DIY 8-Bit Computer Knows All The Tricks

December 31, 2020 by Bryan Cockfield 12 Comments

Some projects are a rite of passage within their respected fields. For computer science, building one’s own computer from scratch is certainly among those projects. Of course, we’re not talking about buying components online and snapping together a modern x86 machine. We mean building something closer to a fully-programmable 8-bit computer from the ground up, like this one from [Federico] based on 74LS logic chips.

The computer was designed and built from scratch which is impressive enough, but [Federico] completed this project in about a month as well. It can be programmed manually through DIP switches or via a USB connection to another computer, and also includes an adjustable clock which can perform steps anywhere from 1 Hz to 32 kHz. Complete with a 1024 byte memory, a capable ALU, four seven-segment LEDs and (in the second version of the computer) a 2×16 LCD disply, this 8-bit computer has it all.

Not only is this a capable machine designed by someone who clearly knows his way around a logic chip, but [Federico] has also made the code and schematics available on his GitHub page. It’s worth a read even without building your own, but if you want to go that route without printing an enormous PCB you can always follow the breadboard route.

Thanks to [killergeek] for the tip!

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Slick DIY Compound Bow Uses Coiled Springs, Toothbrush Heads

December 12, 2020 by Donald Papp 14 Comments

Compound bows (unlike recurve bows, their more mechanically-simple relatives) use a levering system with pulleys and spring tension to grant the user a mechanical advantage. We’re not exactly sure what to call [Zünder’s] bow design. He shared his unconventional take on a DIY bow that uses coiled springs as well as some other unique features.

Toothbrush heads and 3D printing make an enclosed, bristle-supported arrow rest.

What we really dig about [Zünder]’s design is how easy it is to grasp how it all works. As he demonstrates using the bow, the way the levers, pulleys, and spring tension all work together is very clear. The 3D-printed quiver and arrow rest are nice added touches, and we especially love the use of three toothbrush heads to provide contained support for a nocked arrow. The ring of bristles are sturdy enough to easily support the shaft, and don’t interfere with the arrow’s fletching.

[Zünder] has a photo gallery with a few additional photos and closeups, and you can watch him demonstrate his bow in the video embedded below.

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FM Radio From Scratch Using An Arduino

December 4, 2020 by Bryan Cockfield 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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Full 8-Bit Computer On Breadboards

November 23, 2020 by Bryan Cockfield 13 Comments

Getting into a big electronics project often involves the use of specialized tools, namely the use of some sort of soldering iron or other way to apply solder to often intricate, tiny, and heat-sensitive parts. While it’s best to learn to pick up this skill at some point, it’s not always necessary, even for big, complicated projects like [DerULF1]’s full 8-bit computer that he built entirely on breadboards.

For a fully featured 8-bit computer, this build goes deep into the details of how the computer works. The clock allows programs to be stepped through one cycle at a time, and even the memory can be individually accessed with a set of switches. There are plenty of other interesting features as well, such as using registers to access extra memory. It features an SPI port and PS/2 keyboard controller and also loads programs from an SD card.

The build was inspired by some of [Ben Eater]’s projects which famously focus on using logic gates and TTL chips to perform complex tasks, such as another breadboard computer which plays snake on a small display. It’s certainly a great way to learn about the inner function of computers, and better still that no soldering is required. But you may need a few extra breadboards.

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Improved Flexible Build Plate For SLA Is Ready To Rock

October 26, 2020 by Donald Papp 25 Comments

The Elegoo Mars is an affordable SLA (resin-based) 3D printer, and there are probably few that have seen more mods and experimentation than [Jan Mrázek]’s machine. The final design of his DIY flexible build plate is a refinement of his original proof of concept, which proved a flexible build platform can be every bit as useful on an SLA printer as it is for FDM; instead of chiseling parts off a rigid build platform, simply pop the flexible steel sheet off the magnetic base and flex it slightly for a much easier part removal process. His original design worked, but had a few rough edges that have since been ironed out.

We love how [Jan] walks through all of the design elements and explains what worked and what didn’t. For example, originally he used a galvanized steel sheet which was easy enough to work with, but ended up not being a viable choice because once it’s bent, it stays bent. Spring steel is a much better material for a flexible build platform, but is harder for a hobbyist to cut.

Fortunately, it’s a simple job for any metal fabrication shop and [Jan] got a variety of thicknesses cut very cheaply. It turns out that the sweet spot is 0.3 mm (although 0.2 mm is a better choice for particularly fragile parts.) [Jan] also suggests cutting the sheet a few millimeters larger than the build platform; it’s much easier to peel the sheet off the magnetic base when one can get a fingertip under an edge, after all.

The magnetic base that the steel sheet sticks to is very simple: [Jan] converted a stock build platform by mounting an array of 20 x 20 x 1 mm magnets with 3M adhesive mounting tape. He was worried that resin might seep in between the magnets and cause a problem, perhaps even interfering with the adhesive; but so far it seems to be working very well. Resin is viscous enough that it never penetrates far into the gaps, and no effect on the adhesive has been observed so far.

Watch how easily parts are removed in the short video embedded below, in which [Jan] demonstrates his latest platform design.

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3D Printering: Wash Parts Better And Make Solvent Last Longer

October 6, 2020 by Donald Papp 21 Comments

SLA printing in resin is great, but part washing can be a hassle. The best results come from a two-stage wash, but that also means more material and more processing steps. Fortunately, there are ways to make it easier and more effective. One such way is to use a part washing machine, and I’ll cover a DIY option to make your own, but despite what the advertising implies for the commercial ones, a wash machine isn’t a cure-all.

Let’s go through how to get the best results from part washing, how to make the solvent last as long as possible, and how to dispose of the eventual waste.

Resin-Printed Parts Need Washing

All parts printed in resin emerge from the printer coated in syrupy, uncured goop. This needs to be removed completely, or the print ends up sticky and no amount of drying or additional UV curing will change that. (There is a way to fix sticky prints, but it’s better to avoid the situation in the first place.)

Simple part washing can be done with nothing more than a jar in which to rinse and soak a small part for about ten minutes, but agitation and a secondary wash will go a long way toward better and more consistent results. As mentioned, part washing machines like to present themselves as a one-appliance solution, but best results still come from a two-stage wash, and that means some additional steps.

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This DIY Drill Press Is Very Well Executed

September 22, 2020 by Bryan Cockfield 22 Comments

Plenty of projects we see here could easily be purchased in some form or other. Robot arms, home automation, drones, and even some software can all be had with a quick internet search, to be sure. But there’s no fun in simply buying something when it can be built instead. The same goes for tools as well, and this homemade drill press from [ericinventor] shows that it’s not only possible to build your own tools rather than buy them, but often it’s cheaper as well.

This mini drill press has every feature we could think of needing in a tool like this. It uses off-the-shelf components including the motor and linear bearing carriage (which was actually salvaged from the Z-axis of a CNC machine). The chassis was built from stock aluminum and bolted together, making sure to keep everything square so that the drill press is as precise as possible. The movement is controlled from a set of 3D printed gears which are turned by hand.

The drill press is capable of drilling holes in most materials, including metal, and although small it would be great for precision work. [ericinventor] notes that it’s not necessary to use a separate motor, and that it’s possible to use this build with a Dremel tool if one is already available to you. Either way, it’s a handy tool to have around the shop, and with only a few modifications it might be usable as a mill as well.

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