Flash Memory: Caveat Emptor

May 13, 2018 by 29 Comments

We all love new tech. Some of us love getting the bleeding edge, barely-on-the-market devices and some enjoy getting tech thirty years after the fact to revel in nostalgia. The similarity is that we assume we know what we’re buying and only the latter category expects used parts. But, what if the prior category is getting used parts in a new case? The University of Alabama in Huntsville has a tool for protecting us from unscrupulous manufacturers installing old flash memory.

Flash memory usually lasts longer than the devices where it is installed, so there is a market for used chips which are still “good enough” to pass for new. Of course, this is highly unethical. You would not expect to find a used transmission in your brand new car so why should your brand new tablet contain someone’s discarded memory?

The principles of flash memory are well explained by comparing them to an ordinary transistor, of which we are happy to educate you. Wear-and-tear on flash memory starts right away and the erase time gets longer and longer. By measuring how long it takes to erase, it is possible to accurately determine the age of chip in question.

Pushing the limits of flash memory’s life-span can tell a lot about how to avoid operation disruption or you can build a flash drive from parts you know are used.

3D Printing Air Quality Study

May 13, 2018 by 18 Comments

You’ll often hear about some study in the media and then — on examination — find it doesn’t really apply to your situation. Sure, substance X causes cancer in rats, but they ate 8 pounds of it a day for a decade. That’s why we were glad to see [Chuck] post a series of videos about 3D printing air quality based on his practical experience. You can see the summary video, below.

[Chuck] is quick to point out that he isn’t a doctor or even a chemist. He also admits the $100 meter from IGERESS he is using isn’t necessarily high-quality test gear. Still, the data is a good guideline and he did get repeatable results.

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Build Your Own Avionics Suite, If You Dare

May 13, 2018 by 25 Comments

If you’re really interested in aircraft and flying, there are many ways to explore that interest. There are models of a wide range of sizes and complexities that are powered and remote-controlled, and even some small lightweight aircraft that can get you airborne yourself for a minimum of expense. If you’re lucky enough to have your own proper airplane, though, and you’re really into open source projects, you can also replace your airplane’s avionics kit with your own open source one.

Avionics are the electronics that control and monitor the aircraft, and they’re a significant part of the aircraft’s ability to fly properly. This avionics package from [j-omega] (who can also be found on hackaday.io) will fit onto a small aircraft engine and monitor things like oil temperature, RPM, coolant temperature, and a wide array of other features of the engine. It’s based on an ATmega microcontroller, and has open-source schematics for the entire project and instructions for building it yourself. Right now it doesn’t seem like the firmware is available on the GitHub page yet, but will hopefully be posted soon for anyone who’s interested in an open-source avionics package like this.

The project page does mention that this is experimental as well, so it might not be advised to use in your own personal aircraft without some proper testing first. That being said, if you’ve heard that warning and have decided just to stay on the ground, it’s possible to have a great experience without getting in a real airplane at all.

Sign Of The Smith Chart Times

May 13, 2018 by 5 Comments

The Smith chart is a staple for analyzing complex impedance. [W2AEW] notes that a lot of inexpensive test gear like the MFJ-259B gives you complex readings, but fails to provide the sign of the imaginary part of the complex number. That makes it difficult to plot the results on a Smith chart or carry out other analysis. As you might expect, though, he has a solution for you that you can see in the video, below.

A common method is to increase the frequency slightly. In a simple case, you’d expect the imaginary part — the reactance — to go down for a capacitive impedance and up for an inductive one. Unfortunately, this doesn’t apply in many common cases, including when you are measuring through a transmission line which is probably what most people are doing with this type of test gear.

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Battery-Powered Watering Timer Converted To Solar On The Cheap

May 12, 2018 by 13 Comments

Watering the garden or the lawn is one of those springtime chores that is way more appealing early in the season than later. As the growing season grinds along, a chore that seemed life-giving and satisfying becomes, well, just another chore, and plants often suffer for it.

Automating the watering task can be as simple as buying a little electronic timer valve that turns on the flow at the appointed times. [A1ronzo] converted his water hose timer to solar power. Most such timers are very similar, with a solenoid-operated pilot valve in line with the water supply and an electronic timer of some sort. The whole thing is quite capable of running on a pair of AA batteries, but rather than wasting money on new batteries several times a season, he slipped a LiPo pack and a charge controller into the battery case slot and connected a small solar panel to the top of the controller.

The LiPo is a nominal 3.7-volt pack, so he did a little testing to make sure the timer would be OK with the higher voltage. The solar panel sits on top of the case, and the whole thing should last for years. And bonus points for never having to replace a timer that you put away at the end of the season with batteries still in it, only to have them leak. Ask us how we know.

Like the best of hacks, this one is quick, easy and cheap — $15 in parts, aside from the timer. There are more complicated irrigation solutions, of course, one of which even won the Hackaday Prize once upon a time. But this one has us ordering parts to build our own right now.

HFT On HF, You Can’t Beat It For Latency

May 12, 2018 by 14 Comments

If you are a radio enthusiast of A Certain Age, you may well go misty-eyed from time to time with memories of shortwave listening in decades past. Countries across the world operated their own propaganda radio stations, and you could hear Radio Moscow’s take on world events, the BBC World Service responding, and Radio Tirana proudly announcing that every Albanian village now had a telephone. Many of those shortwave broadcast stations are now long gone, but if you imagine the HF spectrum is dead, think again. An unexpected find in an industrial park near Chicago led to an interesting look at the world of high-frequency trading, or HFT, and how they have moved to using shortwave links when everyone else has abandoned them, because of the unparalleled low latency they offer when communicating across the world.

Our intrepid tower-hunter is [KE9YQ], who was out cycling and noticed a particularly unusual structure adorned with a set of HF beams. These are the large directional antennas of the type you might otherwise expect to see on the roof of an embassy or in the backyard of a well-heeled radio amateur, and were particularly unusual in this otherwise unexciting part of America. There followed an interesting process of tracking down the site’s owners via the FCC permits for its operation, leading to the deduction of its purpose. With other antenna-hunters on the lookout for corresponding sites elsewhere in the world, it seems that this unusual global network hiding in plain sight could soon be revealed.

Unsurprisingly we’ve not covered many shortwave HFT stories. There are however other higher-latency ways to cross the world on HF.

Via SWLing Post, and thanks [W6MOQ] for the tip.

A Two-Range OLED Capacitance Meter

May 12, 2018 by 14 Comments

If you are just starting out in electronics, you need tools. But it is hard to build all your tools. Even though we see a lot of soldering station builds, you really ought to have a soldering iron to build the station. It is hard to troubleshoot a multimeter you just built if you don’t have a multimeter. However, a capacitance meter is a handy piece of gear, relatively simple to build, and you should be able to get it working without an existing capacitance meter. [gavinlyonsrepo] presents a simple design using an Arduino, an OLED display, and a few components.

The principle of operation is classic. On one range, the Arduino charges the capacitor through one resistor and discharges it through another while timing the operation. The amount of time taken corresponds to the capacitance.

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