Putting Cheap Motorcycle Tachometers To Work

January 18, 2025 by Tom Nardi 15 Comments

With so much data being thrown at our eyeballs these days, it’s worryingly easy for the actually important stuff to slip by occasionally. So when [Liam Jackson] wanted a way to visualize the number of test failures popping up in the continuous integration system at work, he went with a novel but effective solution — universal motorcycle tachometers.

It turns out these little gauges can be had for under $10 a piece from the usual overseas retailers, and are very easy to drive with a microcontroller. As [Liam] explains, all you need to do other than providing them with 12 volts, is feed them a PWM signal. Even though the gauges are designed for a 12 V system, they apparently don’t have any problem responding to the 5 V logic level from the Arduino’s pins.

As for the frequency he says that 1,000 RPM corresponds to 16.66 Hz, so you can just multiply up from there to show whatever number you wish. That said, [Liam] warns that the gauges draw several hundred milliamps once the needle gets into the two digit range, so keep that in mind. Conveniently, those number happen to be in red anyway…

For his particular application, [Liam] put three of the gauges together to create a very handsome dashboard. If you want to recreate his setup exactly he’s made the STLs available for the gauge cluster housing. Note the small OLED at the center, this offers a way to show a bit more context than the three analog gauges alone can express, especially if you’ve got an application where you might be switching between multiple data sources.

Over the years we’ve seen several projects that repurposed analog gauges of various types, often for showing computer performance, but they generally involved having to drive the galvanometers directly. That these tachometers can simply be fed a simple digital signal should make implementing them into your project much easier.

Learn New Tools, Or Hone Your Skill With The Old?

January 18, 2025 by Elliot Williams 41 Comments

Buried in a talk on AI from an artist who is doing cutting-edge video work was the following nugget that entirely sums up the zeitgeist: “The tools are changing so fast that artists can’t keep up with them, let alone master them, before everyone is on to the next.” And while you might think that this concern is only relevant to those who have to stay on the crest of the hype wave, the deeper question resounds with every hacker.

When was the last time you changed PCB layout software or refreshed your operating system? What other tools do you use in your work or your extra-curricular projects, and how long have you been using them? Are you still designing your analog front-ends with LM358s, or have you looked around to see that technology has moved on since the 1970s? “OMG, you’re still using ST32F103s?”

It’s not a simple question, and there are no good answers. Proficiency with a tool, like for instance the audio editor with which I crank out the podcast every week, only comes through practice. And practice simply takes time and effort. When you put your time in on a tool, it really is an investment in that it helps you get better. But what about that newer, better tool out there?

Some of the reluctance to update is certainly sunk-cost fallacy, after all you put so much sweat and tears into the current tool, but there is also a real cost to overcome to learn the new hotness, and that’s no fallacy. If you’re always trying to learn a new way of doing something, you’re never going to get good at doing something, and that’s the lament of our artist friend. Honing your craft requires focus. You won’t know the odd feature set of that next microcontroller as well as you do the old faithful – without sitting down and reading the datasheet and doing a couple finger-stretching projects first.

Striking the optimal balance here is hard. On a per-project basis, staying with your good old tool or swapping to the new hotness is a binary choice, but across your projects, you can do some of each. Maybe it makes sense to budget some of your hacking time into learning new tools? How about ten percent? What do you think?

JTAG & SWD Debugging On The Pi Pico

January 18, 2025 by Tom Nardi 19 Comments

[Surya Chilukuri] writes in to share JTAGprobe — a fork of the official Raspberry Pi debugprobe firmware that lets you use the low-cost microcontroller development board for JTAG and SWD debugging just by flashing the provided firmware image.

We’ve seen similar projects in the past, but they’ve required some additional code running on the computer to bridge the gap between the Pico and your debugging software of choice. But [Surya] says this project works out of the box with common tools such as OpenOCD and pyOCD.

As we’ve cautioned previously, remember that the Pi Pico is only a 3.3 V device. JTAG and SWD don’t have set voltages, so in the wild you could run into logic levels from 1.2 V all the way to 5.5 V. While being able to use a bare Pico as a debugger is a neat trick, adding in a level shifter would be a wise precaution.

Looking to get even more use out of those Pi Picos you’ve got in the parts bin? How about using it to sniff USB?

A PDA From An ESP32

January 18, 2025 by Jenny List 11 Comments

The ESP32 series of microcontrollers have been with us for quite a few years now and appeared in both Tensilica and RISC-V variants, both of which deliver an inexpensive and powerful device. It’s thus shown up in quite a few handheld computers, whether they be conference badges or standalone devices, and this is definitely a field in which these chips have more to give. We’re pleased then to see this e-ink PDA from [ashtf8], which we think raises the bar on this type of device.

At its heart is an ESP32-S3, on the back side of a QWERTY keyboard PCB, and for a display it has an e-ink screen. To get over the annoying e-ink refresh when typing text it uses a hybrid of e-ink and OLED, with a small OLED holding the current line which can be periodically sent to the e-ink. Perhaps the nicest thing about the hardware though is the clear resin printed clamshell case, and a hand-cast silicone membrane for the keyboard. That has always been a part considered difficult to produce, and here he is making one from scratch. Take a look at the video below the break.

Software-wise it has a range of apps with more promised, but even as it stands it looks useful enough to work with. If that’s not enough, then perhaps an ESP32 operating system would help.

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A Field Expedient Welder Only MacGyver Could Love

January 17, 2025 by Dan Maloney 42 Comments

If you needed to weld something in a pinch, what’s the minimum complement of equipment you could get away with? In [Professor Bardal]’s case, it’s a couple of motorcycle batteries and a roll of flux-core wire, and not much else.

We suspect this one is going to elicit quite a few comments, not least by the welding fans who no doubt will be triggered by just about everything in the video below, especially by characterizing this as MIG welding; it’s FCAW, or flux-core arc welding. But it bears some superficial similarities to MIG, at least insofar as there’s a consumable wire electrode through which a high-current DC supply flows, creating enough heat to melt it and the base metal. In this case, the current is provided by a pair of 12-volt motorcycle batteries hooked together in series. There’s also a torch of sorts — a short length of copper capillary tubing with a 1-mm inside diameter clamped in the jaws of a stick welder stinger, or a pair of locking pliers if you’re really in a pinch. The torch is connected to the negative terminal on the battery with a jumper cable, and the positive terminal is connected to the workpiece.

To create the weld, a piece of 0.8-mm flux-core welding wire is threaded through the capillary and into the joint, and fed by hand as it’s consumed. It’s awkward and awful, but it works. Of course, there’s no control over amperage as there would be with a legit welding machine, which would make it hard to adapt this method to different materials. Weld quality appears poor, too. But we suspect that if you were in a position to need a welder like this, you wouldn’t really care about any of that.

Fabricobbled welding rigs seem to be [Professor Bardal]’s thing — witness this much more professional MIG welder, complete with a baking soda and vinegar shielding gas generator.

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No Crystal Earpiece? No Problem!

January 17, 2025 by Jenny List 10 Comments

A staple of starting off in electronics ion years past was the crystal set radio, an extremely simple AM radio receiver with little more than a tuned circuit and a point contact diode as its components. Point contact diodes have become difficult to find but can be replaced with a cats whisker type detector, but what about listening to the resulting audio? These circuits require a very high impedance headphone, which was often supplied by a piezoelectric crystal earpiece. [Tsbrownie] takes a moment to build a replacement for this increasingly hard to find part.

It shouldn’t have come as a surprise, but we were still slightly taken aback to discover that inside these earpieces lies the ubiquitous piezoelectric buzzer element. Thus given a 3D-printed shell to replace the one on the original, it’s a relatively simple task to twist up a set of wires and solder them on. The result is given a test, and found to perform just as well as the real thing, in fact a little louder.

In one sense this is such a simple job, but in another it opens up something non-obvious for anyone who needs a high impedance earpiece. The days of the crystal radios and rudimentary transistor hearing aids these parts were once the main target for may both have passed, but just in case there’s any need for one elsewhere, now we can fill it. Take a look at the video, below the break.

Fancy trying a crystal radio? We’ve got you covered.

Continue reading “No Crystal Earpiece? No Problem!” →

Trinteract, a small space mouse, operating in Blender.

Trinteract Mini Space Mouse Does It In 3D

January 17, 2025 by Kristina Panos 16 Comments

We’re not sure how we managed to miss this one, but better late than never, right? This is Trinteract, a 3-DOF input device that’s both open-source and Arduino compatible. There’s even a neat 3D-printed clip to add it to the side of your laptop.

Imagine navigating 2D and 3D environments, or flying around in Minecraft with ease. [Görkem]’s custom PCB features a Hall effect sensor which picks up readings from the magnet embedded in the bottom of the joystick. You can use any magnetic object as input. In the video below the break, [Görkem] shows a 3D-printed sphere with a disc magnet trapped inside as an alternative. The super-neat part is that the thing moves around entirely on flexures. You know how much we love flexures around here.

[Görkem] has written up a fantastic guide for those who must have one of their own. As a bonus, the guide details the background and thought process behind the design, which we love to see.

Don’t like magnets? This space mouse uses an accelerometer and a spring.

Continue reading “Trinteract Mini Space Mouse Does It In 3D” →