picture showing the re-built scale with an extra blue box with electronics on the bottom of it. on the scale, there's a transparent food-grade plastic glass with measurement marks on the side.

Urine Flow Measurement Made Accessible With UroFlow

September 29, 2022 by Arya Voronova 21 Comments

If you’re dealing with a chronic illness, the ability to continuously monitor your symptoms is indispensable, helping you gain valuable insights into what makes your body tick – or, rather, mis-tick. However, for many illnesses, you need specialized equipment to monitor them, and it tends to be that you can only visit your doctor every so often. Thankfully, we hackers can figure out ways to monitor our conditions on our own. With a condition called BPH (Benign Prostate Hyperplasia), one of the ways to monitor it is taking measurements of urinary flow rate. Being able to take these measurements at home provides better insights, and, having found flow rate measurement devices to be prohibitively expensive to even rent, [Jerry Smith] set out to build his own.

This build is truly designed to be reproducible for anyone who needs such a device. Jerry has intricately documented the project and its inner workings – the 31-page document contains full build instructions, BOM for ordering, PCB description and pinout diagrams, calibration and validation instructions, and even software flowcharts; the GitHub repo has everything else you might need. We’re pleasantly surprised – this amount of documentation isn’t typically seen in hacker projects, and is even more valuable considering that this is a medical device that other hackers in need will want to reproduce.

For the hardware, [Jerry] took a small digital scale of a certain model and reused its load cell-based weighing mechanism using an HX711 amplifier, replacing the screen and adding an extra box for control electronics. With an Arduino MKR1010 as brains of the operation, the hardware’s there to log flow data, initially recorded onto the SD card, with WiFi connectivity to transfer the data to a computer for plotting; a DS3234 RTC breakout helps keep track of the time, and a custom PCB ties all of these together. All of these things are easy to put together, in no small part due to the extensive instructions provided.

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A weighing scale with a moving-coil meter as a display

Hackaday Prize 2022: Arduino-Powered Weighing Scale Has A Real Analog Display

July 25, 2022 by Robin Kearey 3 Comments

Digital displays are useful for quick and accurate readout, but lots of people prefer the physical motion of a needle moving along a dial. For instance, many smartwatch users choose an analog face to show the time, and modern cars with digital dashboards often default to showing an analog speedometer. Following this trend, [Miro Pavleski] built a digital weighing scale with an analog display that not only looks neat, but also serves as a good demonstration of the way that modern scales work.

Inside, the device is built up like a typical electronic scale: the heart of the instrument is a load cell that supports the platform and bends in proportion to the weight applied. This bending motion is sensed by a set of strain gauges wired up in a Wheatstone bridge configuration. An HX711 readout chip measures the resulting voltage and converts it to a digital code that is sent to a microcontroller, in this case an Arduino Nano.

Whereas a typical scale would then simply show the resulting number on an LCD display, [Mirko] decided to use a moving coil meter driven by the Arduino’s analog output. That meter was originally designed to show currents, so [Mirko] printed a new background image using kilograms instead.

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Raspberry Pi Test Stand Tells You Which Glues To Use

April 7, 2022 by Dan Maloney 6 Comments

Not all glues are created equal; or rather, not every glue is good for every application. But how is one to know which glue to use in which kinds of joints? The answer to that is not always clear, but solid numbers on the comparative strength of different glues are a great place to start.

To quantify what can ordinarily be a somewhat subjective process, there’s probably no one better than woodworker and hacker [Matthias Wandel], equipped as he is with his DIY strength-tester. Using its stepper-driven power to blast apart glued lap joints, [Matthias] measured the yield point of the various adhesives using a strain gauge connected to a Raspberry Pi.

His first round of tests had some interesting results, including the usually vaunted construction adhesive ending up in a distant last place. Also performing poorly, at least relative to its reputation and the mess it can cause, was the polyurethane-based Gorilla Glue. A surprise standout in overall strength was hot glue, although that seemed to have a sort of plastic yield mode. Ever the careful empiricist, [Matthias] repeated his tests using hardwoods, with remarkably different results; it seems that glues really perform better with denser wood. He also repeated a few tests to make sure every adhesive got a fair shake. Check out the video below for the final results.

It’s always good to see experiments like this that put what we often take for granted to the test. [John] over at the Project Farm channel on YouTube does this kind of stuff too, and even did a head-to-head test of epoxy adhesives.

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A Lego cup holder with a glass of water and electronics on a breadboard

LEGO Cup Holder Helps You To Stay Hydrated

January 4, 2022 by Robin Kearey 11 Comments

Eat more fruit, exercise more, drink more fluids; early January is traditionally the time to implement New Year’s resolutions. Most of the common ones simply require willpower, but if it’s staying hydrated that you’re targeting, then some help is available. [Pepijn de Vos] designed a LEGO cup holder and an accompanying desktop app that tell you exactly how much water you’ve had so far, making it easier to get to those eight glasses a day.

The basic idea is simple: the cup holder contains a load cell that senses the weight of your drinking vessel. If the weight decreases, then a message is sent to your PC detailing the amount lost. If the weight increases, then the glass must have been refilled and the previous weight is disregarded. This way, the app simply needs to add up all the amounts reported, without having to compensate for the weight of the empty glass.

The tricky bit was integrating a load cell into the LEGO structure. It required some fiddling with Flex System hoses to ensure the platform’s weight rested only on the load cell, while still being stable enough to safely hold a full glass of water. The load cell is read out through an amplifier and A/D converter, while the USB communication is handled by a Teensy 3.

[Pepijn] modified an existing GNOME desktop widget to display a cup icon and the total volume consumed, which seems to work pretty smoothly judging from the video embedded below. All the code and even a complete set of LEGO build instructions are available on the project’s Github page. If simply monitoring your fluid intake isn’t enough of a nudge for you, then check out this device that floods your desk if you don’t drink enough.

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Prusa XL Goes Big, But That’s Only Half The Story

November 29, 2021 by Tom Nardi 44 Comments

For a few years now it’s been an open secret that Prusa Research was working on a larger printer named, imaginatively enough, the Prusa XL. Positioned at the opposite end of their product spectrum from the wildly popular Prusa Mini, this upper-tier machine would be for serious hobbyists or small companies that need to print single-part objects that were too large for their flagship i3 MK3S+ printer. Unfortunately, the global COVID-19 pandemic made it difficult for the Czech company to focus on bringing a new product to market, to the point that some had begun to wonder if we’d ever see this mythical machine.

But now, finally, the wait is over. Or perhaps, it’s just beginning. That’s because while Prusa Research has officially announced their new XL model and opened preorders for the $1,999+ USD printer, it’s not expected to ship until at least the second quarter of 2022. That’s already a pretty substantial lead time, but given Prusa’s track record when it comes to product launches, we wouldn’t be surprised if early adopters don’t start seeing their machines until this time next year.

So what do you get for your money? Well, not an over-sized Prusa i3, that’s for sure. While many had speculated the XL would simply be a larger version of the company’s popular open source printer with a few modern niceties like a 32-bit control board sprinkled in, the reality is something else entirely. While the high purchase price and ponderous dimensions of the new machine might make it a tough sell for many in the hacker and maker communities, there’s little question that the technical improvements and innovations built into the Prusa XL provide a glimpse of the future for the desktop 3D printer market as a whole.

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Finding The Right Hack Is Half The Battle

September 18, 2021 by Elliot Williams 25 Comments

Sometimes you just get lucky. I had a project on my list for a long time, and it was one that I had been putting off for a few months now because I loathed one part of what it entailed — sensitive, high-accuracy analog measurement. And then, out of the blue I stumbled on exactly the right trick, and my problems vanished in thin air. Thanks, Internet of Hackers!

The project in question is a low-vacuum regulator for “bagging” fiberglass layups. What I needed was some way to read a pressure sensor and turn on and off a vacuum pump accordingly. The industry-standard vacuum gauges are neat devices, essentially a tiny little strain gauge on a membrane between the vacuum side and the atmosphere side, in a package the size of a dime. (That it’s a strain gauge is foreshadowing, but I didn’t know that at the time.) I bought one for $15 ages ago, and it sat on my desk, awaiting its analog circuitry.

See, the MPX2100 runs on 12 V and puts out a signal around 40 mV on top of a 6 V offset. That voltage level is inconvenient for modern 3.3 V microcontroller ADCs, and the resolution would get clobbered by the 6 V signal if I just put a voltage divider on it. This meant whipping together some kind of instrument amplifier circuit to null out the 6 V and amplify the 40 mV for the ADC. The circuits I found online all called for 1% resistors in values I didn’t have, and mildly special op-amps. No fun, for me at least. So there it sat.

Picture of sketchy-looking vacuum apparatus. — Cut the blue wire or the red wire? HX711 module and pressure sensor on the left.

Until I ran into this project that machetes through the analog jungle with one part, and it happened to be one I had on hand. A vacuum pressure sensor is a strain gauge, set up like a Wheatstone bridge, just like you would use for weighing something with a load cell. The solution? A load-cell ADC chip, the HX711, found in every cheap scale or online for under a buck. The only other trick was finding a low-voltage pressure sensor to work with it, but that turns out to be easy as well, and I had one delivered in two days.

In all, this project took months of foot-dragging, but only a few clicks and five minutes of soldering once I got the right idea. The industrial applications and manufacturers’ app notes all make sense if you are making hundreds or millions of these devices, where the one-time cost of prototyping up the hard bits gets amortized, but the hacker solution of using a weight-scale chip was just the ticket for a one-off. That just goes to show how useful sharing our tips and tricks can be — you won’t get this from the industry. So send us your success stories, and your useful failures too, and Read More Hackaday!

3D Printering: Is Hassle-Free Bed Leveling Finally Here?

August 30, 2021 by Donald Papp 72 Comments

3D printers have come a long way over the past several years, but the process of bed leveling remains a pain point. Let’s take a look at the different ways the problem has been tackled, and whether recent developments have succeeded in automating away the hassle.

Anycubic Vyper 3D printer, front view — Anycubic Vyper, with an auto-leveling feature we decided to take a closer look at.

Bed leveling and first layer calibration tends to trip up novices because getting it right requires experience and judgment calls, and getting it wrong means failed prints. These are things 3D printer operators learn to handle with time and experience, but they are still largely manual processes that are often discussed in ways that sound more like an art than anything else. Little wonder that there have been plenty of attempts to simplify the whole process.

Some consumer 3D printers are taking a new approach to bed leveling and first layer calibration, and one of those printers is the Anycubic Vyper, which offers a one-touch solution for novices and experienced users alike. We accepted Anycubic’s offer of a sample printer specifically to examine this new leveling approach, so let’s take a look at the latest in trying to automate away the sometimes stubborn task of 3D printer bed leveling.

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