Chaining Together A 16×2 Bubble LED Display

December 10, 2019 by Tom Nardi 27 Comments

We’ve recently noticed an uptick of interest in so-called “bubble displays”: vintage alphanumeric LEDs which are probably best remembered as being used in watches and calculators before the LCD took over. Today they’re available as surplus or even salvage for literally pennies, but unfortunately they only provide four or five characters to work with. Or rather they did, until [sjm4306] built a board that chains them into a 16×2 array.

For the princely sum of 71 cents each, [sjm4306] picked up ten HPDL-1414 displays, each capable of showing four characters. He then designed a PCB that would accept eight of the displays at once, and even thought ahead to use headers so they could be pulled out and swapped as needed. Of course mounting them is only half the battle, you still need to drive the things.

Each display has its own dedicated driver chip on board, but trying to address each one individually would take far too many pins. So [sjm4306] opted to use a trio of 74HC595 shift registers, allowing him to toggle the three dozen pins necessary over SPI from a microcontroller. He’s even written up a little library and some example code that you can grab on the project’s Hackaday.io page.

Unfortunately, after all his hard work, tragedy struck. As these displays were a couple decades old given their date code, [sjm4306] thought he would clean them up with a bit of alcohol before their big video debut. But whatever plastic the clear panels are made of didn’t take kindly to the IPA, and they all shattered. They still work, but it’s definitely a quirk to keep in mind if you pick up some of these vintage displays to play with yourself.

In the past we’ve seen a much smaller PCB that allowed similar displays to more easily be interfaced with modern microcontrollers; perfect if you just want to bang out a few retro LED characters with a minimum of fuss.

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Teardown: 168-in-1 Retro Handheld Game

December 9, 2019 by Tom Nardi 33 Comments

The holidays are upon us, and that can mean many furrowed brows trying to figure out what token gift they can give out this year as stocking-stuffers. Something that’s a bit more interesting than a coupon book or a lotto scratcher, but also affordable enough that you can buy a few of them without having to take part in that other great holiday tradition: unnecessary credit debit.

Includes the NES classic *Super Militarized Police Bros 3*

Which is how I came to possess, at least temporarily, one of these cheap handheld multi-games that are all over Amazon and eBay. The one I ordered carries the brand name Weikin, but there are dozens of identical systems available, all being sold at around the same $20 USD price point. With the outward appearance of a squat Game Boy, these systems promise to provide precisely 168 games for your mobile enjoyment, and many even include a composite video out cable and external controller for the less ambulatory classic game aficionado.

At a glance, the average Hackaday reader will probably see right through this ploy. Invariably, these devices will be using some “NES on a Chip” solution to emulate a handful of legitimate classics mixed in with enough lazy ROM hacked versions of games you almost remember to hit that oddly specific number of 168 titles. It’s nearly a foregone conclusion that at the heart of this little bundle of faux-retro gaming lies a black epoxy blob, the bane of hardware tinkerers everywhere.

Of course, there’s only one way to find out. Let’s crack open one of these budget handhelds to see what cost reduction secrets are inside. Have the designers secured their place on the Nice List? Or have we been sold the proverbial lump of coal?

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Guitar Effect Built From An Old Record Player

December 9, 2019 by Tom Nardi 4 Comments

With little more than a gutted record player, a light bulb, and the legendary 555 timer IC, [Jacob Ellzey] has constructed this very slick optical tremolo effect for his guitar. By modulating the volume of the input signal, the device creates the wavering effect demonstrated in the video after the break.

The key is a vinyl record with large tabs cut out of it. As the record spins, these voids alternately block and unblock a small incandescent bulb. A common GL5537 photoresistor, mounted on the arm that originally held the player’s needle, picks up the varying light levels and passes that on to the electronics underneath the deck. An important note here is that different spacing and sizing of the cutouts will change the sound produced by the effect. [Jacob] has already produced a few different designs and plans on experimenting with more now that the electronics are completed.

Under the hood there’s a voltage divider and low gain amplifier connected to the photoresistor, and also a 555 timer circuit that’s driving the incandescent bulb. Once he was done fiddling with them, the circuit was moved to a neat little protoboard. A pair of potentiometers mounted through the side of the record player allow for adjusting the depth of the effect itself, as well as the output volume. Naturally, there’s also an external foot pedal that allows keying the effect on and off without taking your hands from the guitar.

As is usually the case, everything was going well on this project until the final moments, when [Jacob] found that the circuit and bulb were both browning out when powered from the same transformer. As a quick fix, he gutted a Keurig and used its transformer to drive the light bulb by itself. With independent power supplies, he was ready to rock.

Of course this isn’t the first time we’ve seen a piece of consumer electronics modified into a guitar effect, but if you’re looking for something a bit more built for purpose, there’s plenty of high-tech options to keep you busy.

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Inkjet Printing On The Cheap With A Continuous Ink System

December 6, 2019 by Lewin Day 39 Comments

Inkjet printers are cheap to buy, but expensive to run. Replacement cartridges can easily cost double the price of the hardware itself, leading many to decry the technology entirely. However, the hackers of the world have the problem licked – enter the continuous ink system.

[cprossu] wanted an affordable color printing solution for the hackerspace. A cheap printer was sourced from a thrift store. The model chosen was selected for its lack of cartridge DRM and the availability of kits on eBay for conversion to a continuous ink system. This involves running large refillable tanks of ink instead of small individual cartridges which must be thrown away when empty.

[cprossu] discusses both the challenges you’ll likely face in a general build, as well as the specific work required to handle the conversion on an Epson Artisan 725. There’s also excessive label-maker abuse, which always brings a smile to our face. It’s a conversion well worth considering if you find yourself regularly purchasing expensive cartridges. We’ve even seen similar builds as far back as 2009, right from the ground up!

Swapping The ROMs In Mini Arcade Cabinets

December 6, 2019 by Tom Nardi 10 Comments

You’ve probably seen a few of these miniature arcade games online or in big box retailers: for $20 USD or so you get scaled-down version of a classic arcade cabinet, perfect for a desk toy or to throw up on a shelf as part of your gaming collection. Like any good Hackaday reader, you were probably curious about what makes them tick. Thanks to [wrongbaud], we don’t have to wonder anymore.

Over the course of several blog posts, [wrongbaud] walks readers through the hardware and software used in a few of these miniature games. For example, the Rampage cabinet is using a so-called “NES on a Chip” along with a SPI flash chip to hold the ROM, while Mortal Kombat is using a Genesis emulation solution and parallel flash. It wouldn’t be interesting if they didn’t throw you a few curves now and again, right?

But these are more than simple teardowns. Once [wrongbaud] gives an overview of the hardware, the next step is reading the respective flash storage and trying to make sense of the dumped data. These sort of games generally reuse the hardware among a number of titles, so by isolating where the game ROM is and replacing it, they can be made to play other games without hardware modification. Here, this capability is demonstrated by replacing the ROM data for Rampage with Yoshi’s Cookie. Naturally it’s one of those things that’s easier said than done, but it’s an interesting proof of concept.

The Mortal Kombat cabinet is a newer addition to the collection, so [wrongbaud] hasn’t progressed quite as far with that one. The parallel flash chip has been dumped with the help of an ESP32 and a MCP23017 I/O expander, and some Genesis ROM headers are identifiable in the data, but there’s still some sifting to be done before the firmware structure can be fully understood.

Even if you’re not in the market for a diminutive arcade experience, the information that [wrongbaud] has collected here is really phenomenal. From understanding protocols such as I2C and SPI to navigating firmware dumps with a hex editor, these posts are an invaluable resource for anyone looking to get started with reverse engineering.

Dub Siren Synth Does It The Old School Way

November 29, 2019 by Lewin Day 18 Comments

There’s little that can compare to the sheer obnoxious thrill of mashing the DJ siren when its your turn behind the decks. We’ve certainly been guilty of abusing the privilege at local house parties, and unsurprisingly have not been invited back. If we ever get another shot, though, we’d be glad to have [lonesoulsurfer]’s dub siren at the ready.

This is a build for the old-school purists. There’s no microcontrollers or digital hardware here. The synth relies on two 555 timer ICs as the oscillators and an LM741 op-amp. These parts harken right back to the dawn of the integrated circuit era, and still do a great job in this application. There’s also a cheap reverb/echo module added in to fatten up the sound. It’s all laced up in an old CB radio enclosure, with the classic woodgrain applique doing much to add to the aesthetic.

It’s a build that’s simple enough for the electronics beginner, and would make a great tactile, analog addition to any DJ’s rig. If you need some wubwubs to go with your woowoos, then consider building a Ball of Dub, too.

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Hacking Transmitters, 1920s Style

November 28, 2019 by Sharon Lin 9 Comments

The origin of the term “breadboard” comes from an amusing past when wooden bread boards were swiped from kitchens and used as a canvas for radio hobbyists to roll homemade capacitors, inductors, and switches. At a period when commercial electronic components were limited, anything within reach was fair game.

[Andy Flowers], call sign K0SM, recently recreated some early transmitters using the same resources and techniques from the 1920s for the Bruce Kelley 1929 QSO Party. The style of the transmitters are based on [Ralph Hartley]’s oscillator circuit built for Bell Telephone in 1915. Most of the components he uses are from the time period, and one of the tubes he uses is even one of four tubes from the first Transatlantic contact in 1923.

Apart from vacuum tubes (which could be purchased) and meters (which could be scrounged from automobiles) [Flowers] recreated his own ferrite plate and outlet condensers for tuning the antennas. The spiderweb coils may not be as common today, but can be found in older Crosley receivers and use less wire than comparable cylindrical coils.

A number of others features of the transmitters also evoke period nostalgia. The coupling to the antenna can be changed using movable glass rods, although without shielding there are quite a number of factors to account for. A vertical panel in the 1920s style also shows measurements from the filament, plate current, and antenna coupling.

While amature radio has become increasingly high-tech over the last few years, it’s always good to see dedicated individuals keeping the old ways alive; no matter what kind of technology they’re interested in.

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