classic hacks

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Twisted String Actuators

January 17, 2015 by 39 Comments

[Travis] tells us about a neat actuator concept that’s as old as dirt. It’s capable of lifting 7kg when powered by a pager motor, and the only real component is a piece of string.

The concept behind the twisted string actuator, as it’s known to academia, is as simple as putting a motor on one end of a piece of string, tying the other end off to a load, and putting a few twists in the string. It’s an amazingly simple concept that has been known and used for thousands of years: ballistas and bow-string fire starters use the same theory.

Although the concept of a twisted string actuator is intuitively known by anyone over the age of six, there aren’t many studies and even fewer projects that use this extremely high gear ratio, low power, and very cheap form of linear motion. A study from 2012 (PDF) put some empirical data behind this simple device. The takeaway from this study is that tension on the string doesn’t matter, and more strands or larger diameter strands means the actuator shrinks with a fewer number of turns. Fewer strands and smaller diameter strands take more turns to shrink to the same length.

As for useful applications of these twisted string actuators, there are a few projects that have used these systems in anthropomorphic hands and elbows. No surprise there, really; strings don’t take up much space, and they work just like muscles and tendons do in the human body.

Thanks [ar0cketman] for the link.

Best Of The Dinosaur Den 2014

January 7, 2015 by 3 Comments

If you haven’t been watching The Dinosaur Den, shame on you. This joint enterprise between [Fran Blanche] and our very own [Bil Herd] premiered in July and it is, simply put, the duck’s guts. In spite of being introduced to each other just a few months before the first episode, they banter like old friends. When they’re not riffing off each other, they’re giving a show and tell of all kinds of vintage technology. Most importantly, they’re always wearing really cool t-shirts.

Hot on the heels of their excellent holiday special comes this Best of the Dinosaur Den 2014 highlight reel. Some of our favorite bits are from said holiday special, because they spent the whole hour talking about their best-loved toys from holidays past, most of which started them on their paths to greatness. Come for the t-shirts, stay for the Zaxxon tabletop arcade and the toy that probably inspired LittleBits. Check out the best-of after the break, and then cook a Hot Pocket or something and watch them all. You’re pretty much guaranteed to learn something cool and/or useful.

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A Scanning Electron Microscope For The Living Room

January 6, 2015 by 23 Comments

There are hackers who have soldering setups on the dining room table, and then there are hackers who have scanning electron microscopes in their living room. [Macona] is part of the latter group, with a Hitachi S-450 SEM he’s repaired and modified himself. [Macona] has documented the whole thing on Hackaday.io. The Hitachi came to him and a friend as a derelict. First it was broken, then stored for 10 years. It turned out the problem was a high voltage cable cut and spliced with electrical tape. The tape eventually broke down and shorted out the 500V supply. Thankfully the rectifier diodes were the only parts that needed to be replaced.

analog1The SEM sprang to life and gave [Macona] and a friend their first images. However, SEMs are finicky beasts. Eventually the filament burned out and needed to be replaced. New filaments are $500 US for a box of 10, which is more than [Macona] wanted to spend. It turns out filaments can be built at home. A bit of .089mm tungsten wire and a spot welder were all it took to fix the issue. Next to go bad was the scan amplifier. While SEMs use many exotic parts, the Hitachi used relatively common Sanyo STK070 audio amplifiers for the purpose – an easy fix!

One thing that makes this SEM unique is the is Energy Dispersive X-Ray Spectroscopy (EDX) unit attached to it. The fragile liquid nitrogen cooled sensor was working, but the 1980’s era signal processing computer was a bit too old to bring up. A friend and fellow SEM hobbiest gave [Macona] a slightly newer Kevex Sigma Gold signal processor, which was nearly a plug and play upgrade for his machine. The new processor processor also gave him digital beam controls and a digital output which could be used to capture images with a PC.

Once all the connections were made, the EDX worked surprisingly well, even finding gold in a uranium ore sample placed in the microscope.

Now that old scanning electron microscopes being retired, it’s only a matter of time before more us get a chance to join the ranks of [Jeri Ellsworth], [Ben Krasnow] and [Macona] with our own personal SEMs!

Game Boy Cartridge Emulator Uses STM32

December 30, 2014 by 20 Comments

Game Boys may be old tech, but they still provide challenges to modern hackers. [Dhole] has come up with a cartridge emulator which uses an STMicroelectronics STM32F4 discovery board to do all the work. Until now, most flash cartridges used programmable logic devices, either CPLDs or FPGAs to handle the high-speed logic requirements. [Alex] proved that a microcontroller could emulate a cartridge by using an Arduino to display the “Nintendo” Game Boy boot logo. The Arduino wasn’t fast enough to actually handle high-speed accesses required for game play.

[Dhole] kicked the speed up by moving to the ARM Cortex-M4 based 168 MHz STM32F4. The F4’s  70 GPIO pins can run via internal peripherals at up to 100MHz, which is plenty to handle the 1MHz clock speed of the Game Boy’s bus. Logic levels are an issue, as the STM32 uses 3.3V logic while the Game Boy is a 5V device. Thankfully the STM32’s inputs are 5V tolerant, so things worked just fine.

Simple Game Boy cartridges like Tetris were able to directly map a ROM device into the Game Boys memory space. More complex titles used Memory Block Controller (MBC) chips to map sections of ROM and perform other duties. There were several MBC chips used for various titles, but [Dhole] can emulate MBC1, which is compatible with the largest code base.

One of the coolest tricks [Dhole] implemented was displaying a custom boot logo. The Game Boy used the “Nintendo” logo as a method of copyright protection. If a cartridge didn’t have the logo, the Game Boy wouldn’t run. The logo is actually read twice – once to check the copyright info, and once to display it on the screen. By telling the emulator to change the data available at those addresses after the first read, any graphic can be displayed.

If you’re wondering what a cartridge emulator would be useful for (other than pirating games), you should check out [Jeff Frohwein’s] Gameboy Dev page! [Jeff] has been involved in Game Boy development since the early days. There are literally decades of demos and homebrew games out there for the Game Boy and various derivatives. .

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Z80, CP/M, And FAT File Formats

December 30, 2014 by 18 Comments

[Gary Kildall] and CP/M are the great ‘also ran’ of the computing world; CP/M could run on thousands of different 1980s computers, and [Gary] saw a few million in revenue each year thanks to CP/M’s popularity. Microsoft, DOS, and circumstances have relegated [Kildall] and CP/M to a rather long footnote in the history of microcomputers, but that doesn’t mean CP/M is completely dead yet. [Marcelo] wrote a Z80 emulator running CP/M inside an Arduino Due, and he did it in such a way that it’s actually convenient and useful to use.

Instead of using CP/M disk images, [Marcelo]’s emulator emulates CP/M disk drives on top of a regular FAT file system. Drives are mapped to folders in the FAT file system, so a folder named ‘A’ will show up as the A: disk in CP/M. Drives up to P: are supported, the maximum number of drives available under CP/M. The BIOS resides in the root directory of the SD card, and so far Microsoft Basic, Turbo Pascal, UCD Micromumps, and Wordstar work just fine.

The Arduino project was built upon one of [Marcelo]’s earlier projects that put the CP/M emulator on Windows. The version for the Due works exactly how you think it would, with a serial connection and terminal emulator providing the IO, and the huge amount of processing power and RAM available on the Due doing all the heavy lifting.

Robotically-Tuned Tube Radio

December 27, 2014 by 8 Comments

Dubbed the “Robot Radio” by [Brek], this clinking-&-clunking project merges three generations of hackers’ favorite technologies: robots, vacuum tubes, and microcontrollers. After the human inputs the desired radio frequency the machine chisels its way through the spectrum, trying its best to stay on target.

This build began its life as a junky old tube radio that [Brek] pulled out of a shed. The case was restored and then the hacking began. Inserted between the human and the radio, a PIC 16F628A keeps watch in both directions. On one side, the radio’s tank circuit is monitored to see what frequency the radio is currently playing. On the other, the human’s input sets a desired frequency. If the two do not match, the PIC tells a stepper motor to begin cranking a pair of gears until they do.

Another interesting feature is that as the tubes and other electronics warm up and change their values, the matching circuit will keep them in line. [Brek] shows this in the video by deliberately sabotaging the gears and seeing the robot adjust them back where they belong.

As an afterthought, the Robot Radio was supplemented with a module that adds 100khz to the signal so that the information from a nearby airport can be received.

[Brek] styled the whole machine up with some copper framing and other bits, similar to his spectacular atomic clock build we featured last month.

See the video of the radio tuning after the break.

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NeXT Cubes And LCD Monitors

December 27, 2014 by 16 Comments

The NeXT slabs and cubes were interesting computers for their time, with new interesting applications that are commonplace today seen first in this block of black plastic. Web browsers, for example, were first seen on the NeXT.

Running one of these machines today isn’t exactly easy; there are odd video connectors but you can modify some of the parts and stick them in an LCD monitor. It’s a tradeoff between a big, classic, heavy but contemporary CRT and a modern, light, and efficient LCD, but it’s still a great way to get a cube or slab up and running if you don’t have the huge monitor handy.

The NeXT cube doesn’t have a single wire going between the computer and the monitor; that would be far too simple. Instead, a NeXT Sound Box sits between the two, providing the user a place to plug the monitor, keyboard, mouse, and audio connectors into. [Brian] took the board from this Sound Box and put it inside an old NEC LCD monitor he had sitting around. 12V and 5V rails were wired in, the video lines were wired in, and [Brian] created a new NeXT monitor.

There are two versions of the NeXT Sound Box – one for ADB peripherals (Apple IIgs and beige Macs), and another for non-ADB peripherals. [Brian] also put together a tutorial for using non-ADB peripherals with the much more common ADB Sound Board.