2023 Halloween Hackfest: Candy Basket Sees You Coming

October 14, 2023 by Kristina Panos 5 Comments

On Halloween, some people can’t or don’t want to open the door for various reasons. Maybe they have a cat that likes to escape every chance it gets, or maybe their favorite TV show is on during prime trick-or-treating time. Whatever the case, we think it’s perfectly acceptable to leave a bowl of candy outside the door, especially if there are electronics involved.

In this case, the bowl detects trick-or-treaters and candy eaters using an LD2410 60 GHz radar sensor and an RP2040. A light pipe shows orange when a person is detected, and switches over to green as they come closer, as if to say you may have candy now.

Nothing happens after that, but now that we think about it, it would be cool to add an MP3 decoder and a speaker to play a little witch cackle or something once they’ve had a chance to stick their hand in the bucket.

[Mike Kushnerik] actually designed the PCB a few months ago for non-Halloween purposes: some home automation projects. But then they were trying to think of something for Halloween, and this delightful light-up bucket came to mind. In addition to the RP2040 chip, there’s a 128 MB flash chip, a WS2812 LED, and a header for communicating with the radar sensor over UART. Be sure to check out the brief demo video after the break.

If you’d like to stand outside and give out candy, at least send it down a light-up slide or something.

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Lessons Learned: Plastic Injection Molding For Products

October 14, 2023 by Donald Papp 23 Comments

Injection molding is one of the technologies that makes the world go round. But what does it actually look like to go through the whole process to get a part made? [Achim Haug] wrote up a blog post that does a fantastic job of explaining what to expect when getting plastic enclosures injection molded in China.

These air quality monitors required a two-part enclosure.

Injection molding a part requires making a custom mold, which is then used by an injection molding machine in a shop to crank out parts. These are two separate jobs, but in China the typical business model is for a supplier to quote a price for both the mold as well as the part production. [Achim] describes not only what navigating that whole process was like, but also goes into detail on what important lessons were learned and shares important tips.

One of the biggest takeaways is to design the part with injection molding in mind right from the start. That means things like avoiding undercuts and changes in part thickness, as well as thinking about where the inevitable mold line will end up.

[Achim] found that hiring a been-there-done-that mold expert as a consultant to review things was a huge help, and well worth the money. As with any serious engineering undertaking, apparently small features or changes can have an outsized impact on costs, and an expert can recognize and navigate those.

In the end, [Achim] says that getting their air quality monitor enclosures injection molded was a great experience and they are very happy with the results, so long as one is willing to put the work in up front. Once the mold has been made, downstream changes can be very costly to make.

[Achim]’s beginning-to-end overview is bound to be useful to anyone looking to actually navigate the process, and we have a few other resources to point you to if you’re curious to learn more. There are basic design concerns to keep in mind when designing parts to make moving to injection molding easier. Some injection molding techniques have even proven useful for 3D printing, such as using crush ribs to accommodate inserted hardware like bearings. Finally, shadow lines can help give an enclosure a consistent look, while helping to conceal mold lines.

Close To The Metal

October 14, 2023 by Elliot Williams 81 Comments

Firmware is caught between hardware and software. What do I mean? Microcontroller designers compete on how many interesting and useful hardware peripherals they can add to the chips, and they are all different on purpose. Meanwhile, software designers want to abstract away from the intricacies and idiosyncrasies of the hardware peripherals, because code wants to be generic and portable. Software and hardware designers are Montagues and Capulets, and we’re caught in the crossfire.

I’m in the middle of a design that takes advantage of perhaps one of the most idiosyncratic microcontroller peripherals out there – the RP2040’s PIOs. Combining these with the chip’s direct memory access (DMA) controllers allows some fairly high-bandwidth processing, without bogging down the CPUs. But because I want this code to be usable and extensible by a wide audience, I’m also trying to write it in MicroPython. And configuring DMA controllers is just too idiosyncratic for MicroPython.

But there’s an escape hatch. In my case, it’s courtesy of the machine.mem32 function, which lets you read and write directly into the chip’s memory, including all of the memory-mapped configuration registers. Sure, it’s absurdly low-level, but it means that anything you read about in the chip’s datasheet, you can do right away, and from within the relative comfort of a Micropython program. Other languages have their PEEK and POKE equivalents as well, or allow inline assembler, or otherwise furnish you the tools to get closer to the metal without having to write all the rest of your code low level.

I’m honestly usually a straight-C or even Forth programmer, but this experience of using a higher-level language and simultaneously being able to dive down to the lowest levels of bit-twiddling at the same time has been a revelation. If you’re just using Micropython, open up your chip’s datasheet and see what it can offer you. Or if you’re programming at the configure-this-register level, check out the extra benefits you can get from a higher-level language. You can have your cake and eat it too!

Making A Concrete Sign

October 14, 2023 by Jenny List 18 Comments

While paging through the feed a few days ago our attention was caught by something a little away from the ordinary in Hackaday terms, a DIY video about creating cast concrete signage from [Proper DIY] which we’ve placed below the break. A deceptively easy-looking mould-making process has a few tricks that will make the difference between a hard-wearing sign that lasts for years, and a lump of concrete.

So, to make a cast concrete sign, you throw together a mould with some letters, and chuck in some concrete? Not so fast, because the key appears to be preparation, and ensuring that there are no 90-degree corners on the mould parts. The letters are carefully shaped and sealed with varnish before being attached to the mould with silicone adhesive, and all the corners are beveled. Finally a light oil is used as a release agent, and hefty vibration takes care of any air bubbles.

The result is a set of signs, but we can see these techniques finding uses outside signage. For example, how about casting using a 3D printed mould?

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This 3D Printable Soldering Air Filter Really Sucks

October 14, 2023 by Kristina Panos 24 Comments

If you solder (and we know you do), you absolutely need ventilation, even for that lead-free stuff. Fortunately, [tinyboatproductions] has gotten into air quality lately and is here to help you with their snappy 3D printed air-filtering design.

At the heart of this build is a 120 mm notoriously-quiet Noctua fan coupled with a carbon filter. It does what you’d think — position the fan the right way and it sucks the air through the filter, which catches all those nasty particles.

The only problem is that the Noctua uses PWM, so there’s no governing it with a just potentiometer. To get around this, [tinyboatproductions] introduced an Arduino Nano and a buck converter, both of which were admittedly a bit overkill. Now the speed can be controlled with a pot.

Once control of the fan was sorted, [tinyboatproductions] decide to add an OLED display to show the fan speed and power condition, which is a nice touch. Be sure to check out the build video after the break.

If this doesn’t have quite enough features for you, here’s one that’s battery powered.

Continue reading “This 3D Printable Soldering Air Filter Really Sucks” →

Because You Can: Linux On An Arduino Uno

October 13, 2023 by Jenny List 26 Comments

There are a few “Will it run” tropes when it comes to microcontrollers, one for example is “Will it run Doom?“, while another is “Will it run Linux?”. In one of the lowest spec examples of the last one, [gvl610] has got an up-to-date Linux kernel to boot on a vanilla Arduino Uno. And your eyes didn’t deceive you, that’s a full-fat kernel rather than the cut-down μClinux for microcontrollers.

Those of you who’ve been around a while will probably have guessed how this was done, as the ATmega328 in the Uno has no MMU and is in to way powerful enough for the job. It’s running an emulator, in this case just enough RISC-V to be capable, and as you’d imagine it’s extremely slow. You’ll be waiting many hours for a shell with this machine.

The code is written in pure AVR C, and full instructions for compilation are provided. Storage comes from an SD card, as the ATmega’s meagre 32k is nowhere near enough. If you’re having a bit of deja vu here we wouldn’t blame you, but this one is reputed to be worse than the famous 2012 “Worst PC Ever“, which emulated ARM instead of RISC-V.

Thanks [Electronics Boy] for the tip!

Restoration Of A Thinkpad 701C

October 13, 2023 by Richard Baguley 9 Comments

This is like ASMR for Hackers: restoration specialist [Polymatt] has put together a video of his work restoring a 1995 IBM Thinkpad 701c, the famous butterfly keyboard laptop. It’s an incredible bit of restoration, with a complete teardown and rebuild, even including remaking the decals and rubber feet.

[Polymatt] runs Project Butterfly, an excellent site for those who love these iconic laptops, offering advice and spare parts for restoring them. In this video, he does a complete teardown, taking the restored laptop completely apart, cleaning it out, and replacing parts that are beyond salvaging, like the battery, and replacing them. Finally, he puts the whole thing back together again and watches it boot up. It’s a great video that we’ve put below the break and is well worth watching if you wonder about how much work this sort of thing involves: the entire process took him over two years.

We’ve covered some of his work in the past, including the surprisingly complicated business of analyzing and replacing the Ni-Cad battery that the original laptop used. Continue reading “Restoration Of A Thinkpad 701C” →