This Open Source Active Probe Won’t Break The Bank

June 13, 2024 by Dan Maloney 19 Comments

If you’re like us, the oscilloscope on your bench is nothing special. The lower end of the market is filled with cheap but capable scopes that get the job done, as long as the job doesn’t get too far up the spectrum. That’s where fancier scopes with active probes might be required, and such things are budget-busters for mere mortals.

Then again, something like this open source 2 GHz active probe might be able to change the dynamics a bit. It comes to us from [James Wilson], who began tinkering with the design back in 2022. That’s when he learned about the chip at the center of this build: the BUF802. It’s a wide-bandwidth, high-input-impedance JFET buffer that seemed perfect for the job, and designed a high-impedance, low-capacitance probe covering DC to 2 GHz probe with 10:1 attenuation around it.

[James]’ blog post on the design and build reads like a lesson in high-frequency design. The specifics are a little above our pay grade, but the overall design uses both the BUF802 and an OPA140 precision op-amp. The low-offset op-amp buffers DC and lower frequencies, leaving higher frequencies to the BUF802. A lot of care was put into the four-layer PCB design, as well as ample use of simulation to make sure everything would work. Particularly interesting was the use of openEMS to tweak the width of the output trace to hit the desired 50 ohm impedance.

OpenSCAD Cranks Out Parametric CNC Clamps

June 11, 2024 by Tom Nardi 7 Comments

If you’ve ever used a CNC router or mill, you’ll know how many little things need to go right before you get anything resembling acceptable results. We could (and probably should?) run a whole series of posts on selecting the correct bit for the job at hand and figuring out the appropriate feeds and speeds. But before you even get to that point, there’s something even more critical you need to do: hold the workpiece down so it doesn’t blast off into orbit when the tool touches it.

Now that might sound like an easy enough job, and for basic flat stock, it often is. But if you’ve got an oddly shaped piece of material, you’ll quickly realize how inadequate those trusty c-clamps really are. When you get to that point, it might time to check out these OpenSCAD hold down clamps from [ostat]. Thanks to its parametric nature, you can plug whatever dimensions you need into the script, and in a few seconds it will spit out an STL file for a bespoke clamp that you can print out and put to work.

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The Cheap CNC3018 Gets A Proper Revamp

June 8, 2024 by Dave Rowntree 24 Comments

Many people have been attracted to the low price and big dreams of the CNC3018 desktop CNC router. If you’re quick, you can pick one up on the usual second-hand sales sites with little wear and tear for a steal. They’re not perfect machines by any stretch of the imagination, but they can be improved upon, and undoubtedly useful so long as you keep your expectations realistic.

[ForOurGood] has set about such an improvement process and documented their journey in a whopping eight-part (so far!) video series. The video linked below is the most recent in the series and is dedicated to creating a brushless spindle motor on a budget.

As you would expect from such a machine, you get exactly what you pay for. The low cost translates to thinner than ideal metal plates, aluminium where steel would be better, lower-duty linear rails, and wimpy lead screws. The spindle also suffers from cost-cutting, as does the size of the stepper motors. But for the price, all is forgiven. The fact that they can even turn a profit on these machines shows the manufacturing prowess of the Chinese factories.

We covered the CNC 3018 a while back, and the comments of that post are a true gold mine for those wanting to try desktop CNC. Warning, though: It’s a fair bit harder to master than 3D printing!

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Gamma Ray Spectroscopy The Pomelo Way

June 5, 2024 by Dan Maloney 15 Comments

Depending on the circumstances you find yourself in, a Geiger counter can be a tremendously useful tool. With just a click or a chirp, it can tell you if any invisible threats lurk. But a Geiger counter is a “yes or no” instrument; it can only tell you if an ionizing event occurred, revealing nothing about the energy of the radiation. For that, you need something like this gamma-ray spectroscope.

Dubbed the Pomelo by [mihai.cuciuc], the detector is a homebrew solid-state scintillation counter made from a thallium-doped cesium iodide crystal and a silicon photomultiplier. The scintillator is potted in silicone in a 3D printed enclosure, to protect the hygroscopic crystal from both humidity and light. There’s also a temperature sensor on the detector board for thermal compensation. The Pomelo Core board interfaces with the physics package and takes care of pulse shaping and peak detection, while a separate Pomelo Zest board has an ESP32-C6, a small LCD and buttons for UI, SD card and USB interfaces, and an 18650 power supply. Plus a piezo speaker, because a spectroscope needs clicks, too.

The ability to determine the energy of incident photons is the real kicker here, though. Pomelo can detect energies from 50 keV all the way up to 3 MeV, and display them as graphs using linear or log scales. The short video below shows the Pomelo in use on samples of radioactive americium and thorium, showing different spectra for each.

[mihai.cuciuc] took inspiration for the Pomelo from this DIY spectrometer as well as the CosmicPi.

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Use That One Port For High-Speed FPGA Data Export

June 1, 2024 by Arya Voronova 7 Comments

There’s a good few options for exporting data out of FPGAs, like Ethernet, USB2, or USB3. Many FPGAs have a HDMI (or rather, sparkling DVI) port as well, and [Steve Markgraf] brings us the hsdaoh project — High-Speed Data Acquisition Over HDMI, using USB3 capture cards based on the Macrosilicon MS2130 chipset to get the data from the FPGA right to your PC.

Current FPGA-side implementation is designed for Sipeed Tang chips and the GOWIN toolchain, but it should be portable to an open-source toolchain in the future. Make sure you’re using a USB3 capture card with a MS2130 chipset, load the test code into your FPGA, run the userspace capture side, and you’re ready to add this interface to your FPGA project! It’s well worth it, too – during testing, [Steve] has got data transfer speeds up to 180 MB/s, without the USB3 complexity.

As a test, [Steve] shows us an RX-only SDR project using this interface, with respectable amounts of bandwidth. The presentation goes a fair bit into the low-level details of the protocol, from HDMI fundamentals, to manipulating the MS2130 registers in a way that disables all video conversion; do watch the recording, or at least skim the slides! Oh, and if you don’t own a capture card yet, you really should, as it makes for a wonderful Raspberry Pi hacking companion in times of need.

Quick & Capable WiFi For Your Nice-Power Supply

May 31, 2024 by Arya Voronova 12 Comments

Rejoice, those of us who have purchased a Nice-Power lab PSU from an Eastern source. Yes, the name might sound like a re-brand of a generic product, maybe you will even see this exact PSU on a shelf at a physical store near you, under a more local brand name and with a fair markup. Nevermind the circumstances, the most important part is that [Georgi Dobrishinov] found a way to add an ESP8266 to the PSU by tapping its internal UART control interface, and wrote a web UI for all your Internet-of-Lab-PSUs needs, called the PowerLinkESP project.

All you need is a Wemos D1 development board, or any other ESP8266 board that has UART pins exposed and handles 5 V input. [Georgi] brings everything else, from pictures showing you where to plug it in and where to tap 5 V, to extensive instructions on how to compile and upload the code, using just the Arduino IDE. Oh, and he tops it off with STLs for a 3D printed case, lest your Wemos D1 board flop around inside.

With [Georgi]’s software, you can monitor your PSU with interactive charts for all readings, export charts in both PNG and CSV, and access a good few features. Your ESP8266’s network uplink is also highly configurable, from an STA mode for a static lab config, to an AP mode for any on-the-go monitoring from your phone, and it even switches between them automatically! The firmware makes your PSU all that more practical, to the point that if you’re about to build an interface for your PSU, you should pay attention to [Georgi]’s work.

Lab PSUs with WiFi integration are worth looking into, just check out our review of this one; smart features are so nice to have, we hackers straight up rewrite PSU firmware to get there if we have to. Oh, and if you ever feel like standardizing your work so that it can interface to a whole world of measurement equipment, look no further than SCPI, something that’s easier to add to your project than you might expect, even with as little as Python and a Pi.

Schematic of the Pi Pico wireup, showing the various outputs that the firmware will generate on the GPIOs

A Scope Test Tool You Can Build With Just A Pico

May 31, 2024 by Arya Voronova 24 Comments

Ever wanted to see how well your oscilloscope adheres to its stated capabilities? What if you buy a new scope and need a quick way to test it lest one of its channels its broken, like [Paul Wasserman] had happen to him? Now you only need a Pi Pico and a few extra components to make a scope test board with a large variety of signals it can output, thanks to [Paul]’s Sig Gen Pi Pico firmware.

Despite the name it’s not a signal generator as we know it, as it’s not flexible in the signals it generates. Instead, it creates a dozen signals at more or less the same time — from square waves of various frequencies and duty cycles, to a PWM-driven DAC driving eight different waveforms, to Manchester-encoded data I2C/SPI/UART transfers for all your protocol decoder testing.

Everything is open source under the BSD 3-Clause license, and there’s even two PDFs with documentation and a user manual, not to mention the waveform screenshots for your own reference.

It’s seriously impressive how many features [Paul] has fit into a single firmware. Thanks to his work, whenever you have some test equipment in need of being tested, just grab your Pico and a few passive components.