Building A Front Panel For The RC2014 Computer

November 21, 2019 by 6 Comments

The RC2014 is a slick Z80 computer kit that’s graced these pages a number of times in the past. It allows anyone with a soldering iron and a USB-to-serial adapter to experience the thrill of early 1980s desktop computing. But what if you’re looking for an even more vintage experience? In that case, this custom RC2014 front panel from [James Stanley] might be just the thing to scratch that Altair itch.

The front panel allows you to view and alter the contents of memory with nothing more complex than toggle switches and LEDs, just like on the early microcomputers of the 1970s. If you’ve ever wanted to learn how a computer works on the most basic level, single-stepping through instructions and reading them out in binary is a great way to do it.

[James] says he was inspired to take on this project after reading a 1978 issue of Kilobaud Magazine (as one does), and seeing an article about building a homebrew Z80 machine with a front panel. Obviously he had to modify the approach a bit to mate up with this relatively modern variation on the venerable CPU, but the idea was essentially the same.

His documentation for the project is sure to be fascinating for anyone enamored with those iconic computers of yesteryear, but even readers with more modern sensibilities will likely find some interesting details. The way [James] coaxes the data and various status states out of the kit computer takes up the bulk of the write-up, but afterwards he talks about how he designed the PCB and wraps up with his tips for creating a professional looking front panel.

This isn’t the first time we’ve seen a modern Z80 computer kitted out with blinkenlights, but it’s certainly one of the most professional looking. If you combine the RC2014 kits available on Tindie with the details provided by [James], you’ll soon be learning the fine art of programming a computer with toggle switches.

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Casting Gears At Home

November 21, 2019 by 45 Comments

Automatic doors and gates are great, except when they fail, which seems to be about every three days in our experience. [MAD WHEEL] had just such a failure, with a plastic gear being the culprit. Rather than buy a new drive unit, they set about casting a replacement in metal.

The video is light on instructions and heavy on progressive rock, and may be a little difficult to follow for beginners. The process begins by gluing the original plastic part back together, and filling in the gaps with epoxy putty. A mould is then created by setting the gear in a gelatine/glycerine mixture. This mould is then filled with wax to create a wax copy of the original part. The wax gear is fitted with cylindrical stems to act as runners for molten metal, and then a plaster mould is made around the wax positive. Two plaster moulds are made, which are placed in an oven to melt out the wax.

The aim was to cast a replacement part in aluminium. The first attempt failed, with the aluminium cooling too rapidly. This meant fine details like the gear teeth simply didn’t cast properly, creating a useless metal blob. On the second attempt, the plaster mould was heated first, and this kept things hot enough to allow the aluminium to fill in the finer details. With that done, it was a simple matter of some post-processing to remove the runners, clean up the gear teeth and refine the shape of the gear on the lathe.

The resulting part does its job well, meshing properly with the other gears in the drivetrain and moving the gate effectively. Many in the comments have stated that the original gear being plastic was likely as a safety measure, to strip out in the event the gate is jammed. While this may be true, it’s a far more robust design practice to instead use a breakable plastic key rather than breaking an entire gear in the event of a problem.

Casting is quite accessible to the dedicated home maker. It’s a great way to make custom metal parts once you’ve learned the fundamentals! Video after the break.

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Little Flash Charges In 40 Seconds Thanks To Super Capacitors

November 21, 2019 by 10 Comments

We’ve all committed the sin of making a little arduino robot and running it off AA batteries. Little Flash is better than that and runs off three 350 F capacitors.

In fact, that’s the entire mission of the robot. [Mike Rigsby] wants people to know there’s a better way. What’s really cool is that 10 A for 40 seconds lets the robot run for over 25 minutes!

The robot itself is really simple. The case is 3D printed with an eye towards simplicity. The brains are an Arduino nano and the primary input is a bump sensor. The robot runs around randomly, but avoids getting stuck with the classic reverse-and-turn on collision.

It’s cool to see how far these capacitors have come. We remember people wondering about these high priced specialty parts when they first dropped on the hobby scene, but they’re becoming more and more prevalent compared to other solutions such as coin-cells and solder tab lithium batteries for PCB power solutions.

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Retrotechtacular: 934 MHz CB Radio

November 21, 2019 by 49 Comments

The radio spectrum is carefully regulated and divided up by Governments worldwide. Some of it is shared across jurisdictions under the terms of international treaties, while other allocations exist only in individual countries. Often these can contain some surprising oddities, and one of these is our subject today. Did you know that the UK’s first legal CB radio channels included a set in the UHF range, at 934 MHz? Don’t worry, neither did most Brits. Behind it lies a tale of bureaucracy, and of a bungled attempt to create an industry around a barely usable product.

Hey, 2019, Got Your Ears On?

Did this car make you want a CB radio? Stuurm [CC BY-SA 3.0]
Did this car make you want a CB radio? Stuurm [CC BY-SA 3.0]
Mention CB radio in 2019 it’s likely that the image conjured in the mind of the listener will be one from a previous decade. Burt Reynolds and Jerry Reed in Smokey and the Bandit perhaps, or C. W. McCall’s Convoy. It may not be very cool in the age of WhatsApp, but in the 1970s a CB rig was the last word in fashionable auto accessories and a serious object of desire into which otherwise sane adults yearned to speak the slang of the long-haul trucker.

If you weren’t American though, CB could be a risky business. Much of the rest of the world didn’t have a legal CB allocation, and correspondingly didn’t have access to legal CB rigs. The bombardment of CB references in exported American culture created a huge demand for CB though, and for British would-be CBers that was satisfied by illegally imported American equipment. A vibrant community erupted around UK illegal 27 MHz AM CB in the late 1970s, and Government anger was met with campaigning for a legal allocation. Brits eventually got a legal 27 MHz allocation in November 1981, but the years leading up to that produced a few surprises.

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Gaze Deeply Into These Infinity Mirror Coasters

November 21, 2019 by 11 Comments

Infinity mirrors have been gaining in popularity recently, thanks in no small part to the availability of low-cost RGB LED strips to line them with. Generally such pieces are limited to wall art, or the occasional table build, which is what makes these infinity mirror drink coasters from [MnMakerMan] so unique.

Built from an ATtiny85 and a WS2812B LED strip nestled into a 3D printed enclosure, these coasters are relatively cheap and easy to assemble should you want to run a few off before the holiday party season. [MnMakerMan] mentions the LEDs can consume a decent amount of energy, so he’s included a module to allow recharging of the internal 3.7 V 1500 mAh battery over USB.

Of course, a couple of PLA pieces and a custom PCB doesn’t make an infinity mirror. To achieve the desired effect, he’s created a stack consisting of a 4″ glass mirror, a 1/8″ thick plexiglass disc, and one-way mirror tint film. The WS2812B strip mounted along the circumference lights up the void between the two surfaces, and produces a respectable sense of depth that can be seen in the video after the break.

This isn’t the first high-tech piece of surface protection we’ve seen around these parts, as some very nice wirelessly charged supercapacitor coasters were entered into the 2019 Hackaday Prize. Of course, if you’re of the opinion that coasters should remain as cheap as possible, we’ve seen a number of automated attempts to add some flair to the classic paperboard discs.

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Training Bats In The Random Forest With The Confusion Matrix

November 21, 2019 by 4 Comments

When exploring the realm of Machine Learning, it’s always nice to have some real and interesting data to work with. That’s where the bats come in – they’re fascinating animals that emit very particular ultrasonic calls that can be recorded and analysed with computer software to get a fairly good idea of what species they are. When analysed with an FFT spectogram, we can see the individual call shapes very clearly.

Nyctalus noctula (noctule bat)
Myotis nattereri (natterera’s bat)
Plecotus auritus (brown long eared)
Pipistrellus pipistrellus (common pipistrelle)

Creating an open source classifier for bats is also potentially useful for the world outside of Machine Learning as it could not only enable us to more easily monitor bats themselves, but also the knock on effects of modern farming methods on the natural environment. Bats feed on moths and other night flying insects which themselves have been decimated in numbers. Even in the depths of the countryside here in the UK these insects are a fraction of the population that they used to be 30 years ago, but nobody seems to have monitored this decline.

So getting back to our spectograms, it would be perfectly reasonable to throw these images at a convolutional neural network (CNN) and use an image feature-recognition strategy. But I wanted to explore the depths of the mysterious Random Forest. Continue reading “Training Bats In The Random Forest With The Confusion Matrix” →

Jackpot!: The Trials And Tribulations Of Turning A Slot Machine Into An ATM

November 21, 2019 by 15 Comments

Have you ever wished that slot machines dispensed money as easily as an ATM? Well so did [Scotty Allen] from Strange Parts, so in collaboration with his friend [Matt] decided to combine the two. After a four-month journey fraught with magic smoke and frustration, they managed to build a fully functional ATM slot machine.

The basic idea is that you insert your card and enter your pin like on a normal ATM, select your winning amount, and pull the lever. This sets wheels spinning, which come to a stop with three-of-a-kind every time, and you win your own money as a bucket load of coins with all the accompanying fanfare. The project took way longer than [Scotty] expected, and he ended up missing his original deadline to show off the machine at DEF CON.

They started with an old broken Japanese slot machine, and replaced the control board with an Arduino Due after a lot of reverse engineering and hacking. [Scotty] did a cool video just on getting the original vacuum fluorescent display working. Integrating the ATM parts proved to be the biggest challenge, with number of very expensive parts releasing their magic smoke or getting bricked in the process. [Scotty] came up with an ingeniously simple hack to interface the ATM hardware with the Arduino. The cash note dispenser uses multiple sensors to detect if there are notes loaded and if one is successfully dispensed. These were spoofed by the Arduino, which controls two coin hoppers instead to dispense appropriate amount of quarters or pennies. The build was rounded off with some very neat custom graphics on the glass panels, and the machine was finally showed off at a local arcade.

This was an awesome project, and we can appreciate the fact that [Scotty] made no attempt to hide the real emotional roller coaster that anyone who has worked on a large project knows, but is rarely documented in logs. [Scotty] has made a name for himself by building his own iPhone from parts and touring Shenzhen’s many factories. Check out the videos after the break Continue reading “Jackpot!: The Trials And Tribulations Of Turning A Slot Machine Into An ATM” →