Author: Al Williams

4506 Articles

Fake Omron Relays Are Worth What You Pay For Them

May 11, 2018 by 40 Comments

We love taking a look at fake components and [BigClive] has put together something really special in this category. When he saw he could buy suspiciously cheap Omron relays on eBay, he knew something must be fishy so he put in an order.

Some of the fakes he received are even marked Omrch instead of Omron, and your ear can detect the counterfeits by the varying sounds they make during operation. But of course [Clive’s] investigation goes much deeper than that. He started driving the relays to their rated voltages and taking temperatures with a FLIR camera.

The results were not surprising. At lower voltages the relays seemed to do okay, but closer to the maximums it’s obvious the components in the fakes are not rated for enough power to work. You can even see some charring of a resistor and its plastic holder from having too much power for the component’s rating. [Clive] actually replaced the errant resistor with a higher value resistor that reduces the current consumption and power dissipated.

He was also suspicious of the metal content of the contacts. You may think that doesn’t matter, but actually, the composition of relay contacts is critical to making reliable relay circuits. Depending on how much current flows and if the switching is dry (that is, made without current flowing) or not dictates use of different material.

The conclusion was that these relays might work for light duty projects, but for commercial projects or operating near the edge of the ratings, you want to give these a pass. If you do need a lot of low-power relays on the cheap — to compute a square root, or to build the whole computer — [Clive’s] process of testing and characterizing these fakes may come in handy for you.

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Diablo Drive Appears To Be Cursed

May 10, 2018 by 11 Comments

[CuriousMarc] didn’t think it would be a big deal when a former Xerox employee sent him an Alto Diablo drive for service. Turns out the drive was cursed — it would destroy everything it touched including a set of heads and an alignment cartridge. [Marc] and a partner spent two months trying to get the drive operable and the video of their process is pretty interesting.

We were interested in the troubleshooting, but we were really envious of their lab, full of HP workstations, an IBM mainframe, and even a Selectric. We kept having to rewind the video because we had tuned out while we were staring at some of the equipment in the background.

The guys got a lot of practice aligning the heads on the drive. Because the crashed head was bent, it actually dug into the alignment cartridge so on subsequent attempts they had to manually load the disk past the damage. They learned to leave the disk a little out of alignment because tightening the assembly will move it a little bit. If you were already aligned, the heads would be off after you did the tightening.

They used a custom FPGA-based tester that [Carl] developed after reverse engineering the disk format. It is amazing to watch the big drive in action and realize that a standard cartridge for this machine was 2.5 megabytes. There was another controller and disk system called the Trident that would get you a whopping 80 megabytes, but we don’t think this is one of those.

Did they succeed in exorcising whatever demons lived in the drive? Watch the video and find out. Even if you never have to fix a Diablo drive yourself, you’ll be entertained. Especially when they work out how to do a current adjustment on the drive by simulating the circuit in Spice.

We’ve seen a lot about the Alto which is surprising considering how few of them were built. We’ve seen a restoration and even an odd use for a light bulb related to the Alto’s CRT.

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Vector Network Analyzer Uses SoC FPGA

May 9, 2018 by 15 Comments

If you are working with AC circuits a vector network analyzer (VNA) is quite handy. As an entry to the InnovateFPGA competition for students, [Evgenii Vostrikov], [Danila Nikiforovskii], and [Daniil Smirnov] created a VNA using a DE10-Nano, high-speed analog to digital and digital to analog converters, and a circulator. Most of the details are in the video below, and on the project’s GitHub page.

The DE10-Nano has a dual-core ARM processor and an Altera FPGA in one package. That allows you to use the CPUs where that makes sense and still leverage the FPGA where you need high performance.

The circulator uses an op-amp to allow the test signal to route to the device under test, while steering any reflected signal back to the device for measurement. The design also uses a lock-in amplifier, something we’ve talked about a few times recently. This allows less expensive converters to generate magnitude and phase information.

Judging by the fan in the video, we suspect the setup gets a little toasty. The GitHub page has a lot of Russian on it, so we aren’t sure how much we could puzzle out since our Russian skills were mostly from watching the Adventures of Moose and Squirrel.

If you are interested in a VNA, they aren’t as expensive as they used to be. Particularly, if you roll your own and already have some things in your junk box.

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Breadboarding: Git For A/B Testing Actual Bread

May 9, 2018 by 17 Comments

We will be the first to admit, we like to use Git for a lot of things that are probably off the beaten path. But now thanks to [hendricius] you can find out how to make your own bread on GitHub. Let’s get one thing straight. This isn’t the breadmaker fad from a while back, although we are surprised we don’t see more hacked together breadmakers with Internet connectivity. This is old-fashioned bread baking with a bowl, some ingredients, and an oven or another heat source.

You might think this is just using Git as a repository for recipes, but it is more than that. According to [hendricius]:

Learn how to master the art of baking the programmer way. If you love programming, you will also enjoy breaking some bread. A/B test, iterate and ultimately become a self-taught baker. This repository is dedicated to becoming your bread manifesto with useful tricks and hacks. Furthermore, the goal is to illustrate how easy making bread is and that you can get started today without expensive tools.

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Harmony Hub Hacked And Patched

May 7, 2018 by 15 Comments

When we say “hack” here we most often mean either modifying something to do something different or building something out of parts. But as we build more Internet-connected things, it is worthwhile to think about the other kind of hack where people gain unauthorized access to a system. For example, you wouldn’t think a remote control would be a big deal for hackers. But the Logitech Harmony Hub connects to the Internet and runs Linux. What’s more is it can control smart devices like door locks and thermostats, so hacking it could cause problems. FireEye’s Mandian Red Team set out to hack the Harmony and found it had a lot of huge security problems.

The remote didn’t check Logitech’s SSL certificate for validity. It didn’t have a secure update process. There were developer tools (an SSH server) left inactive in the production firmware and — surprisingly — the root password was blank! The team shared their findings with Logitech before publishing the report and the latest patch from the company fixes these problems. But it is instructive to think about how your Raspberry Pi project would fare under the same scrutiny.

In fact, that’s the most interesting part of the story is the blow-by-blow description of the attack. We won’t spoil the details, but the approach was to feed the device a fake update package that turned on a dormant ssh server. Although they started by trying to solder wires to a serial port, that wasn’t productive and the final attack didn’t require any of that.

We’ve looked at some ways to harden Linux systems like the Raspberry Pi before, but honestly, it is an ongoing battle. We’ve seen plenty of devices with cybersecurity holes in them — some not found by good guy hackers first.

3D Printed Bicycle Tire Not Full Of Hot Air

May 7, 2018 by 30 Comments

To show off its new TPU filament called PRO FLEX, BigRep GmbH posted a video showing a 3D printed bike tire that uses a flexible plastic structure instead of air. The video shows them driving the bike around Berlin.

According to the company, the filament will allow the creation of a large number of industrial objects not readily built with other types of plastic. Their release claims the material has high temperature resistance, low temperature impact resistance, and is highly durable. Applications include gear knobs, door handles, skateboard wheels, and other flexible parts that need to be durable.

The material has a Shore 98 A rating. By way of comparison, a shoe heel is typically about 80 on the same scale and an automobile tire is usually around 70 or so. The hard rubber wheels you find on shopping carts are about the same hardness rating as PRO FLEX.

Obviously, a bicycle tire is going to take a big printer. BigRep is the company that makes the BigRep One which has a large build volume. Even with a wide diameter tip, though, be prepared to wait. One of their case studies is entitled, “Large Architectural Model 3D Printed in Only 11 Days.” Large, in this case, is a 1:50 scale model of a villa. Not tiny, but still.

We’ve looked at other large printers in the past including 3DMonstr, and the Gigimaker. Of course, the latest trend is printers with a practically infinite build volume.

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Algorithms For Visual Learners

May 6, 2018 by 10 Comments

Computer programming is a lot like chess. It is fairly simple to teach people the moves. But knowing how the pieces move isn’t the reason you can win. You have to understand how the pieces work together. It is easy to learn the mechanics of a for loop or a Java interface. But what makes programs work are algorithms. There are many books and classes dedicated to algorithms, but if you are a visual learner, you might be interested in a site that shows visualizations of algorithms called VisuAlgo.

The site is from [Dr. Steven Halim] and is meant for students at the National University of Singapore, but it is available “free of charge for Computer Science community on earth.” We suspect if any astronauts or cosmonauts wanted to use it in space, they’d be OK with that, too.

The animations and commentary take you through algorithms ranging from the common — sorting and linked lists — to the obscure — Steiner and Fenwick trees. Each animation frame has some commentary, so it isn’t just pretty pictures. The site is available in many languages, too.

Many of the animations allow you to set up problems and execute them using a C-like pseudo language. When it executes, you can watch the execution pointer and a box comments on the current operation. For example, in the linked list unit, you can create a random doubly linked list and then search it for a particular value. Not only can you see the code, but the graphical representation of the list will update as the code runs.

The site allows you to register for free to get additional features, but we didn’t and it was still a great read about many different data structures. Also, a few of the commentary slides require you to show you are actually a computer science professor — we assume there’s some copyright issue involved because it is only a few.

This site is a great example of how many free educational resources are out there on the web. It isn’t just computer science either. MITx — or more generally, edX — has some great hardware classes and many other topics