[mircemk] built a slick-looking LED tester with a couple handy functions built in. Not only can one select a target current to put through an LED, but by providing a target voltage, the system will automatically calculate the necessary series resistor. If for example the LED is destined for 14 V, this device will not only show how the LED looks at the chosen current, but will calculate the required resistor to get the same results on a 14 V system.

The buttons on the left control the target current and the voltage of the destination system. Once an LED is connected it will light up and the display indicates the LED’s forward voltage, the LED current, and the calculated series resistor value to obtain the same result at the selected target voltage. It’s a handy way to empirically dial in LED brightness values without needing to actually set up any particular test environment.

On the inside there’s little more than a handful of passive components, an Arduino, an LCD display, and a few buttons. This kind of tool reminds us of the highly clever component testers that hit the hobbyist scene years ago, showing what kind of advanced tricks a modern microcontroller is capable of with the right programming. (Here’s a look at how those work, if you’re interested in some deeper details.)

[mircemk] demonstrates his tool in the video, embedded below. We particularly like the attention he paid to the enclosure, giving it a very functional layout. It goes to show that when designing something, it’s never too early to consider enclosure and UI layout.

Spare a moment’s pity for the process engineer, whose job it is to keep industrial automation running no matter what. These poor souls seem to be forever on call, fielding panicked requests to come to the factory floor whenever the line goes down. Day or night, weekends, vacations, whatever — when it breaks, the process engineer jumps.

The pressures of such a gig can be enormous, and seem to have weighed on [Tom Goff] enough that he spent a weekend building a junk bin analog signal generator to replace a loop calibrator that he misplaced. Two process control signaling schemes were to be supported — the 0 to 10 VDC analog signal, and the venerable 4-20 mA current loop. All that’s needed for both outputs is an Arduino and an LM358 dual op-amp, plus a few support components. The 0-10 V signal starts as a PWM output from the Arduino, with its 0-5 V average amplified by one of the op-amps set up as a non-inverting amp with a gain of 2. With a little filtering, the voltage output is pretty stable, and swings nicely through the desired range — see the video below for that.

The current loop output is only slightly more complicated. An identical circuit on a separate Arduino output generates the same 10 V max output, but a code change limits the low end of the range to 1 V. This output of the op-amp is fed through a 500-Ω trimmer pot, and the magic of Ohm’s Law results in a 4-20 mA current. The circuit lives on a piece of perf board in a small enclosure and does the job it was built for — nothing fancy needed.

And spoiler alert: [Tom] found the missing loop calibrator — after he built this, of course. Isn’t that always the way?

If you spend much time around industrial processes, you may have seen a vibrating bowl feeder at work. It’s a clever but simple machine that takes an unruly pile of screws or nuts and bolts, and delivers them in a line the correct way up. They do this by shaking the pile of fasteners in a specific way — a spiral motion which encourages them to work to the edge of the pile and align themselves on a spiral track which leads to a dispenser. It’s a machine [Fraens] has made from 3D printed parts, and as he explains in the video below the break, there’s more to this than meets the eye.

The basic form of the machine has a weighted base and an upper bowl on three angled springs. Between the two is an electromagnet, which provides the force for the vibration. The electromagnet needed to be driven with a sine wave which he makes with an Arduino and delivers as PWM via an H-bridge, but the meat of this project comes in balancing the force and frequency with the stiffness of the springs. He shows us the enormous pile of test prints made before the final result was achieved, and it’s a testament to the amount of work put into this project. The final sequence of a variety of objects making the march round the spiral is pure theatre, but we can see his evident satisfaction in a job well done.

Oddly this isn’t the first bowl feeder we’ve seen, though it may be one of the most accomplished. We particularly like this tiny example for SMD parts.

Most of us are content to get our semiconductors from the usual sources, happily abstracting away the complexity locked within those little epoxy blobs. But eventually, you might get the itch to roll your own semiconductors, in which case you’ll need to start gearing up. And one of the first tools you’ll need is likely to be something like this DIY tube furnace.

For the uninitiated, [ProjectsInFlight] helpfully explains in the video below just what a tube furnace is and why you’d need one to start working with semiconductors. Perhaps unsurprisingly, a tube furnace is just a tube that gets really, really hot — like 1,200° C. In addition to the extreme heat, commercial furnaces are often set up to seal off the ends of the tube to create specific conditions within, such as an inert gas atmosphere or even a vacuum. The combination of heat and atmospheric control allows the budding fabricator to transform silicon wafers using chemical and physical processes.

[ProjectsInFlight]’s tube furnace started with a length of heat-resistant quartz glass tubing and a small tub of sodium silicate refractory cement, from the plumbing section of any home store. The tube was given a thin coat of cement and dried in a low oven before wrapping it with nichrome wire. The wrapped tube got another, thicker layer of silicate cement and an insulating wrap of alumina ceramic wool before applying power to cure everything at 1,000° C. The cured tube then went into a custom-built sheet steel enclosure with plenty of extra insulation, along with an Arduino and a solid-state relay to control the furnace. The video below concludes with testing the furnace by growing a silicon dioxide coating on a scrap of silicon wafer. This was helped along by the injection of a few whisps of water vapor while ramping the furnace temperature up, and the results are easily visible.

[ProjectsInFlight] still needs to add seals to the tube to control the atmosphere in there, an upgrade we’ll be on the lookout for. It’s already a great start, although it might take a while to catch up to our friend [Sam Zeloof].

There was a time not that long ago when every tool was cordless. But now, cordless power tools have proliferated to the point where the mere thought of using a plain old wrist-twisting screwdriver is enough to trigger a bout of sympathetic repetitive injury. And the only thing worse than that is to discover that the batteries for your tools are all dead.

As [Lance] from the “Sparks and Code” channel freely admits, the fact that his impressive collection of batteries is always dead is entirely his fault, and that’s what inspired his automatic battery charging robot. The design is pretty clever; depleted batteries go into a hopper, under which is a 3D-printed sled. Batteries drop down into the sled, which runs the battery out from under the hopper to the charging station, which is just the guts of an old manual charger attached to a lead screw to adjust the height of the charging terminals for different size batteries. When the battery is charged, the sled pushes it a little further into an outfeed hopper before going back to get another battery from the infeed side.

Of course, that all vastly understates the amount of work [Lance] had to put into this. He suffered through a lot of “integration hell” problems, like getting the charger properly connected to the Arduino running the automation. But with a lot of tweaking, he can now just dump in a bunch of depleted packs and let the battery bot handle everything. The video after the break shows all the gory details.

Of course, there’s another completely different and much simpler solution to the dead battery problem.

The team at the Berlin-based Studio HILO has been working on ideas and tools around developing a more open approach to small-scale textile production environments. Leveraging open-source platforms and tools, the team has come up with a simple open hardware spinning machine that can be used for interactive yarn production, right on the desktop. The frame is built with 3030 profile aluminium extrusions, with a handful of 3D printed, and a smidge of laser cut parts. Motion is thanks to, you guessed it, NEMA 17 stepper motors and the once ubiquitous Arduino Mega 2560 plus RAMPS 1.4 combination that many people will be very familiar with.

The project really shines on the documentation side of things, with the project GitLab positively dripping with well-organised information. One minor niggle is that you’ll need access to a polyjet or very accurate multi-material 3D printer to run off the drive wheel and the associated trailing wheel. We’re sure there’s a simple enough way to do it without those tools, for those sufficiently motivated.

We liked the use of Arduino for the firmware, keeping things simple, and in the same vein, Processing for the user interface. That makes sending values from the on-screen slider controls over the USB a piece of cake. Processing doesn’t seem to pop up on these pages too often, which is a shame as it’s a great tool to have at one’s disposal. On the subject of the user interface, it looks like for now only basic parameters can be tweaked on the fly, with some more subtle parameters needing fixing at firmware compilation time. With a bit more time, we’re sure the project will flesh out a bit more, and that area will be improved.

Of course, if you only have raw fibers, that are not appropriately aligned, you need a carder, like this one maybe?

Thanks [Daniel] for the tip!

The one thing that separates the pros on Twitch from the dilettantes is the production values. It’s all about the smooth transitions, and you’ll never catch the big names fiddling with dodgy software mid-stream. The key to achieving this is by having a streamdeck to help control your setup, like this straightforward design from [Electronoobs]. (Video, embedded below.)

The build relies on an Arduino Micro, which is a microcontroller board perfectly equipped to acting as a USB macro keyboard. It’s paired with a Nextion LCD touchscreen that displays buttons for various stream control features, like displaying a “Be Right Back” screen or cuing up video clips. The build also features bigger regular buttons for important quick-access features like muting a mic. It’s all wrapped up in a 3D printed housing, with some addressable RGB LEDs running off another Arduino to add some pizazz. The neat trick is that the build sends keycodes for F13-F24, which allows for the streamdeck’s hotkeys to avoid conflicting with any other software using conventional keyboard hotkeys.

It’s a useful tool that would be of use to anyone streaming on Twitch or other platforms. Alternatively, you could repurpose an old phone to do a similar job. Video after the break.

With surface-mount components quickly becoming the norm, even for homebrew hardware, the resistor color-code can sometimes feel a bit old-hat. However, anybody who has ever tried to identify a random through-hole resistor from a pile of assorted values will know that it’s still a handy skill to have up your sleeve. With this in mind, [j] decided to super-size the color-code with “The Great Resistor”.

At the heart of the project is an Arduino Nano clone and a potential divider that measures the resistance of the test resistor against a known fixed value. Using the 16-bit ADC, the range of measurable values is theoretically 0 Ω to 15 MΩ, but there are some remaining issues with electrical noise that currently limit the practical range to between 100 Ω and 2 MΩ.

[j] is measuring the supply voltage to help counteract the noise, but intends to move to an oversampling/averaging method to improve the results in the next iteration.

The measured value is shown on the OLED display at the front, and in resistor color-code on an enormous symbolic resistor lit by WS2812 RGB LEDs behind.

Precision aside, the project looks very impressive and we like the way the giant resistor has been constructed. It would look great at a science show or a demonstration. We’re sure that the noise issues can be ironed out, and we’d encourage any readers with experience in this area to offer [j] some tips in the comments below. There’s a video after the break of The Great Resistor being put through its paces!

If you want to know more about the history of the resistor color code bands, then we have you covered.  Alternatively, how about reading the color code directly with computer vision?

The hacking life is not without its challenges, and chief among these is the tendency to always be in acquisition mode. When we come across a great deal on bulk equipment, or see a chance to rescue some obscure gear from the e-waste stream, we generally pounce on it, regardless of the advisability.

We imagine this is why [Nathan] ended up with a hoard of PS/2 keyboards. Seriously, there are like thousands of the things. And rather than lug a computer to them for testing, [Nathan] put together this handy Arduino-based portable tester to see which keyboards still have some life left in them. The video below goes into detail on the build, but the basics are pretty simple — an Arduino, a 16×2 LCD display, and a few bits and bobs to run it off a LiPo pack and charge it up. Plus, of course, a PS/2 jack to plug in a keyboard and power it up. Interestingly, the 16×2 display is an old Parallax unit, from the days when RadioShack still existed and sold their stuff. That required a little effort to get it working with the Arduino, but in the end it works like a charm — plug in a keyboard and whatever you type shows up on the screen.

Of course, it’s hard to look at something like this, and that mountain of keyboards in the background, and not scheme up ways to really automate the whole test process. Perhaps an old 3D printer with a stylus mounted where the hot end would go could press each key in turn while the tester output is recorded — something like this Wordle-bot, but on a keyboard scale. That kind of goes against [Nathan]’s portability goal, but it’s still fun to think about.

[Sebastian] and [Stefan Shütz] had a ISEL EP1090 CNC machine at home, sitting unused, and they decided to bring it to life. With pretty good mechanical specs, this CNC looked promising – alas, it was severely constrained by its controller. The built-in CPU’s software was severely outdated, had subpar algorithms for motor driving programmed in, and communication with the CNC was limited because the proprietary ISEL communications protocol that isn’t spoken by other devices.The two brothers removed the CPU from its PLCC socket, and went on to wiring a grbl-fueled Arduino into the controller box.

They reverse-engineered the motor driver connections – those go through a 74HC245 buffer between the original CPU and the drivers. Initially, they put an Arduino inside the control box of the CNC and it fit nicely, but it turned out the Arduino’s CPU would restart every time the spindle spun up – apparently, EMC would rear its head. So, they placed the Arduino out of the box, and used two CAT7 cables to wire up the motor and endstop signals to it.

For tapping into these signals, they took the 74HC245 out of its socket, and made an interposer from two small protoboards and some pin headers – letting them connect to the STEP and DIR lines without soldering wires into the original PCB. There’s extensive documentation, GRBL settings, and more pictures in their GitHub repo, too – in case you have a similar CNC and would like to learn about upgrading its controller board!

After this remake, the CNC starts up without hassles. Now, the brothers shall CNC on! Often, making an old CNC machine work is indeed that easy, and old controller retrofits have been a staple of ours. You can indeed use an Arduino, one of the various pre-made controller boards like Gerbil or TinyG, or even a Raspberry Pi – whatever helps you bridge the divide between you and a piece of desktop machinery you ought to start tinkering with.