The Cutest Oscilloscope Ever Made

If you thought your handheld digital oscilloscope was the most transportable of your signal analyzing tools, then you’re in for a surprise. This oscilloscope made by [Mark Omo] measures only one square inch, with the majority of the space taken up by the OLED screen.

It folds out into an easier instrument to hold, and admittedly does require external inputs, so it’s not exactly a standalone tool. The oscilloscope runs on a PIC32MZ EF processor, achieving 20Msps and 1MHz of bandwidth. The former interleaves the processor’s internal ADCs in order to achieve its speed.

For the analog front-end the signals first enter a 1M ohm terminator that divide the signals by 10x in order to measure them outside the rails. They then get passed through a pair of diodes connected to the rails, clamping the voltage to prevent damage. The divider centers the incoming AC signal around 1.65V, halfway between AGND and +3.3V. As a further safety feature, a larger 909k Ohm resistor sits between the signals and the diodes in order to prevent a large current from passing through the diode in the event of a large voltage entering the system.

The next component is a variable gain stage, providing either 10x, 5x, or 1x gain corresponding to 1x, 0.5x, and 0.1x system gains. For the subsystem, a TLV3541 op-amp and ADG633 tripe SPDT analog switch are used to provide a power bandwidth around the system response due to driving concerns. Notably, the resistance of the switch is non-negligible, potentially varying with voltage. Luckily, the screen used in the oscilloscope needs 12V, so supplying 12V to the mux results in a lower voltage and thus a flatter response.

The ADC module, PIC32MZ1024EFH064, is a 12-bit successive approximation ADC. One advantage of his particular ADC is that extra bits of resolution only take constant time, so speed and accuracy can be traded off. The conversion starts with a sample and hold sequence, using stored voltage on the capacitor to calculate the voltage.

Several ADCs are used in parallel to sample at the same time, resulting in the interleaving improving the sample rate. Since there are 120 Megabits per second of data coming from the ADC module, the Direct Memory Access (DMA) peripheral on the PIC32MZ allows for the writing of the data directly onto the memory of the microcontroller without involving the processor.

The firmware is currently available on GitHub and the schematics are published on the project page.

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Minature Table Saw Gets The Teeny Jobs Done

Table saws are highly useful tools, but tend to take up a lot of space. They’re usually designed to handle the bigger jobs in a workshop. It doesn’t have to be that way, however, as [KJDOT] demonstrates with a miniature table saw.

It’s a saw that relies on a simple build. The frame is made of plywood, and can be built with just a drill and a hand saw. A brushed motor is used to run the saw, using an off-the-shelf PWM controller and a 24V power supply. A handful of bearings and standard brackets are then used to put it all together, and there’s even a handy adjustable fence to boot. With a 60mm blade fitted, the saw is ready to go.

It’s a build that would be great for anyone regularly working with wood or plastics on the smaller scale. If you like building dollhouses, this could be the tool for you. You might also find the table nibbler to be an enticing proposition. Video after the break.

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Tools, You Can’t Take Them With You

When I die I hope be buried in the English rural churchyard that has been my responsibility as churchwarden, after a funeral service that has been a celebration of my life. I am neither an Egyptian pharaoh nor a Viking queen though, so my grave will not contain all my tools and equipment to serve me in the afterlife. Instead aside from my mortal remains it will contain only a suitably biodegradable coffin, and my headstone will be a modest one bearing perhaps a technical puzzle to entertain visitors to the churchyard.

My workshop, my bench, and my tools will be the responsibility of my nearest and dearest, and I hope I will have suitably equipped them for the task of their dispersal. But for anyone who has a sizeable collection of gear, have you thought of what would happen if someone else had to clean it all out? What is profession for some and hobby for others, we deal in specialization that might as well be tools of arcane magic to the uninitiated.

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DIY Tiny Dovetail Cube Needs DIY Dovetail Cutter

Dovetail cutter, made from a 5 mm drill rod.

There’s a trinket called a dovetail cube, and [mitxela] thought it would make a fine birthday present. As you can see from the image, he was successful in creating a tiny version out of aluminum and brass. That’s not to say there weren’t challenges in the process, and doing it [mitxela] style means:

  • Make it tiny! 15 mm sides ought to do it.
  • Don’t have a tiny dovetail bit on hand, so make that as well.
  • Of course, do it all without CNC in free-machining style.
  • Whoops the brass stock is smaller than expected, so find a clever solution.
  • That birthday? It’s tomorrow, by the way.

The project was a success, and a few small learning experiences presented themselves. One is that the shape of a dovetail plays tricks on the human eye. Geometrically speaking, the two halves are even but it seems as though one side is slightly larger than the other. [mitxela] says that if he were to do it again, he’d make the aluminum side slightly larger to compensate for this visual effect. Also, deburring with a knife edge on such a small piece flattened the edges ever so slightly, causing the fit to appear less precise than it actually is.

Still, it was a success and a learning experience. Need more evidence that [mitxela] thrives on challenge? Take a look at his incredible vector game console project.

This Dibbling Plate Will Grow Your Love For Sowing

One of the best things about 3D printers and laser cutters is their ability to produce specialized tools that steal time back from tedious processes. Seed sowing is a great example of this. Even if you only want to sow one tray with two dozen or so seeds, you still have to fill the tray with soil, level it off, compress it evenly, and poke all the holes. When seed sowing is the kernel of your bread and butter, doing all of that manually will eat up a lot of time.

There are machines out there to do dibbling on a large scale, but [Michael Ratcliffe] has been dabbling in dibbling plates for the smaller-scale farm. He’s created an all-in-one tool that does everything but dump the soil in the tray. Once you’ve done that, you can use edge to level off the excess soil, compress it with the back side, and then flip to the bed-of-nails side to make all the holes at once. It comes apart easily, so anyone can replace broken or dulled dibblers.

[Michael] is selling these fairly cheaply, but you can find all the files and build instructions out there in the Thingiverse. We planted the demo video after the break.

More into micro-greens? 3D printing can feed that fixation, too.

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2D-Scanner Records Surfboard Profiles For Posterity

[Ryan Schenk] had a problem: he built the perfect surfboard. Normally that wouldn’t present a problem, but in this case, it did because [Ryan] had no idea how he carved the gentle curves on the bottom of the board. So he built this homebrew 2D-scanner to make the job of replicating his hand-carved board a bit easier.

Dubbed the Scanbot 69420 – interpretation of the number is left as an exercise for the reader, my dude – the scanner is pretty simple. It’s just an old mouse carrying a digital dial indicator from Harbor Freight. The mouse was gutted, with even the original ball replaced by an RC plane wheel. The optical encoder and buttons were hooked to an Arduino, as was the serial output of the dial indicator. The Arduino consolidates the data from both sensors and sends a stream of X- and Z-axis coordinates up the USB cable as the rig slides across the board on a straightedge. On the PC side, a Node.js program turns the raw data into a vector drawing that represents the profile of the board at that point. Curves are captured at various points along the length of the board, resulting in a series of curves that can be used to replicate the board.

Yes, this could have been done with a straightedge, a ruler, and a pencil and paper – or perhaps with a hacked set of calipers – but that wouldn’t be nearly as much fun. And we can certainly see applications for this far beyond the surfboard shop.

Soldering Your Own Soldering Iron

A device that even DIY enthusiasts don’t usually think to DIY is the humble soldering iron. Yet, that’s exactly what one Hackaday.io user did by building a USB-powered soldering pen with better performance than a $5 Chinese soldering pen.

The project draws inspiration from another Weller RT tip-based soldering pen by [vlk], although this project has a simpler display than an OLED. Slovakia-based maker [bobricius] was inspired by the DiXi ATSAMD11C14-based development board. The project uses the same 32-bit ATMEL ARM microcontroller with a USB bootloader, which makes updating the firmware a lot easier.

Two buttons control the heat (+/-) and the jack for the Weller RT soldering tip controls the power out with PWM. For the display, 20 Charlieplexed 3014 LEDs are used to show the temperature from 0-399. The last missing LED is left out since 5 GPIO pins can only drive 20 LEDs.

Assuming that the main heating controls stay the same as [vlk]’s project, the pen uses a current sensor and heating controller for PID control of a heating module, which connects to the SMT connector for the Weller RT soldering iron tip. The temperature sensor uses a an op-amp for amplification of the signal from a type K thermocouple.

While there aren’t currently GERBER files for the PCB yet, the project is based on the open-source OLED display soldering pen project by [vlk], whose schematic for the device is published.

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