Hydraulic Press Channel Puts Nuts To The Test

October 19, 2022 by Al Williams 18 Comments

Have you ever wondered how many threads a nut needs to be secure? [Hydraulic Press Channel] decided to find out, using some large hardware and a hydraulic press. The method was simple. He took a standard nut and cut the center out of it to have nuts with fewer threads than the full nut. Then it was on to the hydraulic press.

As you might expect, a single-thread nut gave way pretty quickly at about 10,000 kg. Adding threads, of course, helps. No real surprise, but it is nice to see actual characterization with real numbers. It is also interesting to watch metal hardware bend like cardboard at these enormous pressures.

In the end, he removed threads from the bolts to get a better test and got some surprising results. Examining the failure modes is also interesting.

Honestly, we aren’t sure how valid some of the results were, but it was interesting watching the thread stripping and the catastrophic failures of the samples in the press. It seems like to do this right, you need to try a variety of assemblies and maybe even use different materials to see if all the data fit with the change in the number of threads. We expect the shape of the threads also makes a difference.

Still, an interesting video. We always enjoy seeing data generated to test theories and assumptions. We think of bolts and things as pretty simple, but there’s a surprising amount of technology that goes into their design and construction.

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Adding A Third Wheel (And Speed Boost) To An Electric Scooter

September 24, 2022 by Donald Papp 7 Comments

The story of how [Tony]’s three-wheeled electric scooter came to be has a beginning that may sound familiar. One day, he was browsing overseas resellers and came across a new part, followed immediately by a visit from the Good Ideas Fairy. That’s what led him to upgrade his DIY electric scooter to three wheels last year, giving it a nice speed boost in the process!

The part [Tony] ran across was a dual brushless drive unit for motorizing a mountain board. Mountain boards are a type of off-road skateboard, and this unit provided two powered wheels in a single handy package. [Tony] ended up removing the rear wheel from his electric scooter and replacing it with the powered mountain board assembly.

He also made his own Arduino-based interface to the controller that provides separate throttle and braking inputs, because the traditional twist-throttle of a scooter wasn’t really keeping up with what the new (and more powerful) scooter could do. After wiring everything up with a battery, the three-wheeled electric scooter was born. It’s even got headlights!

[Tony]’s no stranger to making his own electric scooters, and the fact that parts are easily available puts this kind of vehicular experimentation into nearly anybody’s hands. So if you’re finding yourself inspired, why not order some stuff, bolt that stuff together, and go for a ride where the only limitation is personal courage?

CMOS Oscillator Circuit Gets An Eatable Input

September 24, 2022 by Lee Wilkins 9 Comments

In interaction designer [Leonardo Amico]’s work Processing Decay, lettuce is used as an input to produce sound as an element within a CMOS circuit.

We’ve all seen lemons and potatoes doubling in science-fairs as edible batteries, but lettuce is something else. [Leandro]’s circuit uses alligator clips to insert lettuce into oscillators in this audio generating circuit — we think they’re behaving like resistors. Without refrigeration, the resistance of the lettuce changes, and so does the oscillation in the circuit. In a matter of hours, days, and weeks the cells degrades slowly, modulating the system and its sonic output. What a way to make music!

This hack isn’t the freshest — the video dates from nine years ago — but this is the first lettuce circuit we’ve seen. Of course, we love other food hacks like these multi-wavelength lasers used to cook 3D-printed chicken, or maybe the circuit can make use of this neural net detecting fruit ripeness.

Minimal Tic Tac Toe Business Card

September 24, 2022 by Stephen Ogier 38 Comments

The PCB business card has long been a way for the aspiring electronics engineer to set themself apart from their peers. Handing out a card that is also a two player game is a great way to secure a couple minutes of a recruiter’s time, so [Ryan Chan] designed a business card that, in addition to his contact information, also has a complete Tic-Tac-Toe game built in.

[Ryan] decided that an OLED display was too expensive for something to hand out and an LED matrix too thick, so he decided to keep it simple and use an array of 18 LEDs—9 in each of two colors laid out in a familiar 3×3 grid. An ATmega328p running the Arduino bootloader serves as the brains of the operation. To achieve a truly minimal design [Ryan] uses a single SMD pushbutton for control: a short press moves your selection, a longer press finalizes your move, and a several-second press switches the game to a single-player mode, complete with AI.

If you’d like to design a Tic-Tac-Toe business card for yourself, [Ryan] was kind enough to upload the schematics and code for his card. If you’re still pondering what kind of PCB business card best represents you, it’s worth checking out cards with an updatable ePaper display or a tiny Tetris game.

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Future Brings CPU Modules, And The Future Is Now

September 14, 2022 by Arya Voronova 36 Comments

Modularity is a fun topic for us. There’s something satisfying about seeing a complex system split into parts and these parts made replaceable. We often want some parts of our devices swapped, after all – for repair or upgrade purposes, and often, it’s just fun to scour eBay for laptop parts, equipping your Thinkpad with the combination of parts that fits you best. Having always been fascinated by modularity, I believe that hackers deserve to know what’s been happening on the CPU module front over the past decade.

A Youtube thumbnail showing a Thinpad in the background with "Not Garbage" written over its keyboard, and one more keyboard overlaid onto the picture with "garbage" written on that one. — This “swap your Thinkpad keyboard” video thumbnail captures a modularity-enabled sentiment many can relate to.

We’ve gotten used to swapping components in desktop PCs, given their unparalleled modularity, and it’s big news when someone tries to split a yet-monolithic concept like a phone or a laptop into modules. Sometimes, the CPU itself is put into a module. From the grandiose idea of Project Ara, to Intel’s Compute Card, to Framework laptop’s standardized motherboards, companies have been trying to capitalize on what CPU module standardization can bring them.

There’s some hobbyist-driven and hobbyist-friendly modular standards, too – the kind you can already use to wrangle a powerful layout-demanding CPU and RAM combo and place it on your simple self-designed board. I’d like to tell you about a few notable modular CPU concepts – their ideas, complexities, constraints and stories. As you work on that one ambitious project of yours – you know, the one, – it’s likely you will benefit a lot from such a standard. Or, perhaps, you’ll find it necessary to design the next standard for others to use – after all, we all know there’s never too few standards! Continue reading “Future Brings CPU Modules, And The Future Is Now” →

What Every PCB Designer Needs To Know About Track Impedance With Eric Bogatin

September 12, 2022 by Dave Rowntree 7 Comments

PCB design starts off being a relatively easy affair — you create a rectangular outline, assign some component footprints, run some traces, and dump out some Gerber files to send to the fab. Then as you get more experienced and begin trying harder circuits, dipping into switching power supplies, high speed digital and low noise analog, things get progressively more difficult; and we haven’t even talked about RF or microwave design yet, where things can get just plain weird from the uninitiated viewpoint. [Robert Feranec] is no stranger to such matters, and he’s teamed up with one of leading experts (and one of this scribe’s personal electronics heroes) in signal integrity matters, [Prof. Eric Bogatin] for a deep dive into the how and why of controlled impedance design.

RG58 cable construction. These usually are found in 50 Ω and less commonly these days 75Ω variants

One interesting part of the discussion is why is 50 Ω so prevalent? The answer is firstly historical. Back in the 1930s, coaxial cables needed for radio applications, were designed to minimize transmission loss, using reasonable dimensions and polyethylene insulation, the impedance came out at 50 Ω. Secondarily, when designing PCB traces for a reasonable cost fab, there is a trade-off between power consumption and noise immunity.

As a rule of thumb, lowering the impedance increases noise immunity at the cost of more power consumption, and higher impedance goes the other way. You need to balance this with the resulting trace widths, separation and overall routing density you can tolerate.

Another fun story was when Intel were designing a high speed bus for graphical interfaces, and created a simulation of a typical bus structure and parameterized the physical constants, such as the trace line widths, dielectric thickness, via sizes and so on, that were viable with low-cost PCB fab houses. Then, using a Monte Carlo simulation to run 400,000 simulations, they located the sweet spot. Since the via design compatible with the cheap fab design rules resulted often in a via characteristic impedance that came out quite low, it was recommended to reduce the trace impedance from 100 Ω to 85 Ω differential, rather than try tweak the via geometry to bring it up to match the trace. Fun stuff!

We admit, the video is from the start of the year and very long, but for such important basic concepts in high speed digital design, we think it’s well worth your time. We certainly picked up a couple of useful titbits!

Now we’ve got the PCB construction nailed, why circle back and go check those cables?

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MH-Z19-like NDIR CO2 Sensor HC8 Found And Explored

August 31, 2022 by Maya Posch 7 Comments

While on the search for an alternative to directly buying the fairly expensive MH-Z19 CO2 sensor, [spezifisch] came across a ‘BreeRainz’ branded gadget (also found under other brands) that claimed to use an NDIR (Non-Dispersive Infrared) sensor for measuring CO2 levels, while costing only €25. This type of sensor allows for CO2 levels to be measured directly, rather than inferred, making them significantly more precise.

The BreeRainz DM1308A device cracked open.

After cracking the gadget open (literally, due to the hidden screws), the CO2 sensor is clearly visible. While superficially identical to an MH-Z19, the NDIR sensor is actually called ‘HC8’, is produced by 广州海谷电子科技有限公司 (Guangzhou Haigu Electronic Technology Co., Ltd.). While being pin-compatible with the MH-Z19, its UART protocol is not the same. Fortunately there is a datasheet to help with implementing it, which is what [spezifisch] did.

This raises the question of whether harvesting NDIR CO2 sensors like this is worth it to save a few Euros. A quick look on German Amazon shows that the device in question currently costs €35, while a genuine MH-Z19 can be bought for €25 or less. There are also many MH-Z19 models (B, C and D), which cover an even wider price range. All of which points to finding an NDIR sensor-containing device can be interesting when it’s on sale, but if all you care about is the sensor itself, it’s probably best to just buy them directly.