he settled on the HT16K33 as it supports I2C as well as allows the easy addition of buttons to the HAT. Due to being driven by I2C, he was also able to add a Qwiic/Stemma I2C connector, so while designed initially to be a HAT for a Raspberry Pi Zero 2 W board, it can be connected to other things in the Qwiic/Stemma ecosystem.

Thanks [Andrew] for submitting this beautiful entry into the One Hertz Challenge. We love unique 7-segment displays, and so it’s pretty awesome to see 40-year-old display tech brought into the present.

2025 Hackaday One Hertz Challenge

 

Compass CNC

Human In The Loop: Compass CNC Redefines Workspace Limits

July 25, 2025 by 14 Comments

CNCs come in many forms, including mills, 3D printers, lasers, and plotters, but one challenge seems universal: there’s always a project slightly too large for your machine’s work envelope. The Compass CNC addresses this limitation by incorporating the operator as part of the gantry system.

The Compass CNC features a compact core-XY gantry that moves the router only a few inches in each direction, along with Z-axis control to set the router’s depth. However, a work envelope of just a few inches would be highly restrictive. The innovation of the Compass CNC lies in its reliance on the operator to handle gross positioning of the gantry over the workpiece, while the machine manages the precise, detailed movements required for cutting.

Most of the Compass CNC is constructed from 3D printed parts, with a commercial router performing the cutting. A Teensy 4.1 serves as the control unit, managing the gantry motors, and a circular screen provides instructions to guide the operator on where to position the tool.

Those familiar with CNC routers may notice similarities to the Shaper Origin. However, key differences set the Compass CNC apart. Primarily, it is an open source project with design files freely available for those who want to build their own. Additionally, while the Shaper Origin relies on a camera system for tracking movement, the Compass CNC uses four mouse sensors to detect its position over the workpiece.

The Compass CNC is still in development, and kits containing most of the necessary components for assembly are available. We’re excited to see the innovative creations that emerge from this promising new tool.

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Most complex blinking light

2025 One Hertz Challenge: 16-Bit Tower Blinks At One Hertz

July 23, 2025 by 3 Comments

We’ve seen our share of blinking light projects around here; most are fairly straightforward small projects, but this entry to the 2025 One Hertz Challenge is the polar opposite of that approach. [Peter] sent in this awesome tower of 16bit relay CPU power blinking a light every second.

There’s a lot to take in on this project, so be sure to go look at the ongoing logs of the underlying 16-bit relay CPU project where [Peter] has been showing his progress in creating this clicking and clacking masterpiece. The relay CPU consists of a stack of 5 main levels: the top board is the main control board, the next level down figures out the address calculations for commands, under that is the arithmetic logic unit level, under the ALU is the output register where you’ll see a 220 V lamp blinking at 1 Hz, and finally at the base are a couple of microcontrollers used for a clock signal and memory. [Peter] included oscilloscope readings showing how even with the hundreds of moving parts going on, the light is blinking within 1% of its 1 Hz goal.

It’s worth noting that while [Peter] has the relay CPU blinking a light in this setup, the CPU has 19 commands to program it, enabling much more complex tasks. Thanks for the amazing-sounding entry from [Peter] for our One Hertz Challenge. Be sure to check out some of the other relay computers we’ve featured over the years for more clicking goodness.

2025 Hackaday One Hertz Challenge

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3D printed rotary table

Bearing Witness: Measuring The Wobbles In Rotary Build

July 21, 2025 by 5 Comments

3D printing has simplified the creation of many things, but part of making something is knowing just how much you can rely on it. On the [BubsBuilds] YouTube channel, he built a cheap rotary table and then walked through the process of measuring the error inherent in any rotating system.

Starting with a commercial rotary table, [BubsBuilds] decided he wanted a rotary stage that was both lighter and had provisions for motorized movement. Most of the rotary build is 3D printed, with the large housing and table made from PETG, and the geared hub and worm gear printed on a resin printer. The bearings used to support the worm gear are common skateboard bearings. There is also a commercial thrust bearing and 49 larger 9.5 mm ball bearings supporting the rotating tabletop.

There are three different types of runout to be measured on a rotating stage: axial, radial, and angular. Axial runout is fairly straightforward to discern by measuring the vertical variation of the table as it rotates. Radial runout measures how true the rotation is around the center of the table. Angular runout measures how level the table stays throughout its range. Since these two runouts are tied to each other, [BubsBuilds] showed how you can take measurements at two different heights and use trigonometry to obtain both your radial and angular runout

This is a great walk-through of how to approach measuring and characterizing a system that has multiple variables at play. Be sure to check out some of the other cool rotary tables we’ve featured.

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USB VSense

USB-C Rainbow Ranger: Sensing Volts With Style

July 15, 2025 by 1 Comment

USB-C has enabled a lot of great things, most notably removing the no less than three attempts to plug in the cable correctly, but gone are the days of just 5V over those lines. [Meticulous Technologies] sent in their project to help easily identify what voltage your USB-C line is running at, the USB VSense.

The USB VSense is an inline board that has USB-C connectors on either end, and supporting up to 240W you don’t have to worry about it throttling your device. One of the coolest design aspects of this board is that it uses stacked PCB construction as the enclosure, the display, and the PCB doing all the sensing and displaying. And for sensing this small device has a good number of cool tricks, it will sense all the eight common USB-C voltages, but it will also measure and alert you to variations of the voltage outside the normal range by blinking the various colored LEDs in specific patterns. For instance should you have it plugged into a line that’s sitting over 48V the VSense white 48V LED will be rapidly blinking, warning you that something in your setup has gone horribly wrong.

Having dedicated uniquely colored LEDs for each common level allows you to at a glance know what the voltage is at without the need to read anything. With a max current draw of less than 6mA you won’t feel bad about using it on a USB battery pack for many applications.

The USB VSense has completed a small production run and has stated their intention to open source their design as soon as possible after their Crowd Supply campaign. We’ve featured other USB-C PD projects and no doubt we’ll be seeing more as this standard continues to gain traction with more and more devices relying on it for their DC power.

Cara robot dog

From Leash To Locomotion: CARA The Robotic Dog

July 13, 2025 by 9 Comments

Normally when you hear the words “rope” and “dog” in the same sentence, you think about a dog on a leash, but in this robot dog, the rope is what makes it move, not what stops it from going too far. [Aaed Musa]’s latest project is CARA, a robotic dog made mostly of 3D printed parts, with brushless motors and ropes used to tie the motors and legs together.

In a previous post, we covered [Aaed Musa]’s use of rope as a mechanism to make capstan drives, enabling high torque and little to no backlash. Taking that gearbox design, tweaking it a bit, and using three motors, he was able to make a leg capable of moving in all three axes. He had to do a good deal of inverse kinematics math to get the leg moving around as desired; once he had the motion of a step defined, it was time to build the rest of the dog.

CARA is made primarily of 3D printed parts, with several carbon fiber tubes running its length for rigidity. The legs are all free to move not only forward and back but side to side some, as in a real dog. He uses 12 large brushless motors, as they provide the torque needed, and ODrive S1 motor controllers to control each one, controlled over CAN by a Teensy 4.1 microcontroller. There is also a small BNO086 IMU to sense CARA’s position relative to gravity, and a 24V cordless tool battery powers everything.

Once assembled, there was some more tuning of what type of motion CARA’s legs take while walking. There were a few tweaks to the printed parts to address some structural issues, and then a good deal more inverse kinematics math to make full use of the IMU, allowing CARA to handle inclines and make a much more natural movement style. [Aaed Musa] does a great job explaining his approach on his site as well as in the video below; we’re looking forward to seeing his future projects!

CARA isn’t alone on this site—be sure to check out the other robot dogs we’ve featured here.

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