3D Printed Flip Dots

May 29, 2021 by 9 Comments

Displays have come a long way in the last few decades, but none can deliver the mesmerizing visual and audio experience of a large flip dot display. Both old panels and new panels can be expensive and difficult to source, so [Larry Builds] made his own flip dots with the help of 3D printing.

Flip dots are driven by a pair of electromagnetic posts that attract or repel a magnet embedded in the dot, and [Larry Builds] version is no different. For the electromagnets, he used M3 threaded rod with enamel wire wound around them using a drill. At first, he used a large magnet in the center of the 3D printed dot, but the magnetic field was large and strong enough to flip the surrounding dots in an array. He then changed the design to a small 4 mm diameter magnet in the edge that aligns directly with the electromagnets. This design looks very similar to those used by Breakfast for their massive installations. By modifying electromagnets and adding spacers around the magnets, he was able to reduce the operating current from 2 A to below 500 mA. [Larry Builds] also breadboarded a basic driver circuit consisting of H-bridges multiplexed to rows and columns with diodes.

We will be keeping a close eye on this project, and we look forward to seeing it evolve further. It’s definitely on our “things to build” list. We’ve embedded multiple videos after the break showing the progress thus far.

We’ve covered several interesting flip dot projects, including a water level indicator that doesn’t use any electronics and another that is crocheted. Continue reading “3D Printed Flip Dots” →

Build A New ZX81

May 28, 2021 by 17 Comments

[Retro Shack’s] ZX81 died, and while he tried to figure out the fix, he decided to build a new one. Of course, building a circa-1980-something computer from new parts is a bit daunting. Unless you start with an existing design that has it all ready to put together.

The PCB looks great and we like that the silkscreen shows acknowledgments of projects that helped the designer, [Alejandro Sebastian]. The case is, of course, 3D printed. At first, the power LED didn’t work, but voltages looked correct and the board powered up.

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Web Assembly, Music Synthesis, And The Beauty Of Math

May 28, 2021 by 9 Comments

The electronics hobby has changed a lot since the advent of the microprocessor. Before that — and with the lack of large-scale integrated circuits — projects in magazines tended to be either super simple or ultra complex. However, one popular type of project dealt with music synthesis. Fairly simple circuits could combine to make a complex synthesizer so it was sort of the best of both worlds. Nowadays, you are more likely to tackle a music synthesizer in software like [Tim] did when he created Abelton in Web Assembly and C++. Along the way, he learned a lot about the relationship between math and music.

[Tim] covers what he learned about the Nyquist theorem and how to keep synthesis data flowing in real time with buffers. However, there are some problems trying to do all this in a cross-browser context. The AudioWorklet class appears to have widespread support, though, and [Tim] managed to get that working.

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JTAG Hat Turns Raspberry Pi Into A Networked Debugger

May 28, 2021 by 7 Comments

Over the last year or so we’ve noticed a definite uptick in the number of folks using OpenOCD on the Raspberry Pi. It’s a cheap and convenient solution for poking around with various microcontrollers and embedded devices, but not always the most elegant. Looking to improve on the situation somewhat, [Matthew Mets] has been working on a purpose-built JTAG Hat to clean things up a bit.

Onboard level shifters allow you connect to JTAG and SWD interfaces from 1.8 to 5 V, and if you power the target device from the Pi itself, there’s even support for measuring the voltage and current. To connect up to your target, the open hardware board features a “legacy” pin header perfect for jumper wires, as well as a dedicated 10-pin Cortex Debug Connector. Whether you spin up your own or buy one assembled, it certainly looks like a tool worth having around if you often find yourself working with the appropriate chips.

In addition to the design files for the hardware, [Matthew] has also provided some nice documentation on how to get the software side of things up and running. Starting with a blank SD card, it walks you through the initial setup of the Raspberry Pi all the way through the installation and configuration of a patched version of OpenOCD designed to support the JTAG Hat.

If you spend more time working with 8-bit AVR chips, don’t worry. Last year we covered a similar project to turn everyone’s favorite Linux SBC into an all-in-one microcontroller development powerhouse.

3D Printing A Centrifugal Water Pump

May 28, 2021 by 43 Comments

Once upon a time, 3D printing was about churning out tiny Yodas and Pikachus, but these days, useful things are regularly 3D printed too. A great example is this centrifugal water pump that can really deliver the juice, courtesy of  [Connor].

The pump’s housings and impeller are all 3D printed in PLA, as well as the inlet which is designed for a 2L soda bottle to screw into. Gaskets are printed in pliable TPU to help seal the housings. There are a few ball bearings inside to allow the impeller to spin nicely, too, with hex head fasteners used to hold everything together and a long bolt used as the main impeller shaft. Notably, no shaft seal is included, so the pump does leak a bit, but it’s not a major concern assuming you’re just pumping water and don’t mind spilling a bit of excess. Turned with a drill at 1800 rpm, the pump is able to achieve a flow rate of 13 litres per minute, or a maximum head of 1.2 meters. The design is on Onshape, for the curious.

It’s a great example of how 3D printing can allow the creation of machines with complex geometry without the need for advanced machining skills. Instead, all the hard work is done on the CAD side of things. We’ve seen 3D printed pumps put to real work before, too, like this fertilizer dispenser. Video after the break.

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Put APIs To Work Wth This ArduinoJson Walkthrough

May 28, 2021 by 6 Comments

One of the things this community is famous for is the degree to which people will pitch in to fill an obvious need. Look at the vast array of libraries available for Arduino as an example of how people are willing to devote their time to making difficult tasks easier, often for little more than a virtual pat on the back.

One level up from the library writers are those who go through the trouble of explaining how all these libraries work in real-world applications. [Brian Lough] recently rose to that challenge with a thorough explanation of the use of the ArduinoJSON library, a very useful but often confusing library that makes IoT projects easier.

The need for an ArduinoJSON explainer no knock on its author, [Benoît Blanchon], who has done excellent work documenting the library; it’s more of a realization that the nature of JSON itself means a library that works with it is going to be complex. [Brian]’s contribution here is sharing his insights into getting ArduinoJSON up and running in a real-world ESP32 example, and dealing with the potential pitfalls of parsing a human-readable text file that can be used to represent almost any data object using the limited resources of a microcontroller. Along with the basics, we found the warning about how pointers refer back to the dynamic JSON document object particularly helpful; the bit about using filters to winnow down a large data set was useful too.

Thanks to [Brian] for taking the time to put this valuable information out there. Here’s hoping this encourages others to share the wealth of hard-earned knowledge in a similarly clear and concise manner.

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The Many Levels Of Autonomous Motoring

May 28, 2021 by 40 Comments

For years now we have been told that self-driving cars will be the Next Big Thing, and we’ve seen some companies — yes, Tesla but others too — touting current and planned features with names like “Autopilot” and “self-driving”. Cutting through the marketing hype to unpacking what that really means is difficult. But there is a standard for describing these capabilities, assigning them as levels from zero to five.

Now we’re greeted with the news that Honda have put a small number of vehicles in the showrooms in Japan that are claimed to be the first commercially available level 3 autonomous cars. That claim is debatable as for example Audi briefly had level 3 capabilities on one of their luxury sedans despite having few places to sell it in which it could be legally used. But the Honda Legend SENSING Elite can justifiably claim to be the only car on the market to the general public with the feature at the moment. It has a battery of sensors to keep track of its driver, its position, and the road conditions surrounding it. The car boasts a “Traffic Jam Pilot” mode, which “enables the automated driving system to drive the vehicle under certain conditions, instead of the driver, such as when the vehicle is in congested traffic on an expressway“.

Sounds impressive, but just what is a level 3 autonomous car, and what are all the other levels?

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