PiNet — One Small Project Grows Unexpectedly

A few years ago, [Gregory Sanders] aka [Dr Gerg] had one simple wish in mind when he started what is now the PiNet project — to know whether his garage door was open or closed. Instead of searching out off-the-shelf solutions, he looked at the project as a learning opportunity. After picking up Python, he built a system from a Raspberry Pi, a 12V gel cell battery, and a power supply / charger circuit. Thus project Overhead Door (ohd) was complete (see the ohd GitHub repository) and [Dr Gerg] was done.

Or so he thought. After getting a swimming pool installed, he got the itch again, and started a new project called Pool Controls, because:

The controls for your average backyard in-ground pool are pathetic. I felt like I could do better with a Raspberry Pi, a relay board and some Python. And so I did, and frankly, it’s awesome.

Then he built his own weather station to replaced a commercial one which had died twice in as many years, followed by his own web-based UI framework. Next was the integration of an outdoor security camera system. And finally, although we don’t believe it’s really final, he ripped out the cloud-based controls from his shop air conditioner and added his own Raspberry Pi-based solution. All of these projects are available on his GitHub page.

[Dr Gerg]’s goal in posting all this work is not necessarily so people can duplicate it, although that is okay as well. Instead, he hopes that people will realize that they can build these types of projects on their own, perhaps leaning some things and picking up new skills along the way — have fun doing it. We like the way you think, [Dr Gerg]. Do you know of any small projects which grew and grew and took on a life of their own?

Some Of The Many Ways To Build AM Transmitters And Receivers

AM radios are relatively simple devices, and building one is a good way to start exploring the world of radio communications. [GreatScott] does exactly this in the video after the break, building both a transmitter and receiver.

At the most basic level, AM radio works by generating a carrier wave with an oscillator, and then modulating the amplitude with an audio signal. Around these parts, the venerable 555 timer is always brought up whenever things get to oscillating; so you’ll no doubt be happy to see [GreatScott] decided to give it a shot for his first experiments, testing two popular 555 transmitter circuits. One uses the control voltage pin to input the audio signal, while the other uses the reset pin. The CV-pin version worked slightly better, but it was still just barely possible to distinguish a voice over a standard commercial AM/FM receiver.

The next attempt was with a XR2206 function generator kit, which worked quite well when combined with a simple microphone amplifier circuit. But this time the receiving side was swapped out, as [GreatScott] built a basic circuit around a TA7642 AM amplifier/demodulator IC, with only six passive components and a hand-wound coil.

There is no shortage of ways to build AM radios, and we’ve covered quite a few over the years. Off course a 555 timer can also be used in a receiver, and building transmitters using only discrete components is quite simple, as demonstrated by the 10-minute transmitter and single transistor transmitter.

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A Custom Clock With LED Filament Hands

LEDs have become so ubiquitous in our projects that just hearing that term probably conjures images of tiny illuminated domes in an array of single-spectrum colors. It’s easy to forget that these efficient sources of light come in a variety of form factors, including the retro-tacular filaments that [bitborked] used to make his beautiful analog LED wall clock.

Aside from its aesthetics, this timepiece features some great design. A custom PCB acts as a hub for all the LED filament spokes. The onboard brains come in the form of an ESP32, which means it can keep extremely accurate time via NTP. WS2811 LED controllers, which we’re so accustomed to seeing alongside RGB LEDs that they almost feel strange to see here, provide the 12 volts required for each filament and make individual addressing a breeze.

[bitborked] takes advantage of that addressability to display other animations in addition to the standard clock face. They also plan to implement MQTT for eventual alerts from other home automation devices. When it comes to just telling time, you can discern the individual “hands” by differences in their brightness, which sadly does not show up as well in video as it does in real life.

We would certainly be happy to have this clock on our walls, and we hope to eventually see more of its PCB designs. In the meantime, though, we can drool over a more digital take on the LED filament clock. Although, filaments are certainly not required to make a beautiful LED timekeeper.

Casting A Simple 3D Print In Aluminium

3D printing with plastics and resins is great for quickly prototyping parts with all manner of geometries, but strength and durability of the parts produced is often limited. One way around this is to use your 3D printed parts as patterns for casting in something tougher like aluminium. That’s precisely what [Brian Oltrogge] did to produce an attractive wall hook from a 3D printed design.

The process starts with the design and printing of a wall hook, with [Brian] taking care to include the proper draft angles to allow the pattern to be properly removed from the mold. The print is carefully sanded down and post-processed to be highly smooth, so that it doesn’t spoil the mold when its removed for the casting process. From there, a sand casting mold is built around the pattern using sodium silicate in a 3-4% mix by weight with fine masonry sand. Once ready, the pattern is removed, and the mold is assembled, ready for the pour.

[Brian] completes the process with a simple gravity casting method using molten aluminium. The part is then removed from the mold, and filed down to improve the surface finish from the sand casting process. It’s then polished up to a nice shine and hung on the wall.

[Brian] does a great job of explaining the basics of what it takes to get gravity casting right; draft angles in particular are something often ignored by beginners, yet are crucial to getting good results. You needn’t just settle for casting inanimate objects though; we’ve featured DIY casting processes for gears before, too. Video after the break.

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Will We Soon Be Running Linux On SiFive Cores Made By Intel?

There’s an understandably high level of interest in RISC-V processors among our community, but while we’ve devoured the various microcontroller offerings containing the open-source core it’s fair to say we’re still waiting on the promise of more capable hardware for anything like an affordable price. This could however change, as the last week or so has seen a flurry of interest surrounding SiFive, the fabless semiconductor company that has pioneered RISC-V technology. Amid speculation of a $2 billion buyout offer from the chip giant Intel it has been revealed that the company best known for the x86 line of processors has licensed the SiFive portfolio for its 7nm process. This includes their latest and fastest P550 64-bit core, bringing forward the prospect of readily available high-power RISC-V computing. Your GNU/Linux box could soon have a processor implementing an open-source ISA, without compromising too much on speed and, we hope, price.

All this sounds pretty rosy, but there is of course a downer for open-source hardware enthusiasts. These chips may rely on some open-source technologies, but sadly they will not themselves be open-source chips as there will be plenty of proprietary IP contained within them. We can thus only hope that Intel see fit to provide the same level of Linux support for them as they do for their x86 ranges, and we’re not left in the same situation with respect to ongoing support as we are with so many other chips. Meanwhile it’s worth remembering that SiFive are not the only player in the world of RISC-V cores, so it’s likely that competitors to the P550 and its stablemates will not be far behind.

If you’d like a more in-depth explanation of the true open-source nature of a RISC-V chip, we’ve featured something on that theme before.

Header image: Gareth Halfacree, CC BY-SA 2.0.

Know Audio: A Loudspeaker Primer

As we’ve started out on our journey through the world of Hi-Fi audio from a strictly practical and engineering viewpoint without being misled by any audiophile woo, we’ve already taken a look at the most important component in any audio system: the listener’s ear. It’s time to move down the chain to the next link; the loudspeaker.

Sound is pressure waves in the air, and the purpose of a loudspeaker is to move the air to create those waves. There are a variety of “exotic” loudspeaker technologies including piezoelectric and electrostatic designs, here we’ll be considering the garden variety moving-coil speaker. It’s most usually used for the large bass or smaller mid-range drivers in a typical speaker system. Continue reading “Know Audio: A Loudspeaker Primer”

Hackaday Podcast 124: Hard Drivin’ With Graphene, Fooled By Lasers, Etching With Poison Acid, And All The Linux Commands

Hackaday editors Elliot Williams and Mike Szczys marvel at the dangerous projects on display this week, including glass etching with hydrofluoric acid and pumping 200,000 A into a 5,000 A fuse. A new board that turns the Raspberry Pi into an SDR shows off the power of the secondary memory interface (SMI) present in those Broadcom chips. We also discuss the potential for graphene in hard drives, and finish up with a teardown of a very early electronic metronome.

You know you want to read the show notes!

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (55 MB or so.)

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