Better Scope Measurements

September 22, 2022 by Al Williams 6 Comments

There was a time when few hobbyists had an oscilloscope and the ones you did see were old military or industrial surplus that were past their prime. Today you can buy a fancy scope for about what those used scopes cost that would have once been the envy of every giant research lab. However, this new breed of instrument is typically digital and while they look like an old analog scope, the way they work leads to some odd gotchas that [Arthur Pini] covers in a recent post.

Some of his tips are common sense, but easy to forget about. For example, if you stack your four input channels so each uses up a quarter of the screen, it makes sense, right? But [Arthur] points out that you are dropping two bits of dynamic range, which can really jack up a sensitive measurement.

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Frequency Counter Restoration Impeded By Kittens

August 24, 2022 by Al Williams 12 Comments

We think of digital displays as something you see on relatively modern gear. But some old gear had things like nixies or numitrons to get cool-looking retro digital displays. The HP 521A frequency counter, though, uses four columns of ten discrete neon bulbs to make a decidedly low-tech but effective digital display. [Usagi Electric] has been restoring one of these for some time, but there was a gap between the second and third videos as his workshop became a kitten nursery. You can see the last video below.

In previous videos, he had most of the device working, but there were still some odd behavior. This video shows the final steps to success. One thing that was interesting is that since each of the four columns are identical, it was possible to compare readings from one decade to another.

However, in the end, it turned out that the neon bulbs were highly corroded, and replacing all the neon bulbs made things work better. However, the self-check that should read the 60 Hz line frequency was reading 72 Hz, so it needed a realignment. But that was relatively easy with a pot accessible from the back panel. If you want to see more details about the repair, be sure to check out the earlier videos.

We love this old gear and how clever designers did so much with what we consider so little. We hate to encourage your potential addiction, but we’ve given advice on how to acquire old gear before. If you want to see what was possible before WS2812 panels, you could build this neon bulb contraption.

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Mapping Out The LEDs On An Outlet Tester

August 9, 2022 by Tom Nardi 13 Comments

The concept of an outlet tester is pretty simple: plug the gadget into a suspect wall receptacle, and an array of LEDs light up in various patterns to alert the user to any wiring faults. They’re cheap, reliable, and instantaneous. Most people wouldn’t give them much more thought than that, but like any good hacker, [Yeo Kheng Meng] wanted to know how these devices worked.

After picking up a relatively advanced model that featured an LCD display capable of showing various stats such as detected voltage in addition to the standard trio of LEDs, he started by using some test leads to simulate various fault conditions to understand the basic principle behind its operation. The next step was to disassemble the unit, which is where things went briefly sideways — it wasn’t until [Yeo Kheng Meng] and a friend had nearly cut through the enclosure that they realized it wasn’t ultrasonically welded liked they assumed, and that the screws holding it together were actually hidden under a sticker. Oops.

The write-up includes some excellent PCB shots, and [Yeo Kheng Meng] was able to identify several components and ascertain their function. He was even able to find some datasheets, which isn’t always such an easy task with these low-cost devices. Unfortunately the MCU that controls the device’s more advanced features is locked away with a black epoxy blob, but he was able to come up with a schematic that explains the rather elegant logic behind the LED display.

This isn’t the first time [Yeo Kheng Meng] has taken apart an interesting piece of hardware for our viewing pleasure, and given the fine job he does of it, we hope it’s not the last either.

Homebrew Curve Tracer Competes With The Big Guns

July 22, 2022 by Al Williams 21 Comments

When we first saw the VBA curve tracer, we thought it might have something to do with Visual Basic for Applications. But it turns out it is a mash up of the names of the creators: [Paul Versteeg], [Bud Bennett], and [Mark Allie]. [Paul] designed an original prototype back in 2017. Since then, the project has grown and lessons were learned. The final curve tracer is pretty impressive in more ways than one.

If you’ve never used a curve tracer, they allow you to characterize components using their characteristic curve of voltage versus current. You use an oscilloscope as an output device. This instrument is often used by engineers trying to understand or match devices like diodes, transistors, or — in some cases — even tubes. So if you want to measure the collector-emitter breakdown voltage, for example, or the collector cutoff current, this is your go-to device. You can also match gains in circuits where that matters (for example, a push-pull circuit where two transistors amplify different parts of the same signal).

If you want to understand more about how it works, there are a series of blog posts covering the evolution of the device. You can also find the design files on GitHub. There is also a handy post showing many types of measurements you might want to make.

This is a good-looking project. We’ve seen it done on the cheap, but slowly. Or spend $15 and do better. We doubt any of these have high enough voltages to do most tubes, but they made the same basic instrument for tubes back in the 1950s.

Resulting tweezer assembly, with a 3D printed replacement case for both of the probes

Hackaday Prize 2022: Glue-Hindered Smart Tweezer Repair Involves A Rebuild

May 23, 2022 by Arya Voronova 1 Comment

[Dan Julio] owns a pair of Miniware multimeter tweezers, a nifty helper tool for all things SMD exploration. One day, he found them broken – unable to recognize any component between the two probes. He thought it could be a broken connection problem, and decided to take them apart. Presence of some screws on their case fooled him – in the end, it turned out that the case was glued together, and could only be opened destructively. For an entry in the “Reuse, Recycle, Revamp” round of 2022 Hackaday Prize, he tells us how he brought these tweezers back from the dead.

During the disassembly, he broke a custom flexible PCB, which wasn’t reassuring either. However, that was no reason to give up – he reverse-engineered the connections and the charging circuitry, then assembled parts of the broken tweezers together using a small generic protoboard as a base. Indeed, it was likely a broken connection between probes, because the reassembled tweezers worked!

Of course, having exposed PCBs wouldn’t do, and from the very start, assembling these tweezers back together was not an option. Instead, he developed a replacement case in OpenSCAD, bringing the tweezers back to life as his trusty tool – and still leaving repairability on the table. If you’re interested in the details, he goes more into how these tweezers are designed when it comes to charging and connectivity, and we recommend that you give his write-up a read!

We’ve been seeing smart tweezers around for over a decade now, from reviews and hacks of commercially made ones, to DIY chopstick-based and PCB-based ones. If you already own a pair of tweezers you’ve grown attached to, you can neatly retrofit them with a capacitance sensing function!

Building A Swiss Army Lab With Software Defined Instrumentation

April 29, 2022 by Tom Nardi 33 Comments

It’s a fair bet that anyone regularly reading Hackaday has a voltmeter within arm’s reach, and there’s a good chance an oscilloscope isn’t far behind. But beyond that, things get a little murky. We’re sure some of you have access to a proper lab full of high-end test gear, even if only during business hours, but most of us have to make do with the essentials due to cost and space constraints.

The ideal solution is a magical little box that could be whatever piece of instrumentation you needed at the time: some days it’s an oscilloscope, while others it’s a spectrum analyzer, or perhaps even a generic data logger. To simplify things the device wouldn’t have a physical display or controls of its own, instead, you could plug it into your computer and control it through software. This would not only make the unit smaller and cheaper, but allow for custom user interfaces to be created that precisely match what the user is trying to accomplish.

Wishful thinking? Not quite. As guest host Ben Nizette explained during the Software Defined Instrumentation Hack Chat, the dream of replacing a rack of test equipment with a cheap pocket-sized unit is much closer to reality than you may realize. While software defined instruments might not be suitable for all applications, the argument could be made that any capability the average student or hobbyist is likely to need or desire could be met by hardware that’s already on the market.

Ben is the Product Manager at Liquid Instruments, the company that produces the Moku line of multi-instruments. Specifically, he’s responsible for the Moku:Go, an entry-level device that’s specifically geared for the education and maker markets. The slim device doesn’t cost much more than a basic digital oscilloscope, but thanks to the magic of software defined instrumentation (SDi), it can stand in for eleven instruments — all more than performant enough for their target users.

So what’s the catch? As you might expect, that’s the first thing folks in the Chat wanted to know. According to Ben, the biggest drawback is that all of your instrumentation has to share the same analog front-end. To remain affordable, that means everything the unit can do is bound by the same fundamental “Speed Limit” — which on the Moku:Go is 30 MHz. Even on the company’s higher-end professional models, the maximum bandwidth is measured in hundreds of megahertz.

Additionally, SDI has traditionally been limited to the speed of the computer it was attached to. But the Moku hardware manages to sidestep this particular gotcha by running the software side of things on an internal FPGA. The downside is that some of the device’s functions, such as the data logger, can’t actually live stream the data to the connected computer. Users will have to wait until the measurements are complete before they pull the results off, though Ben says there’s enough internal memory to store months worth of high-resolution data.

Of course, as soon as this community hears there’s an FPGA on board, they want to know if they can get their hands on it. To that end, Ben says the Moku:Go will be supported by their “Cloud Compile” service in June. Already available for the Moku:Pro, the browser-based application allows you to upload your HDL to the Liquid Instruments servers so it can be built and optimized. This gives power users complete access to the Moku hardware so they can build and deploy their own custom features and tools that precisely match their needs without a separate development kit. Understanding that obsolescence is always a problem with a cloud solution, Ben says they’re also working with Xilinx to allow users to do builds on their own computers while still implementing the proprietary “secret sauce” that makes it a Moku.

It’s hard not to get excited about the promise of software defined instrumentation, especially with companies like Liquid Instruments and Red Pitaya bringing the cost of the hardware down to the point where students and hackers can afford it. We’d like to thank Ben Nizette for taking the time to talk with the community about what he’s been working on, especially given the considerable time difference between the Hackaday Command Center and Liquid’s Australian headquarters. Anyone who’s willing to jump online and chat about FPGAs and phasemeters before the sun comes up is AOK in our book.

The Hack Chat is a weekly online chat session hosted by leading experts from all corners of the hardware hacking universe. It’s a great way for hackers connect in a fun and informal way, but if you can’t make it live, these overview posts as well as the transcripts posted to Hackaday.io make sure you don’t miss out.

Open Source LXI Tools Free Us From Vendor Bloat

February 18, 2022 by Dave Rowntree 8 Comments

LXI, or LAN eXtensions for Instrumentation is a modern control standard for connecting electronics instrumentation which supports ethernet. It replaces the older GPIB standard, giving much better performance and lower cost of implementation. This is a good thing. [Martin Lund] has created the open source lxi-tools project which enables us to detach ourselves from the often bloated vendor tools usually required for talking LXI to your bench equipment. This is a partial rewrite of an earlier version of the tool, and now sports some rather nice features such as mDNS for instrument discovery, support for screen grabbing, and a LUA-based scripting backend. (API Link)

SCPI or Standard Commands for Programmable Instruments is the text-based language spoken by many instruments, allowing control and querying of an instrument. Just to be clear, SCPI is not at all a new thing, and older instruments that have GPIB or RS232 connectors, still could talk SCPI. lxi-tools is not for those. Some instruments can also be very picky about the formatting of commands, especially if they’re buggy, so the ability to interactively debug commands is very desirable. It is quite possible to make poor use of SCPI commands in your test script and end up with tests that just take far longer to execute that they need to. lxi-tools has a benchmarking tool too, which helps you to dig in and find out where all the time is going and make suitable adjustments.

We’ve not seen much about LXI on Hackaday, but we did cover using PyVISA for dealing with SCPI-over-GPIB in python. If you have an older instrument with GPIB and you don’t want to sell a internal organ to pay for a USB adaptor, here’s one you can make yourself.