Author: Bryan Cockfield

1852 Articles

Pi Compute Module Is Love-child Of Raspberry And Arduino

December 14, 2020 by 27 Comments

The Raspberry Pi compute module is a powerful piece of hardware, especially for the price. With it, you get more IO than a normal Pi, plus the ability to design hardware around it that’s specifically tailored to your needs rather than simply to general-purpose consumers. However, this comes at the cost of needing a way to interface with it since the compute module doesn’t have the normal IO pins or ports, but [Timon] has come up with a handy development board for this module called the Piunora which solves a lot of these prototyping issues.

The development board expands the compute module to the familiar Arduino-like form factor, complete with IO headers, USB ports, and HDMI output. It doesn’t stop there, though. It has an M.2 connector, some built-in LEDs, a camera connector, and a few other features. It also opens up some other possibilities that would be difficult or impossible with a standard Pi 4, such as the ability to run the Pi as a USB gadget rather than as a host device which simplifies certain types of development, which is [Timon]’s intended function.

As a development board, this project has a lot of potential for the niche uses of the compute module when compared to the standard Raspberry Pi. For embedded applications it’s much easier to deploy, with the increased development costs as a tradeoff. If you’re still unsure what to do with the compute module 4, we have some reading for you. And Timon’s previous project is a great springboard.

PET 2001 Emulator On $2 Of Hardware

December 9, 2020 by 20 Comments

Since the late 60s, Moore’s law has predicted with precision that the number of semiconductors that will fit on a chip about doubles every two years. While this means more and more powerful computers, every year, it also means that old computers can be built on smaller and cheaper hardware. This project from [Bjoern] shows just how small, too, as he squeezes a PET 2001 onto the STM32 Blue Pill.

While the PET 2001 was an interesting computer built by Commodore this project wasn’t meant to be a faithful recreation, but rather to test the video output of the Blue Pill, with the PET emulation a secondary goal. It outputs a composite video signal which takes up a good bit of processing power, but the PET emulation still works, although it is slightly slow and isn’t optimized perfectly. [Bjoern] also wired up a working keyboard matrix as well although missed a few wire placements and made up for it in the software.

With his own home-brew software running on the $2 board, he has something interesting to display over his composite video output. While we can’t say we’d emulate an entire PC just to get experience with composite video, we’re happy to see someone did. If you’d like to see a more faithful recreation of this quirky piece of computing history, we’ve got that covered as well.

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Speaker Snitch Tattles On Privacy Leaks

December 9, 2020 by 33 Comments

A wise senator once noted that democracy dies with thunderous applause. Similarly, it’s also how privacy dies, as we invite more and more smart devices willingly into our homes that are built by companies that don’t tend to have our best interests in mind. If you’re not willing to toss all of these admittedly useful devices out of the house but still want to keep an eye on what they’re doing, though, [Nick Bild] has a handy project that lets you keep an eye on them when they try to access the network.

The device is built on a Raspberry Pi that acts as a middle man for these devices on his home network. Any traffic they attempt to send gets sent through the Pi which sniffs the traffic via a Python script and is able to detect when they are accessing their cloud services. From there, the Pi sends an alert to an IoT Arduino connected to an LED which illuminates during the time in which the smart devices are active.

The build is an interesting one because many smart devices are known to listen in to day-to-day conversation even without speaking the code phrase (i.e. “Hey Google” etc.) and this is a great way to have some peace-of-mind that a device is inactive at any particular moment. However, it’s not a foolproof way of guaranteeing privacy, as plenty of devices might be accessing other services, and still other devices have  even been known to ship with hidden hardware.

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Killing Mosquitoes With Cardi B

December 5, 2020 by 31 Comments

Keeping a bird bath or a pond in your yard is a great way to add ambiance and style, but both of these things can be a haven for mosquitoes. Popular methods of getting rid of them are often with harsh pesticides, but [Shane] has brought us a more environmentally-friendly way of taking care of these disease-carrying insects by looping a Cardi B playlist underwater, killing the mosquito larvae.

While the build does include some other favorites such as “Baby Shark” and would probably work with any song (or audio of sufficient volume) the build is still pretty interesting. It’s based on a 555 timer circuit which powered an ultrasonic sound gun, but was repurposed for this build. The ultrasonic modules were replaced with piezo modules which were waterproofed with silicone. The sound produced vibrates at a frequency which resonates with the mosquito larvae and is fatal to them. [Shane] put the build into a small boat which can be floated in any pond, bird bath, horse trough, or water feature.

The major caveat to this build is that it may be damaging to other beneficial animals such as fish or frogs, so he suggests limiting its use to uninhabited stagnant water. Either way, though, it’s a pretty unique way of taking care of a mosquito problem not unlike another build which takes care of these insects in water a slightly different way.

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FM Radio From Scratch Using An Arduino

December 4, 2020 by 50 Comments

Building radio receivers from scratch is still a popular project since it can be done largely with off-the-shelf discrete components and a wire long enough for the bands that the radio will receive. That’s good enough for AM radio, anyway, but you’ll need to try this DIY FM receiver if you want to listen to something more culturally relevant.

Receiving frequency-modulated radio waves is typically more difficult than their amplitude-modulated cousins because the circuitry necessary to demodulate an FM signal needs a frequency-to-voltage conversion that isn’t necessary with AM. For this build, [hesam.moshiri] uses a TEA5767 FM chip because of its ability to communicate over I2C. He also integrated a 3W amplifier into this build, and everything is controlled by an Arduino including a small LCD screen which displays the current tuned frequency. With the addition of a small 5V power supply, it’s a tidy and compact build as well.

While the FM receiver in this project wasn’t built from scratch like some AM receivers we’ve seen, it’s still an interesting build because of the small size, I2C capability, and also because all of the circuit schematics are available for all of the components in the build. For those reasons, it could be a great gateway project into more complex FM builds.

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Hardware Keymapper Routes Through Raspberry Pi

December 3, 2020 by 19 Comments

There are a lot of keyboards to choose from, and a quick trip through some of the forums will quickly show you how fanatical some people can be about very specific styles or switches. [Crdotson] doesn’t seem to be too far down the rabbit hole in that regard, but he does have a keyboard that he really likes despite one small quirk: it’s built for Mac, and some of the modifier keys aren’t laid out correctly for Windows. Since Windows has limited (and poor) options for software keymapping, he took an alternative route and built a keymapper in hardware instead.

The build uses a Raspberry Pi as a go-between from the keyboard to his computer. The Pi watches the USB bus using usbmon, which allows inspection of the packets and can see which keys have been pressed. It then passes those keypresses through to the computer. His only modification to the keyboard mapping is to swap the Alt and Super (Windows) keys for his keyboard of choice, although using this software would allow any other changes to be made as well. Latency is only on the order of a few microseconds, which is not noticeable for normal use cases.

While we have seen plenty of other builds around that can map keyboards in plenty of custom ways, if you don’t have the required hardware for a bespoke solution it’s much more likely that there’s a Raspberry Pi laying around that can do the job instead. There are a few issues with the build that [crdotson] is planning to tackle, though, such as unplugging the device while a key is being pressed, which perpetually sends that keystroke to the computer without stopping. But for now it’s a workable solution for his problem.

Recovering Metal From Waste

November 30, 2020 by 10 Comments

Refining precious metals is not as simple as polishing rocks that have been dug out of the ground. Often, complex chemical processes are needed to process the materials properly or in high quantities, but these processes leave behind considerable waste. Often, there are valuable metals left over in these wastes, and [NerdRage] has gathered his chemistry equipment to demonstrate how it’s possible to recover these metals.

The process involved looks to recover copper and nitric acid from copper nitrate, a common waste byproduct of processing metal. While a process called thermal decomposition exists to accomplish this, it’s not particularly efficient, so this alternative looks to improve the yields you could otherwise expect. The first step is to react the copper nitrate with sulfuric acid, which results in nitric acid and copper sulfate. From there, the copper sulfate is placed in an electrolysis cell using a platinum cathode and copper anodes to pass current through it. After the process is complete, all of the copper will have deposited itself on the copper electrodes.

The other interesting thing about this process, besides the amount of copper that is recoverable, is that the sulfuric acid and the nitric acid are recoverable, and able to be used again in other processes. The process is much more efficient than thermal decomposition and also doesn’t involve any toxic gasses either. Of course, if collecting valuable metals from waste is up your alley, you can also take a look at recovering some gold as well.

Thanks to [Keith] for the tip!

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