Why You Shouldn’t Quite Forget The Moving Coil Multimeter

November 8, 2017 by 80 Comments
Did any of you have an AWS multimeter? Was it the best? Radio-electronics magazine, August 1981.
Did any of you have an AWS multimeter? Was it the best? Radio-Electronics magazine, August 1981.

If you were to ask a random Hackaday reader what their most fundamental piece of electronic test equipment was, it’s likely that they would respond with “multimeter”. If you asked them to produce it, out would come a familiar item, a handheld brick with a 7-segment LCD at the top, a chunky rotary selector switch, and a pair of test probes. They can be had with varying quality and features for anything from a few dollars to a few hundred dollars, though they will nearly all share the same basic set of capabilities. Voltage in both AC and DC, DC current, resistance from ohms to mega ohms, and maybe a continuity tester. More expensive models have more features, may be autoranging, and will certainly have better electrical safety than the cheaper ones, but by and large they are a pretty standard item.

If Hackaday had been around forty years ago and you’d asked the same question, you’d have had a completely different set of multimeters pulled out for your inspection. Probably still a handheld brick with the big selector switch, but instead of that LCD you’d have seen a large moving-coil meter with a selection of scales for the different ranges. It would have done substantially the same job as the digital equivalent from today, but in those intervening decades it’s a piece of equipment that’s largely gone. So today I’m going to investigate moving coil multimeters, why you see them a lot less these days than you used to, and why you should still consider having one in your armoury. Continue reading “Why You Shouldn’t Quite Forget The Moving Coil Multimeter” →

Colette Biometric Security Purse Screams When Stolen

November 8, 2017 by 18 Comments

A team of college hackers was disappointed with the selection of secure purses available. Nearly every purse on the market is attractive, secure, or neither so they are designing their own security purse with some style. Instead of just brass or leather clasps keeping unwanted hands out, they are upgrading to automation and steel.

Everything starts with a fingerprint reader connected to an Arduino. Once an acceptable finger is recognized, a motor opens a coffin lock, also known as a butt-joint fastener, which can be completely hidden inside the purse and provides a lot of holding force. That is enough to keep quick fingers from reaching into an unattended purse.

In the case of a mugging, a sound grenade will trigger which should convince most thieves to quickly abandon it. Then, the internal GPS tells the owner where the purse can be found.

We can’t imagine a real-life purse thief prepared to tackle this kind of hardware. Hackaday loves knowing the ins and out of security from purses to cars and of course IoT.

Laser Levitation With Scrap Parts

November 8, 2017 by 37 Comments

After a year away from YouTube, the ever-energetic [Styropyro] has returned with whiteboard in hand to remind us just how little we actually know about lasers. In the last month he’s really hit the ground running with plenty of new content, but one video of his particularly stands out: a practical demonstration of laser levitation. Even better, unlike most of his projects, it looks like we can replicate this one without killing ourselves or burning our house down!

For those unaware, laser levitation is probably as close as we’ll get to Star Trek-style tractor beams in our lifetimes. In fact, the NASA Innovative Advanced Concepts program has been examining using the technology for capturing small particles in space, since it would allow sample collection without the risk of physical contamination. While the demonstration [Styropyro] performs lacks the “tractor” part of the equation (in other word’s, there’s no way to move the particle along the length of the beam) it does make us hopeful that this type of technology is not completely outside the reach of our home labs.

The trick seems to be with the focus of the laser beam itself. Your average laser pointer just doesn’t have the appropriate beam for this kind of work, but with a diode pulled from a DVD burner and a driver circuit made from parts out of the junk bin, the effect can be demonstrated very easily as long as you can keep the air in the room extremely still. Of course, what you’re trying to pick up is also very important, [Styropyro] has found that synthetic diamond powder works exceptionally well for this experiment. At about $1.60 a gram, it won’t break the bank either.

So how does it work? With a few trips to the aforementioned white board, Professor Pyro explains that the effect we’re seeing is actually electromagnetic. If the particle you want to levitate is small enough it will become polarized by the light, which is in itself an electromagnetic wave. Once you’ve got your mind wrapped around that, it logically follows that the levitating particle will experience the Lorentz force. Long story short, the particle is suspended in the air for the same reason that a projectile is ejected from a rail gun: if you’ve got enough power and the mass of the object is low enough, there will be an observable force.

We’ve been covering the work of [Styropyro] for years now, and are glad to see him back on YouTube creating new content and terrifying a new generation of viewers. Between this and the return of [Jeri Ellsworth], it’s like we’re experiencing a YouTube hacker Renaissance.

Continue reading “Laser Levitation With Scrap Parts” →

Romanian Cobra clone

Romania’s 1980s Illicit DIY Computer Movement

November 7, 2017 by 52 Comments

In Western countries in the early 1980s, there was plenty of choice if you wanted an affordable computer: Apple, Atari, TRS-80, Commodore and Sinclair to name a few. But in communist-ruled Romania, mainly you’d find clones of the British Sinclair ZX Spectrum, an 8-bit computer built around the Zilog Z80A, using a CRT TV as display and a BASIC interpreter as UI. The Cobra was one such Romanian Sinclair clone. However, most people couldn’t afford even that, which lead to hackers building their own versions of the Cobra.

Making these clones was highly illegal. But that didn’t stop students at the Politehnica University of Bucharest. They made them for themselves, family and friends, and even sold them at well under market price. To keep people from building radio transmitters, the Communist government kept electronics prices high. So instead, parts smuggled from factories could be paid for with a pack of cigarettes.

Look inside an old Apple II and you’ll see a sea of chips accomplishing what can be done with only a few today. The Cobra clones looked much the same, but with even more chips. Using whatever they could get their hands on, the students would make 30 chips do the job of an elusive $10 chip. No two computers were necessarily alike. Even the keyboards were hacked together, sometimes using keys designed for mainframe computers but with faults from the molding process. These were cleaned up and new letters put on. The results are awesome hacks which fit right in here on Hackaday.

Sadly though, it often takes harsh necessity to make a culture where these inspiring hacks thrive in the mainstream. Another such country which we’ve reported on this happening in is Cuba, which found the necessity first when the U.S. left Cuba in the 60s and again when the Soviet Union collapsed in the 90s, reducing the availability of many factory produced items needed for daily life, and creating a DIY society.

Bionic Eye Trial Approved

November 7, 2017 by 27 Comments

Pixium Vision, a French company, has received the approval to begin in-human trials of a miniature wireless sub-retinal implant. Named PRIMA, the device may help those with advanced dry age-related macular degeneration get improvements in their eyesight. The company is in talks to also conduct trials in the United States.

The PRIMA implant is a photovoltaic chip about 2mm square and only 30 microns thick. That’s tiny, but the device has 378 electrodes. The patient uses a device that looks like a conventional pair of glasses but contains an integrated camera that sends data wirelessly to a small pocket-sized image processing computer. This computer then commands the glasses to send data to the implant via invisible infrared light. The chip converts the light to electrical impulses and conducts them to the optic nerve. You can see a video about how the system works below.

Continue reading “Bionic Eye Trial Approved” →

Heat-Set Insert Jig Grants Threads To 3D Prints

November 7, 2017 by 28 Comments

FDM 3D prints might be coming home this holiday as seasonal ornaments, but with a few tweaks, they may even stand up to the tests of the real world as functional prototypes. Heat-Set inserts are one such tweak that we can drop into a print, and [Kurt] spares no expense at laying down a guide to get us comfortable with these parts. Here, he’s created a drill press adapter and modified his soldering iron to form an insert jig to start melting these parts into his next project.

Heat-set inserts grant us proper screw threads in any thermoplastic. Simply heat them up, stake them into your part, let cool, and: voila–a screw thread that’s firmly embedded into our part. We can load these inserts with clumsy hand tools, but why fumble and bumble with a hot soldering iron when we can adapt our drill press to do most of the tricky fixturing for us? That’s exactly what [Kurt] did here. With a 3D-printed adaptor, he’s letting his drill press (turned off!) hold the soldering iron so that he can use the lever to slowly stake the part into the 3D print. Finally, for no additional charge, [Kurt] turned down his soldering tip to mate cleanly into the insert for a cleaner removal.

We’ve seen adapters like this one before, but it’s never too often to get a reminder of the structural bonus that these parts can add to our 3D prints.

Remote Controlled Jeep Destroyed For Your Amusement

November 7, 2017 by 17 Comments

Something you learn when you spend a good portion of your day trolling the Internet for creative and unique projects is that “Why?” is one question you should always be careful about asking. Just try to accept that, for this particular person, at this particular time, the project they poured heart and soul into just made sense. Trust us, it’s a lot easier that way.

This mantra is perhaps best exemplified (at least for today), by the incredible amount of work [Stephen Robinson] did to convert a real Jeep Cherokee into a remote control toy. But the crazy part it isn’t so much that he managed to convert a real Jeep to RC, it’s that the first thing he did with it was take it into a field and destroy it.

The stunt is part of a series of videos [Stephen] has on his YouTube channel called “How to learn anything”. His goal in this series is to learn two different skills from industry professionals and combine them in interesting and unconventional ways. The production quality on these videos is really top-notch, and definitely blew us away considering how few subscribers he currently has. If we had to guess, we’d say [Stephen] is about to get real big, real fast.

As it turns out, the process for turning a full size vehicle into a remote-controlled one isn’t actually that complex, relatively speaking. [Stephen] starts by removing the seat and replacing it with a metal frame that holds a motor salvaged from an electric wheelchair to turn the wheel, and a linear actuator to push the brake pedal. He lucked out a bit with the throttle, as this particular Jeep was old enough that there was still an easily accessible throttle cable they could yank with a standard hobby servo; rather than some electronic system they would have had to reverse engineer.

The rest of the hardware is pretty much your standard RC hobby gear, including a Spektrum DX6 transmitter and FPV equipment. Though due to continual problems with his FPV setup, [Stephen] eventually had to drive the Jeep up the ramp by line of sight, which took a few tries.

While this is still probably safer than riding around in a life-size quadcopter, we can’t say it’s the most sophisticated way a hacker has taken over a Jeep remotely.

Continue reading “Remote Controlled Jeep Destroyed For Your Amusement” →