Tool Hacks

2860 Articles

Your Multimeter Might Be Lying To You

April 10, 2023 by 33 Comments

Multimeters are indispensable tools when working on electronics. It’s almost impossible to build any but the most basic of circuits without one to test and troubleshoot potential issues, and they make possible a large array of measurement capabilities that are not easily performed otherwise. But when things start getting a little more complex it’s important to know their limitations, specifically around what they will tell you about circuits designed for high frequency. [watersstanton] explains in this video while troubleshooting an antenna circuit for ham radio.

The issue that often confuses people new to radio or other high-frequency projects revolves around the continuity testing function found on most multimeters. While useful for testing wiring and making sure connections are solid, they typically only test using DC. When applying AC to the same circuits, inductors start to offer higher impedance and capacitors lower impedance, up to the point that they become open and short circuits respectively. The same happens to transformers, but can also most antennas which often look like short circuits to ground at DC but can offer just enough impedance at their designed frequency to efficiently resonate and send out radio waves.

This can give some confusing readings, such as when testing to make sure that a RF connector isn’t shorted out after soldering it to a coaxial cable for example. If an antenna is connected to the other side, it’s possible a meter will show a short at DC which might indicate a flaw in the soldering of the connector if the user isn’t mindful of this high-frequency impedance. We actually featured a unique antenna design recently that’s built entirely on a PCB that would show this DC short but behaves surprisingly well when sending out WiFi signals.

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Busting Wireless ESD Wrist Straps With LTT And ElectroBOOM

April 10, 2023 by 28 Comments

Nobody likes getting zapped from an electrostatic discharge, no matter whether you’re a fragile ASIC or a bag-of-mostly-salty-water humanoid. To prevent this, ESD wrist straps and similar are essential tools, as they prevent the build-up of a charge on your humanoid’s skin, essentially like a very large electrolyte-filled capacitor. Yet you can buy wireless ESD straps everywhere that are supposed to somehow dissipate this charge into the ether, even though this would seem to undermine the laws of physics that make capacitors work.

In a practical experimentation and assorted hijinks video collaboration by [Linus] from Linus Tech Tips and [Mehdi Sadaghdar] from ElectroBOOM put these wireless ESD straps to the test, featuring [Mehdi]’s DIY Van de Graaff generator to charge [Linus] up. What is excellently demonstrated in this video is how effective a real ESD strap is, and how the ‘wireless’ version is just a scam that does absolutely nothing to dissipate the charge, being just a waste of a 1 MOhm resistor and what could have been a real ESD strap.

Also covered in the video are what the reason for the resistor in an ESD strap is, and why metal bracelet type ESD straps are not appropriate, for very good reasons.

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A Soft Soldering Jig For Hard Projects

April 5, 2023 by 20 Comments

We’ve seen some absolutely gorgeous freeform circuit sculptures. There’s a mystic quality to taking what has normally been hidden away for safety and reliability reasons and putting it on display for everyone to see. Of course, creating these unique circuit sculptures takes considerable time and effort. [Inne] created several silicone soldering jigs to help with these tricky joints.

While a vice or helping hands is crucial for many joints, when dealing with tiny SMD components and exacting angles, you need something a little more specialized. Double-sided tape is often recommended, but heat ruins the adhesive and SMD components like to stick to soldering iron tips. Since silicone tends to be heat resistant, it makes a decent material for soldering on. [Inne] uses a city analogy with the cups for soldering called plazas, each with a hole (called a manhole) leading to a foot-switch vacuum pump to keep parts in place. The OpenSCAD code is available on GitHub under a GPLv3 license. It generates a two-part mold that you can cast in A-8/A-15 silicone.

It’s a clever project that makes it far easier to assemble gorgeous circuit sculptures. We love the design and thought that went into it, particularly the naming scheme as we often find appropriately naming variables in OpenSCAD quickly becomes difficult.

The BLE Datalogging Scale Of A Thousand Uses

March 29, 2023 by 7 Comments

Whether you’re making coffee or beer or complex chemicals, weighing your ingredients carefully and tracking them is key to getting good results. [Tech Dregs] decided to build a logging scale that would work seamlessly with his smartphone, and shared the design on YouTube.

The design begins with a Greater Goods manual electronic scale, which was chosen for its convenient design and 750 gram load cell. Once cracked open, [Tech Dregs] pulled out the original PCB to replace it with his own. Only the original buttons are used, with an Seed Xiao ESP32-C3 replacing the scale’s original brains. The original LCD screen was swapped out for an OLED display, and it also got a rechargeable lithium battery for better usability.

The real value of the project, though, is its communication capability. It’s able to talk to an Android smartphone over Bluetooth Low Energy. Thanks to a custom app, [Tech Dregs] is able to log weight readings from the scale over time and even graph them live on the smartphone. As a demonstration, the scale is used to log the weight of a cup as it fills with a shot of coffee, which should serve [Tech Dregs] well in his coffee automation projects.

We’ve seen bathroom scales hacked before, too, with similar connectivity upgrades.

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Homebrew Tire Inflator Pushes The Limits Of PVC Construction

March 22, 2023 by 23 Comments

Let’s just clear something up right from the start with this one: there’s literally no reason to build your own tire inflator from scratch, especially when you can buy a perfectly serviceable one for not a lot of money. But that’s missing the point of this build entirely, and thinking that way risks passing up yet another fascinating build from PVC virtuoso [Vang Hà], which would be a shame

The chances are most of you will recall [Vang Hà]’s super-detailed working PVC model excavator, and while we’re tempted to say this simple air pump is a step toward more practical PVC builds, the fact remains that the excavator was a working model with a completely homebrew hydraulic system. As usual, PVC is the favored material, with sheet stock harvested from sections of flattened pipe. Only the simplest of tools are used, with a hand drill standing in for a lathe to make such precision components as the compressor piston. There are some great ideas here, like using Schrader tire valves as the intake and exhaust valves on the pump cylinder. And that’s not to mention the assembly tips, like making a hermetic seal between the metal valves and the PVC manifold by reaming out a hole with a heated drill bit.

We’re not sure how much abuse a plastic compressor like this will stand up to, but then again, we’ve seen some commercially available tire inflators with far, far less robust internals than this one.

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Vintage Tektronix Virtual Graticule

March 22, 2023 by 5 Comments

Oscilloscopes are great for measuring the time and voltage information of a signal. Some old scopes don’t have much in the way of markings on the CRT, although eventually, we started seeing scales that allowed you to count squares easily. Early scopes had marks on the glass or plastic over the CRT, but as [Vintage TEK Museum] points out, this meant for best accuracy, you had to look directly at the CRT. If you were at an angle horizontally or vertically, the position of the trace would appear to move concerning the lines on the screen. You can see the effect in the video below.

The simple solution was to mark directly into the phosphor, which minimized the effect. Before that was possible, [Bob Anderson] invented a clever solution, although Tektronix didn’t produce any scopes using it for some reason. The idea was the virtual oscilloscope graticule, and it was quite clever.

The idea was to put the graticule on a semi-reflective mirror. Looking through the assembly, you would actually see the trace and the reflection of the graticule in the mirror. The resulting image is perfectly aligned if the assembly is constructed properly. You can, at some angles, see both the front and reflected graticules.

According to the video, management was not impressed because someone other than [Anderson] showed a poor-quality prototype to them. By 1962, the graticule in the phosphor took over, and there was no need for [Anderson’s] clever invention.

These days, a graticule is just bits on the screen. Even if you roll your own.

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3D-Printed Shredder Eats Lettuce For Breakfast

March 19, 2023 by 15 Comments

Shredding things isn’t just good for efficiently and securely disposing of them. It’s also very fun, as well. [Joonas] of [Let’s Print] didn’t have a shredder, so set about 3D printing one of their very own.

The design apes that of the big metal trash shredders you’ve probably seen in videos all over the internet. They use a pair of counter-rotating drums with big teeth. As the drums turn, the teeth grab and pull objects into the gap between the drums, where they are duly torn apart into smaller pieces.

In this design, plastic drums are pressed into service as [Joonas] does not have a metal 3D printer. A brushed DC motor is used to drive the shredder. A large multi-stage gearbox is used to step down the motor’s output and provide plenty of torque to do the job.

The shredder gets tested with plenty of amusing garbage. Everything from old vegetables, to paper, and rock-hard old cheeseburgers are put through the machine. It does an able job in all cases, though obviously the plastic drums can’t handle the same kind of jobs as a proper metal shredder. Harder plastics and aluminium cans stall out the shredder, though. The gearbox also tends to strip gears on the tougher stuff. The basic theory is sound, but some upgrades could really make this thing shine.

Is it a device that will see a lot of practical use? Perhaps not. Is it a fun device that would be the star of your next hackerspace Show and Tell? Absolutely. Plus it might be a great way to get rid of lots of those unfinished projects that always clog up your storage areas, too! Video after the break.

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