Thermistors And 3D Printing

December 15, 2017 by 24 Comments

I always find it interesting that 3D printers — at least the kind most of us have — are mostly open-loop devices. You tell the head to move four millimeters in the X direction and you assume that the stepper motors will make it so. Because of the mechanics, you can calculate that four millimeters is so many steps and direct the motor to take them. If something prevents that amount of travel you get a failed print. But there is one part of the printer that is part of a closed loop. It is very tiny, very important, but you don’t hear a whole lot about it. The thermistor.

The hot end and the heated bed will both have a temperature sensor that the firmware uses to keep temperatures at least in the ballpark. Depending on the controller it might just do on-and-off “bang-bang” control or it might do something as sophisticated as PID control. But either way, you set the desired temperature and the controller uses feedback from the thermistor to try to keep it there.

If you print with high-temperature materials you might have a thermocouple in your hot end, but most machines use a thermistor. These are usually good to about 300 °C. What got me thinking about this was the installation of an E3D V6 clone hot end into my oldest printer which had a five-year-old hot end in it. I had accumulated a variety of clone parts and had no idea what kind of thermistor was in the heat block I was using.

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Mount Sopris

Design A Microcontroller With Security In Mind

December 15, 2017 by 22 Comments

There are many parts to building a secure networked device, and the entire industry is still learning how to do it right. Resources are especially constrained for low-cost microcontroller devices. Would it be easier to build more secure devices if microcontrollers had security hardware built-in? That is the investigation of Project Sopris by Microsoft Research.

The researchers customized the MediaTek MT7687, a chip roughly comparable to the hacker darling ESP32. The most significant addition was a security subsystem. It performs tasks notoriously difficult to do correctly in software, such as random number generation and security key storage. It forms the core of what they called the “hardware-based secure root of trust.”

Doing these tasks in a security-specific module solves many problems. If a key is not stored in memory, a memory dump can’t compromise what isn’t there. Performing encryption/decryption in task-specific hardware makes it more difficult to execute successful side-channel attacks against them. Keeping things small keeps the cost down and also eases verifying correctness of the code.

But the security module can also be viewed from a less-favorable perspective. Its description resembles a scaled-down version of the Trusted Platform Module. As a self-contained module running its own code, it resembles the Intel Management Engine, which is currently under close scrutiny.

Will we welcome Project Sopris as a time-saving toolkit for building secure networked devices? Or will we become suspicious of hidden vulnerabilities? The researchers could open-source their work to ease these concerns, but value of their work will ultimately depend on the fast-moving field of networked device security.

Do you know of other efforts to add hardware-assisted security to microcontrollers? Comment below or let us know via the tip line!

[via Wired]

Image of Mount Sopris, namesake of the project, by [Hogs555] (CC-BY 4.0)

 

Hardware Heroes: Isambard Kingdom Brunel

December 15, 2017 by 45 Comments

There are some notable figures in history that you know of for just one single thing. They may have achieved much in their lifetimes or they may have only been famous for Andy Warhol’s fifteen minutes, but through the lens of time we only know them for that single achievement. Then on the other hand there are those historic figures for whom there is such a choice of their achievements that have stood the test of time, that it is difficult to characterize them by a single one.

[Isambard Kingdom Brunel], in front of the launching chains for the Great Eastern. [Public domain]
Isambard Kingdom Brunel, in front of the launching chains for the Great Eastern. [Public domain]
Such is the case of Isambard Kingdom Brunel, the subject of today’s Hardware Heroes piece. Do we remember him for his involvement in the first successful tunnel to pass beneath a river, as a builder of some of the most impressive bridges on the 19th century, the innovator in all aspects of rail engineering, the man behind the first screw-driven ocean-going iron ship, or do we remember him as all of those and more?

It is possible that if you are not British, or in particular you are not from the West of England, this is the first you’ve heard of Brunel. In which case he is best described as a towering figure of many aspects of engineering over the middle years of the 19th century. His influence extended from civil engineering through the then-emerging rail industry, to shipbuilding and more, and his legacy lives on today in that many of his works are still with us.

Engineering: The Family Trade

Brunel’s father, Marc Brunel, was an engineer and refugee from the French Revolution who found success in providing the British Navy with a mass-production system for wooden pulley blocks as used in the rigging of sailing ships. He enters this story for his grand project, the world’s first tunnel to be dug under a navigable river, beneath London’s River Thames from Rotherhithe to Wapping, and for his patented tunneling shield which made it possible to be dug.

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Modernizing Puerto Rico’s Grid

December 15, 2017 by 44 Comments

After two massive hurricanes impacted Puerto Rico three months ago, the island was left with extensive damage to its electrical infrastructure. Part of the problem was that the infrastructure was woefully inadequate to withstand a hurricane impact at all. It is possible to harden buildings and infrastructure against extreme weather, and a new plan to restore Puerto Rico’s power grid will address many of these changes that, frankly, should have been made long ago.

Among the upgrades to the power distribution system are improvements to SCADA systems. SCADA allows for remote monitoring and control of substations, switchgear, and other equipment which minimizes the need for crews to investigate problems and improves reliability. SCADA can also be used for automation on a large scale, in addition to the installation of other autonomous equipment meant to isolate faults and restore power quickly. The grid will get physical upgrades as well, including equipment like poles, wire, and substations that are designed and installed to a more rigorous standard in order to make them more wind- and flood-tolerant. Additional infrastructure will be placed underground as well, and a more aggressive tree trimming program will be put in place.

The plan also calls for some 21st-century improvements as well, including the implementation of “micro grids”. These micro grids reduce the power system’s reliance on centralized power plants by placing small generation facilities (generators, rooftop solar, etc) in critical areas, like at hospitals. Micro grids can also be used in remote areas to improve reliability where it is often impractical or uneconomical to service.

While hurricanes are inevitable in certain parts of the world, the damage that they cause is often exacerbated by poor design and bad planning. Especially in the mysterious world of power generation and distribution, a robust infrastructure is extremely important for the health, safety, and well-being of the people who rely on it. Hopefully these steps will improve Puerto Rico’s situation, especially since this won’t be the last time a major storm impacts the island.

Retractable Console Allows Wheelchair User To Get Up Close And Personal

December 15, 2017 by 5 Comments

[Rhonda] has multiple sclerosis (MS), a disease that limits her ability to walk and use her arms. She and the other residents of The Boston Home, an extended care facility for people with MS and other neuromuscular diseases, rely on their wheelchairs for mobility. [Rhonda]’s chair comes with a control console that swings out of the way to allow her to come up close to tables and counters, but she has problems applying enough force to manually position it.

Sadly, [Rhonda]’s insurance doesn’t cover a commercial solution to her problem. But The Boston Home has a fully equipped shop to extend and enhance residents’ wheelchairs, and they got together with students from MIT’s Principles and Practices of Assistive Technology (PPAT) course to hack a solution that’s not only useful for [Rhonda] but should be generally applicable to other chairs. The students analyzed the problem, measured the forces needed and the clearances required, and built a prototype pantograph mount for the control console. They’ve made the device simple to replicate and kept the BOM as inexpensive as possible since patients are often out-of-pocket for enhancements like these. The video below shows a little about the problem and the solution.

Wheelchair hacks are pretty common, like the 2015 Hackaday Prize-winning Eyedrivomatic. We’ve also covered totally open-source wheelchairs, both manual and electric.

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Dumb Coffee Grinder Gets Smarter With Time

December 14, 2017 by 10 Comments

[Forklift] has a Rancilio Rocky, a prosumer-level coffee grinder that’s been a popular mainstay for the last few decades. It’s a simple machine with a direct-drive motor. Rocky has one job, and it will do that job in one of 55 slightly different ways as long as someone is pushing the grind button. What Rocky doesn’t have is any kind of metering technology. There’s no way to govern the grind length, so repeatable results rely on visual estimates and/or an external clock. Well, there wasn’t until [Forklift] designed a programmable timer from the ground up.

The timer interface is simple—there’s a D-pad of buttons for navigation through the OLED screen, and one button to start the grind. The left and right buttons move through four programmable presets that get stored in the EEPROM of the timer’s bare ATMega328P brain. Grind duration can be adjusted with the up/down buttons.

We like that [Forklift] chose to power it by piggybacking on the 240VAC going to the grinder. The cord through the existing grommet and connects with spade terminals, so there are no permanent modifications to the grinder. Everything about this project is open source, including the files for the 7-segment font [Forklift] designed.

Tea aficionados may argue that creating their potion is the more time sensitive endeavor. We’ve got you covered there. Only question is, one button or two?