Hacking A Cheap EBay Frequency Counter

April 30, 2019 by Lewin Day 5 Comments

eBay is a wondrous land, full of Star Wars memorabilia in poor condition, old game consoles at insane markups, and a surprising amount of DIY electronics. [TheHWCave] found himself tinkering with a common frequency counter kit, and decided to make a few choice improvements along the way (Youtube link, embedded below).

The frequency counter in question is a common clone version of [Wolfgang “Wolf” Büscher]’s minimalist PIC design. Using little more than a PIC16F628 and some seven-segment displays, it’s a competent frequency counter for general use. Clone versions often add a crystal oscillator tester and are available on eBay for a fairly low price.

[TheHWCave] found that the modifications were less than useful, and developed a way to turn the tester components into a more useful signal preamp instead. Not content to stop there, custom firmware was developed to both improve the resolution and also add a tachometer feature. This allows the device to display its output in revolutions per minute as opposed to simply displaying in hertz. By combining this with an optical pickup or other RPM signal, it makes a handy display for rotational speed. If you’re unfamiliar with the theory, read up on our phototachometer primer. If you’re looking to modify your own kit, modified firmware is available on Github.

We’ve seen other eBay kit specials modified before. Being cheap and using commodity microcontrollers makes them a ripe platform for hacking, whether you just want to make a few tweaks or completely repurpose the device.

[Thanks to Acesoft for the tip!]

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3D Printing A Lifting Body Aircraft

April 29, 2019 by Lewin Day 17 Comments

When you think of unconventional aircraft, flying wings have had plenty of time in the sun over the last few decades. With striking designs like the B-2 Spirit and F-117A Nighthawk on the flight line, it’s no surprise. The lifting body never really caught on, however, and it languishes in ignominy to this day. Despite their obscurity, [rctestflight] decided to 3D print a few lifting bodies for himself and take them out for a field test (YouTube video, embedded below).

Most aircraft have a body designed with low drag, and wings designed to provide lift. Lifting body aircraft focus the body design on providing that lift and often have no real wing to the design, needing only control surfaces to compliment the body. For this project, several different designs were constructed, with the craft being drop-launched from a multirotor at significant altitude. Initial tests were hamstrung by stability problems, both due to center of gravity issues and uncertain aerodynamic phenomena. The early designs were particularly prone to suddenly entering an unrecoverable flat spin. Later modifications included the addition of further stabilizers, which helped performance somewhat.

3D printing is a great way to experiment with aerodynamic phenomena, as it’s easy to create all manner of complicated geometries to tinker with. [rctestflight] has done solid work developing a basic craft, and we’d love to see the work continue with powered tests and more development. If flying wings are more your jam, though, you can 3D print those too. Video after the break.

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Electromechanical YouTube Sub Counter Trades Clicks For Clacks

April 28, 2019 by Kristina Panos 11 Comments

Acquiring a new YouTube subscriber is a blessed event that deserves far more fanfare than a phone notification. But maybe blinkenlights don’t really do it for you anymore, or you simply prefer to be soothed sonically rather than visually. Well, what could be more satisfying than the crisp clack of an electromechanical 7-segment display? Six of them, of course. These things look great, they sound great, and once they’re set, they don’t need power to stay that way.

These displays switch between black and white by reversing current flow through their electromagnets, so [Zack] turned to the H-bridge in order to use them with DC. One H-bridge for each segment of six displays adds up fast, though. To get around this, [Zack] tied one pole of each electromagnet together for a common signal input, and used the other pole to control each segment individually. Then, he was able to tie all the A segments together, all the B segments, and so on, and only needs 13 H-bridges to do it all.

There was just one thing [Zack] didn’t count on. Once he got the board soldered up and running, the displays started acting funny. The low impedance of the coils was causing them to influence each other over the common path, so he added diode arrays to keep them in line.

[Zack]’s using an ESP32 to get the 411 through the Google API, and four octal serial switches to drive the displays. Even more satisfying than all those clacks is the displays’ operational economy baked into [Zack]’s code—as they count up, any segments common to the first digit and the next digit remain on. Increment your way past the break to check out the build video.

Not focused on numbers, but still want to celebrate each new sub? Try a dancing robot or a Tetris twist.

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The No-CPU Computer Gets A C Compiler

April 26, 2019 by Brian Benchoff 24 Comments

C is the most perfect language and it will run on anything. It will even run on a computer without a CPU.

The computer in question here is the Gigatron, a fully-functional ‘home computer’ the likes of which you would find in the late 70s and early 80s, complete with a VGA output. What makes the Gigatron exceptional is the fact that there is no microprocessor; everything is just a RAM, a ROM, and a bunch of logic chips. There is no ALU chip. Or rather, there is; it’s just that an entire RISC CPU is implemented in basic logic chips and a whole lot of microcode on the ROM. It’s weird, yes, but it is cool. We’ve taken a look at the Gigatron before, and with this computer you get a glimpse of how clever engineers could have been if there were massive memories available in the late 70s.

While the Gigatron can be programmed in BASIC, the limiting factor of this computer is the fact that it remains exceptionally difficult to program. This is what the 8-Bit Guy says, and even though you can write some simple programs, it’s nothing compared to the likes of an Apple II or C64. If only there were a proper IDE, indeed if only there were a C compiler. That’s where [pgavlin] comes in. He has the LCC compiler working on the Gigatron. This is technically a C compiler for a computer without a CPU, or a computer that is entirely CPU. Either way you look at it, this is impressive.

As far as examples and demos go, [pgavlin] has a demo of Conway’s Game of Life working, and a program that will put dots on the screen. It’s not much, and it’s very slow, but check out the video below.

This isn’t a complete implementation of C, as multiplication, division, mod, and arbitrary shifts left or right haven’t been written yet. Floating point support will probably never be completed, and there’s no shame in that. The hardware is limited due to the fact of the fragmented memory map, but this can be improved by upgrading the Gigatron to a 64k memory model.

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Reviving A Casio Scientific Calculator, With A CNC Router

April 26, 2019 by Dan Maloney 6 Comments

Before Wolfram Alpha, before the Internet, before even PCs, calculations more complex than what could be accomplished with a “four banger” required some kind of programmable calculator. There were many to choose from, if you had the means, and as time passed they became more and more sophisticated. Some even added offline storage so your painstakingly written and tediously entered programs didn’t evaporate when the calculator was turned off.

One such programmable calculator, a Casio PRO fx-1 with magnetic card storage, came across [amen]’s bench recently. Sadly, it didn’t come with any cards, so [amen] reverse engineered the card reader and brought the machine back to its 1970s glory. The oddball mag cards for it are no longer available, so [amen] had to make do with. He found some blank cards of approximately the right size for cheap, but somehow had to replicate the band of vertical stripes adjacent to the magnetic strip on the card. Reasoning that they provide an optical synchronization signal, he decided to use a CNC router to cut a series of fine-pitched slots in the plastic card. It took a little effort to get working, including tapping the optical sensor and reading the signal on an oscilloscope, but as the video below shows, the hacked cards work fine with the vintage calculator.

Kudos to [amen] for reviving this retro-cool calculator. Now that it’s back in action, it might be fun to visualize domains on the magnetic strip. A flatbed scanner can be used for that job.

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House Training A Military TA-1024A Field Telephone

April 24, 2019 by Tom Nardi 11 Comments

After spotting some interesting military phones at a museum, [CuriousMarc] wondered what it would take to retrofit these heavy duty pieces of telecom equipment for civilian use. He knew most of the internals would be a lost cause, but reasoned that if he could reverse engineer key elements such as the handset and keypad, he might be able to connect them to the electronics of a standard telephone. Luckily for us, he was kind enough to document the process.

There were a number of interesting problems that needed to be solved, but the first and perhaps largest of them was the unusual wiring of the keypad. It wasn’t connected in the way modern hackers like us might expect, and [CuriousMarc] had to end up doing some pretty significant rewiring. By cutting the existing traces on the PCB with a Dremel and drilling new holes to run his wires around the back, he was able to convert it over to a wiring scheme that contemporary touch tone phones could use.

An adapter needed to be fabricated to mount a basic electret microphone in place of the original dynamic one, but the original speaker was usable. He wanted to adapt the magnetic sensor that detected when the handset was off the hook, but in the end it was much easier to just drill a small hole and use a standard push button.

The main board of the phone is a perfect example of the gorgeous spare-no-expense construction you’d expect from a military communications device, but unfortunately it had to go in the bin. In its place is the guts of a lowly RCA phone that was purchased for the princely sum of $9.99. [CuriousMarc] won’t be able to contact NORAD anymore, but at least he’ll be able to order a pizza. The red buttons on the keypad, originally used to set the priority level of the call on the military’s AUTOVON telephone network, have now been wired to more mundane features of the phone such as redial.

While this is fine for a one-off project, we’d love to see a drop-in POTS or VoIP conversion for these phones that didn’t involve so much modification and rewiring. Now that we have some documentation for things like the keypad and hook sensor, it shouldn’t be hard to take their idiosyncrasies into account with a custom PCB. Dragging vintage gear into the modern era is always a favorite pastime for hackers, so maybe somebody out there will be inspired to take on the challenge.

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Texting With A Teletype

April 23, 2019 by Brian Benchoff 13 Comments

How do you get the kids interested in old technology? By connecting it to a phone, obviously. Those kids and their phones. When [Marek] got his hands on an old-school teletype, he hooked it up to a GSM network, with all the bells and whistles including a 40mA current loop running at an impressive 50 baud.

The teletype in question here is a vintage T100 teletype manufactured in Czechoslovakia sometime in the ’70s. This was a gift to [Marek]’s workplace, the museum of Urban Engineering in Cracow, and this project is effectively an experiment to investigate the possibility of running this teletype as an interactive exhibit rather than an artefact from the age of current loops and phone systems.

The current loop is, or was, the standard way of connecting a teletype to anything, so all [Marek] had to do was construct a box that translated the signals from a GSM modem to this current loop. For the prototype, the microcontroller in question is an old AT89C2051 (as that’s what was sitting in the parts drawer). This was moved over to a PIC32 microcontroller and a SIM800 GSM module. This is housed in a two-part enclosure, with the GSM interfaced housed in one half, with the current loop generator consisting of a simple DC power supply housed int the other half.

This interface is capable of receiving and sending messages from the keyboard to a GSM network, so it is theoretically possible you could text your friends using an old-school teletype. This functionality hasn’t been implemented yet, but it is just about the coolest thing you could possibly imagine. You can check out a video of the teletype in action below. Continue reading “Texting With A Teletype” →