Unique Seven-Segment Display Relies On FR-4 Fluorescence

October 16, 2021 by Dan Maloney 11 Comments

It’s interesting what you see when you train a black light on everyday objects. We strongly suggest not doing this in a hotel room, but if you shine UV light on, say, a printed circuit board, you might see what [Sam Ettinger] did, which led him to build these cool low-profile seven-segment fluorescent PCB displays.

As it turns out, at least some FR-4 PCBs fluoresce under UV light, giving off a ghostly blue-green glow. Seeing the possibilities, [Sam] designed a PCB with cutouts in the copper and solder mask in the shape of a traditional seven-segment display. The backside of the PCB has pads for UV LEDs and current-limiting resistors, which shine through the board and induce the segments to glow. Through-slots between the segments keep light from one segment from bleeding over into the next; while [Sam] left the slots unfilled, they could easily be filled with solder. The fluorescent property of FR-4, and therefore the brightness and tint of the segments, seems to vary by board thickness and PCB manufacturer, but it looks like most PCBs will show pretty good results.

We’d say the obvious first improvement might be to cover the back of the display with black epoxy, to keep stray light down, and to improve contrast. But they look pretty great just as they are. We can also see how displays with other shapes, like icons and simple symbols. Or maybe even alphanumeric characters — say, haven’t we seen something like that before?

Here’s A 100 MHz Pin-Compatible 6502 Replacement

October 15, 2021 by Lewin Day 94 Comments

The MOS Technology 6502 CPU was a popular part in its day. In various modified versions, it powered everything from the Commodore 64 to the Nintendo Entertainment System, and showed up in a million other applications too. A popular variant is the 65C02, and [Jürgen] decided to whip up a pin-compatible FPGA version that runs at a blazing 100MHz.

The CPU core was borrowed from work by [Arlet Ottens] and extended with 65C02 functionality by [Ed Spittles] and [David Banks]. [Jürgen] then packaged that core in a Spartan-6 FPGA and placed it on a small PCB the size of the original 65C02’s 40-pin dual inline package.

The FPGA is set up to access the external CPU bus with the timing matched to the clock of the host machine. However, internally, the CPU core runs at 100MHz. It copies RAM and ROM from the host machine into its own internal 64 kilobyte RAM, minus the areas used for memory-mapped I/O by the host. The CPU then runs at full 100MHz speed except when it needs to talk to those I/O addresses.

It allows the chip to accelerate plenty of tasks without completely flipping out when used with older hardware that can’t run at anywhere near 100MHz. The pin-compatible design has been tested successfully in an Apple II and a Commodore 8032, as well as a variety of vintage chess computers.

We’ve seen the opposite before too, with a real 6502 paired with a FPGA acting as the rest of the computer. If you’ve got any cutting-edge 6502 hacks of your own (not a misprint!), let us know!

[Thanks to David Palmer for the tip]

Electroplating Carbon Fibers Can Have Interesting Results

October 15, 2021 by Lewin Day 17 Comments

Typically, electroplating is used to put coatings of one metal upon another, often for reasons of corrosion protection or to reduce wear. However, other conductive materials can be electroplated, as demonstrated by [Michaɫ Baran].

Finer details are sparse, but [Michaɫ’s] images show the basic concept behind producing a composite metal material hand sculpture. The initial steps involve 3D printing a perforated plastic shell of a hand, and stuffing it with carbon fibers. It appears some kind of plastic balls are also used in order to help fill out the space inside the hand mold.

Then, it’s a simple matter of dunking the plastic hand in a solution for what appears to be copper electroplating, with the carbon fiber hooked up as one of the electrodes. The carbon fibers are then knitted together by the copper attached by the electroplating process. The mold can then be cut away, and the plastic filling removed, and a metal composite hand is all that’s left.

[Michaɫ] has experimented with other forms too, but the basic concept is that these conductive fibers can readily be stuffed into molds or held in various shapes, and then coated with metal. We’d love to see the results more closely to determine the strength and usefulness of the material.

Similar techniques can be used to strengthen 3D printed parts, too. If you’ve got your own ideas on how to best use this technique, sound off below. If you’ve already done it, though, do drop us a line!

[Thanks to Krzysztof for the tip]

Hack Your Sodastream With A Giant CO2 Canister

October 14, 2021 by Lewin Day 110 Comments

Sodastream machines are popular amongst people who like to make their own seltzer water at home. However, replenishing the tiny gas canisters is expensive and wasteful. [Becky] decided to upgrade her machine to avoid this problem, and added some smarts while she was at it.

The simple part of the hack is using an adapter to connect the Sodastream apparatus to a 50 lb CO2 tank from the welding store. This is easy enough, and just uses a off the shelf adapter. Using welding-grade gas in your drinking water is probably a really bad idea, but [Becky] was willing to take the nisk.

However, safety was given due attention in that a CO2 monitor was installed to make [Becky] aware of any dangerous leaks. The tank is also placed on a custom scale built with load cells and an ESP8266, which allows monitoring of how much gas is left. [Becky] notes that at her rate of drinking one bottle a day, the tank should last her a full 7 years or so.

The project brings costs down to 18 cents per liter of seltzer, versus 38 cents for the Sodastream gas supply. It’s likely that the Sodastream prices could still be beat even if a food-safe CO2 source was used. Plus, there’s no need to regularly buy new bottles!

Overall, it’s a great project and one that recalls us of continuous-ink printer hacks. Video after the break.

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A 3D-printed scale model of the mechanism inside a grand piano.

Printed Piano Mechanism Sure Is Grand

October 14, 2021 by Kristina Panos 9 Comments

Do you know how a piano works? Sure, you press a key and a hammer strikes a string, but what are the finer points of this operation? The intricacy of the ingenious mechanism is laid bare in [Mechanistic]’s 3D-printed scale model of a small section of the grand piano keyboard. The ‘grand’ distinction here is piano length-agnostic and simply refers to any non-upright. Those operate the same way, but are laid out differently in order to save space.

The keys of an acoustic piano are much longer than just the part that shows — they are long levers that do a lot of work, including working their own sound dampeners. The really interesting part is the mechanism that allows a note to be played repeatedly without first releasing the key. This same mechanism also lets the pianist play softly, loudly, or somewhere in between based on the amount of pressure applied.

So you know that the hammer strikes the string (or in this case, the rod), and you can probably figure that it backs off to let the string ring out. But there’s also this whole system that keeps the hammer close by for repeated strikings, as long as the person is holding down the key. Be sure to check it out in the build video after the break.

[Mechanistic] must be going for the standing ovation, because they say in the video’s comments that they will release STL files when they’re finished writing the assembly guide (!). What an encore that will be.

There are many ways to hack an acoustic piano, but don’t go thinking you can sub in guitar strings.

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Hacking An IKEA Lampshade Into A Stunning Dichroic Lamp

October 14, 2021 by Lewin Day 6 Comments

Often, when we see a colorful lamp project, it’s something that makes use of RGB LEDs and all manner of lovely animations and fading effects. This project from [Raymond Power] features beautiful shifting colors, but foregos fancy LEDs for the magic of dichroic film.

Dichroic films work with thin-film interference, with the wavelength of light passed through the film changing depending on the angle of incidence. Thus, as the observer’s viewing angle changes, the apparent color of the film changes, too. It creates particularly beautiful effects when several layers of film are laid on top of each other.

[Raymond] happened to source some of this film from a fancy IKEA lampshade. At the time, he’d been experimenting with folding paper cubes and similar constructions, and decided to meld the two ideas.

The result was a cubic dichroic lampshade, which looks truly fantastic. Sitting on top of a simple white LED light, the structure lights up with a rich blend of complementary and shifting colors.

It’s a beautiful thing, and something we’d love to have in our own home. Dichroic materials find themselves being used in some more scientific uses, too. Video after the break.

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Homebrew Circuit Explores The Mysteries Of Analog-to-Digital Conversion

October 8, 2021 by Dan Maloney 9 Comments

When it comes to getting signals from an analog world into our computers, most of us don’t give much thought to how the hardware that does the job works. But as it turns out, there are a number of ways to skin the analog to digital conversion cat, and building your own homebrew successive approximation register ADC is a great way to dispel some of the mystery.

From his description of the project, it’s clear that [Mitsuru Yamada] wasn’t looking to build a practical ADC, but was more interested in what he could learn by rolling his own. A successive approximation register ADC works by quickly cycling through all possible voltage levels in its input range, eventually zeroing in on the voltage of the input signal at that moment and outputting its digital representation. The video below shows how the SAR ADC works visually, using an oscilloscope to show both the input voltage and the output of the internal R-2R DAC. The ADC has an input range of 0 V to 5 V and seven bits of resolution and uses nothing but commonly available 74xx series logic chips and a couple of easily sourced analogs for the sample-hold and comparator section. And as usual with one of his projects, the build quality and workmanship are impeccable.

We love these sorts of projects, which are undertaken simply for the joy of building something and learning how it works. For more of [Yamada-san]’s projects, check out his 6502-based RPN calculator, or the serial terminal that should have been.

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