classic hacks

2667 Articles

Parasite ATtiny Resets Your ESP32 For You

May 1, 2019 by 28 Comments

Embedded development can be a tough process. Between weird electrical gremlins, obscure bugs and our own mistakes, it can be a real struggle at times. To keep cognitive loads to a minimum, it’s best to make sure your tools are as simple and easy to use as possible. [tech] got tired of having to push a button to prepare the ESP32 for programming, and decided to solve the problem.

The solution comes via another microcontroller, in this case an ATtiny9. The small device listens in on the ESP32’s serial receiving pin. When it detects the Arduino IDE’s boot sequence on the line, it switches the BOOT0 and RESET lines on the ESP32, emulating the button presses to force it into programming mode.

Once you’ve become accustomed to one-click programming your ESP boards, you’re not going to want to go back. We could imagine this hack being replicated in a tidy piggyback format so it could be moved from board to board as workflow dictates.

If you’ve got an ESP32 lying around and don’t know what to do with it, you could always consider getting into game development.

 

3D Printing A Water Jet Drive

April 30, 2019 by 16 Comments

[Ivan Miranda] is always experimenting with 3D printing, and recently has been taking his work on the water. His latest creation is a racing paddle boat, but its performance left [Ivan] with a need for speed. Cue the development of the 3D printed water jet engine (YouTube link, embedded below).

The basic principle of operation is simple. Water is sucked through an inlet, where it is accelerated by a turbine driven by a brushless motor. This turbine, in combination with stator fins, forces the water through the outlet, propelling the boat forwards in the process.

The first prototype is printed in PLA. Tolerances are good, thanks largely to [Ivan]’s experience and well-calibrated printers. After assembly, the engine is fired up, to great results. After sourcing a series of larger tubs in which to test the device, the engine is finally run up to full throttle and appears more than capable of shifting a serious amount of water.

We’d love to see a proper instrumented thrust test, particularly one that compares the device to other water jet drives on the market. Brushless motors make a great drive solution for RC boats, so we’re sure [Ivan] will be tearing up the lake real soon. Video after the break.

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Hacking A Cheap EBay Frequency Counter

April 30, 2019 by 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 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 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 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 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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