Macintosh Hard Drive Repair

October 13, 2015 by 57 Comments

The Macintosh II was a popular computer in the era before Apple dominated the coffee shop user market, but for those of us still using our Mac II’s you may find that your SCSI hard drive isn’t performing the way that it should. Since this computer is somewhat of a relic and information on them is scarce, [TheKhakinator] posted his own hard drive repair procedure for these classic computers.

The root of the problem is that the Quantum SCSI hard drives that came with these computers use a rubber-style bump stop for the head, which becomes “gloopy” after some time. These computers are in the range of 28 years old, so “some time” is relative. The fix involves removing the magnets in the hard drive, which in [TheKhakinator]’s case was difficult because of an uncooperative screw, and removing the rubber bump stops. In this video, they were replaced with PVC, but [TheKhakinator] is open to suggestions if anyone knows of a better material choice.

This video is very informative and, if you’ve never seen the inside of a hard drive, is a pretty good instructional video about the internals. If you own one of these machines and are having the same problems, hopefully you can get your System 6 computer up and running now! Once you do, be sure to head over to the retro page and let us know how you did!

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Citizen Scientist: Forrest Mims

October 13, 2015 by 140 Comments

Before the modern notion of the citizen scientist lies the earlier ideal of the independent scientist. Scientists outside of the academic community but engaging with it. These days citizen scientists are often seen as valuable assistants in the scientific process, helping collect and process data in a quantity which would be otherwise intractable.

In the past however, independent scientists had a far more central role. Galileo, Kepler, Darwin and Hooke were all self funded at various points in their careers. More recently independent scientist Peter Mitchell won the Nobel prize for Chemistry in 1978 for his foundational research into cell biochemistry and the development of the chemiosmotic hypothesis.

Sadly, peer-reviewed scientific contributions by scientists un-sponsored by a research organization are now few and far between. In this short series we hope to highlight the efforts of these lone researchers with particular reference to the tools they’ve had to hack together on a budget in their scientific quests (if you know an independent researcher you think we should feature, please comment below!).

In Hacker circles Forrest Mims is perhaps best known for his series of electronics books and the unforgeable Atari Punk Console. But it’s his ability to engage with the scientific community as an independent researcher through a series of well thought out scientific articles that interests us here. Contributions made all the more significant by his lack of formal scientific training.

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Fail Of The Week: Marginally Documented Pad Shorts To Maskless PCB

October 13, 2015 by 33 Comments

[Erich Styger] was bit by a nasty gotcha when soldering a QFN surface mount chip. The problem rears its ugly head when combining a chip possessing a padless conductor and a PCB without a solder mask. As you can see in the image above, there is a conductor exiting the side of the plastic QFN, but there is no pad associated with it. For this reason, you won’t see the conductor documented in the datasheet as a pin. It is documented in the mechanical drawing of the package, without any explicit reference to its existence. This is the Jason Bourne of package quirks.

The PCB layout just happens to have a trace exiting right under this conductor. The two aren’t touching, but without solder mask, a bit of melted metal was able to mind the gap and connect the two conductors. [Eric] notes that although the non-pad isn’t documented, it’s easy to prove that it is connected to ground and was effectively pulling down the signal on that trace.

In a recent article on Hackaday I talked about “dangling pointers” and the challenge when interrupts expose the bug. [Erich’s] covered a ton of posts about embedded software. I was doing some poking around and was delighted to find that he covered the same concept and a solution for it using a program called cppcheck.

Tiny PIC Clock Is Not A Tiny Bomb

October 13, 2015 by 100 Comments

It’s been a few weeks since the incident where Ahmed Mohamed, a student, had one of his inventions mistaken for a bomb by his school and the police, despite the device clearly being a clock. We asked for submissions of all of your clock builds to show our support for Ahmed, and the latest one is the tiniest yet but still has all of the features of a full-sized clock (none of which is explosions).

[Markus]’s tiny clock uses a PIC24 which is a small yet powerful chip. The timekeeping is done on an RTCC peripheral, and the clock’s seven segment displays are temporarily lit when the user presses a button. Since the LEDs aren’t on all the time, and the PIC only consumes a few microamps on standby, the clock can go for years on a single charge of the small lithium-ion battery in the back. There’s also a phototransistor which dims the display in the dark, and a white LED which could be used as a small flashlight in a pinch. If these features and the build technique look familiar it’s because of [Markus’] tiny MSP430 clock which he was showing around last year.

Both of his tiny clocks are quite impressive for their size, features, and power consumption. Some of the other clocks we’ve featured recently include robot clocks, clocks for social good, and clocks that are not just clocks (but still won’t explode). We’re suckers for a good clock project here, so keep sending them in!

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DARE To Fly: Live Coverage Of A 50KM Rocket Launch

October 12, 2015 by 4 Comments

We wrote about the Delft Aerospace Rocket Engineering (DARE) project recently: a group of students at Delft Technical University who are trying to launch a rocket to 50kM, breaking the European amateur rocketry record. Now, the group is close to their latest launch attempt, which is scheduled to take place from their launch base in Spain between the 14th and the 20th of October.

Launch preparations are underway, with the team working through a 10,000 point pre-launch checklist. Last year, their launch failed because of a leaking valve, but the amateur engineers have just successfully completed a pressure test using inert gas, so they are confident that this problem won’t happen again. They are offering a live video feed of the launch (embedded below), and will be regularly updating their twitter feed as they prepare. We wish them the best of luck.

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Internet-Connected Box Displays Emotion, Basement Dwellers Still Unaffected

October 12, 2015 by 15 Comments

For one reason or another, Twitter has become the modern zeitgeist, chronicling the latest fashions, news, gossip, and irrelevant content that sends us spiraling towards an inevitable existential ennui. This is a Twitter mood light. It tells you what everyone else on the planet is feeling. You, of course, feel nothing. Because of the ennui.

[Connor] decided it would be a good idea to audit the world’s collective mood using experimental social analytics. He’s doing that by watching millions of tweets a day and checking them against hundreds of keywords for several emotions. These emotions are graphed in real time, placed on a server, correlated and corroborated, and downloaded by a moodLight. Inside the moodLight, the emotions are translated into colors, and displayed with the help of a few RGB LEDs.

The moodLight is currently a Kickstarter campaign, with a $30 pledge getting you an assembled board with an ATMega328, an ESP8266, a few RGB LEDs, and a laser cut enclosure. After it’s assembled, the moodLight connects automagically to the analytics server for a real-time display of the emotional state of the Twitterverse. The display is updated every second, making the backend of this build just slightly more impressive than Kickstarter itself. It’s great work from [Connor], and an interesting experiment in analyzing the state of the Internet.

Passive, But Not Innocuous

October 12, 2015 by 19 Comments

Maxim Integrated recently posted a series of application notes chronicling how there’s more going on than you’d think in even the simplest “passive” components. Nothing’s safe: capacitors, resistors, and even printed circuit boards can all behave in non-ideal ways, and that can bite you in the reflow-oven if you’re not aware of them.

You might already know that capacitors have an equivalent series resistance that limits how fast they can discharge, and an equivalent inductance that models departures from ideal behavior at higher frequencies. But did you know that ceramic capacitors can also act like voltage sources, acting piezoelectrically under physical stress?

For resistors, you’ll also have to reckon with temperature dependence as well as the same range of piezoelectric and inductance characteristics that capacitors display. Worse, resistors can display variable resistance under higher voltages, and actually produce a small amount of random noise: Johnson Noise that depends on the value of the resistance.

Finally, the third article in the series tackles the PCB, summarizing a lot of potential manufacturing defects to look out for, as well as covering the parasitic capacitance, leakage currents, and frequency dependence that the actual fiberglass layers themselves can introduce into your circuit.

If you’re having a feeling of déjà-vu, the same series of articles ran in 2013 in Electronic Design but they’re good enough that we hope you won’t mind the redundant repetition all over again. And if you’re already quibbling with exactly what they mean by “passive”, we feel your pain: they’re really talking about parasitic effects, but we’ll let that slide too. We’re in a giving mood today.

[via Dangerous Prototypes]