Monoprice Mini Delta Review

For the last year or so, Monoprice has been teasing their follow-up to the fantastic $200 MP Select Mini. This is the $150 mini delta printer. We got a look at it last January at CES, it was on display at the Bay Area Maker Faire last May. Now there’s one on the Hackaday review desk.

Over the last few years, 3D printing has settled down into what most of us expected way back in 2010. No, not everyone wants, or arguably needs, a 3D printer on their desks. This is a far cry from the hype of a few years ago, leaving us with what we have today. 3D printers are just tools, much like a drill press or a laser cutter.

With that said, there still are some fantastic advances in 3D printing coming down from on high. Prusa will be shipping the 4-color multi-extruder add-on for the i3 Mk 2 shortly, and somehow or another we have infinite build volume printers. Still, there’s space to democratize 3D printing, and an opportunity for someone to release a very cheap, very good printer.

Monoprice was kind enough to send me a review unit of the MP Mini Delta before it officially hit their website. This is one of the first off the production line, alongside the few hundred pre ordered on an Indiegogo campaign earlier this year.  Does this printer live up to expectations? It sure does, and that’s not just because it’s a $150 printer.

This would be an excellent printer at three times the price, and evidence enough that 3D printing is changing from a weird hobbyist thing to a proper tool.

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Living on Mars: the Stuff You Never Thought About

In The Martian we saw what kind of hacking was needed to stay alive for a relatively short while on Mars, but what if you were trying to live there permanently? Mars’ hostile environment would affect your house, your transportation, even how you communicate. So here’s a fun thought experiment about how you’d live on Mars as part of a larger community.

Not Your Normal House

Mars One living units under regolith
Mars One living units under regolith, Source video

Radiation on Mars comes from solar particle events (SPE) and galactic cosmic radiation (GCR). Mars One, the organization planning one-way trips to Mars talks about covering their habitats in several meters of regolith, a fancy word for the miscellaneous rocky material covering the bedrock. Five meters provides the same protection as the Earth’s atmosphere — around 1,000 g/cm2 of shielding. A paper from the NASA Langley Research Center says that the largest reduction comes from the top 15 to 20 cm of regolith. And so our Mars house will have an underlying structure but the radiation protection will come from somewhere between 20 cm to a few meters of regolith. Effectively, people will be living underground.

On Earth, producing water and air for your house is not something you think of doing, let alone disposing of exhaled CO2. But Mars houses will need systems for this and more.

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Product Development and Avoiding Stock Problems

You’ve spent months developing your product, your Kickstarter just finished successfully, and now you’re ready to order all the parts. Unfortunately, your main component, an ATmega328P, is out of stock everywhere with a manufacturer lead time of 16 weeks. Now what?

When manufacturing things in large volumes, acquiring enough stock at the right time can be tricky. There can be seasonal shortages with companies trying to get products manufactured and available for Christmas. There can be natural disasters like floods of hard drive factories, or politically-related availability problems like tantalum for capacitors, or maybe new markets open up that increase demand or a new product sucks up all the available supply. The result is all the same; you have a harder time getting what you need. Fortunately, there are some ways to avoid this problem, or at least mitigate it.

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Hands On With The SHACamp 2017 Badge

The badge has become one of the defining features of a modern hacker camp, a wearable electronic device that serves as both event computer and platform for some mild software and hardware hacking. Some events have had astoundingly sophisticated badges while others are more simple affairs, and the phenomenon has even spawned an ecosystem of unofficial badges which have nothing to do with the event in question.

The SHACamp 2017 badge is the latest to come the way of a Hackaday writer, and certainly contains enough to be taken as representative of the state of hacker camp badges in 2017. It doesn’t have a star turn like CCCCamp 2015’s software defined radio, instead it’s an extremely handy little computer in its own right.

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Books You Should Read: IGNITION!

Isaac Asimov described the business of rocket fuel research as “playing footsie with liquids from Hell.” If that piques your interest even a little, even if you do nothing else today, read the first few pages of IGNITION! which is available online for free. I bet you won’t want to stop reading.

IGNITION! An Informal History of Liquid Rocket Propellants is about how modern liquid rocket fuel came to be. Written by John D. Clark and published in 1972, the title might at first glance make the book sound terribly dry — it’s not. Liquid rocket fuel made modern rocketry possible. But most of us have no involvement with it at all besides an awareness that it exists, and that makes it easy to take for granted.

Most of us lack any understanding of the fact that its development was the result of a whole lot of hard scientific work, and that work required brilliance (and bravery) and had many frustrating dead ends. It was also an amazingly dangerous business to be in. Isaac Asimov put it this way in the introduction:

“[A]nyone working with rocket fuels is outstandingly mad. I don’t mean garden-variety crazy or a merely raving lunatic. I mean a record-shattering exponent of far-out insanity.

There are, after all, some chemicals that explode shatteringly, some that flame ravenously, some that corrode hellishly, some that poison sneakily, and some that stink stenchily. As far as I know, though, only liquid rocket fuels have all these delightful properties combined into one delectable whole.”

At the time that the book was written and published, most of the work on liquid rocket fuels had been done in the 40’s, 50’s, and first half of the 60’s. There was plenty written about rocketry, but very little about the propellants themselves, and nothing at all written about why these specific substances and not something else were being used. John Clark — having run a laboratory doing propellant research for seventeen years — had a unique perspective of the whole business and took the time to write IGNITION! An Informal History of Liquid Rocket Propellants.

Liquid rocket propellant was in two parts: a fuel and an oxidizer. The combination is hypergolic; that is, the two spontaneously ignite and burn upon contact with each other. As an example of the kinds of details that mattered (i.e. all of them), the combustion process had to be rapid and complete. If the two liquids flow into the combustion chamber and ignite immediately, that’s good. If they form a small puddle and then ignite, that’s bad. There are myriad other considerations as well; the fuel must burn at a manageable temperature (so as not to destroy the motor), the energy density of the fuel must be high enough to be a practical fuel in the first place, and so on.

The actual process of discovering exactly what materials to use and how precisely to make them work in a rocket motor was the very essence of the phrase “the devil is in the details.” For every potential solution, there was a mountain of dead-end possibilities that tantalizingly, infuriatingly, almost worked.

The first reliable, workable propellant combination was Aniline and Red Fuming Nitric Acid (RFNA). “It had the one – but magnificent – virtue that it worked,” writes Clark. “Otherwise it was an abomination.” Aniline was difficult to procure, ferociously poisonous and rapidly absorbed through skin, and froze at an inconvenient -6.2 Celsius which limited it to warm weather only. RFNA was fantastically corrosive, and this alone went on to cause no end of problems. It couldn’t be left sitting in a rocket tank waiting to be used for too long, because after a while you wouldn’t have a tank left. It needed to be periodically vented while in storage. Pouring it gave off dense clouds of remarkably toxic gas. This propellant would go on to cause incredibly costly and dangerous problems, but it worked. Still, no one wanted to put up with any of it one moment longer than they absolutely had to. As a result, that combination was not much more than a first step in the whole process; there was plenty of work left to do.

By the mid-sixties, liquid rocket propellant was a solved problem and the propellant community had pretty much worked themselves out of a job. Happily, a result of that work was this book; it captures history and detail that otherwise would simply have disappeared.

Clark has a gift for writing, and the book is easy to read and full of amusing (and eye-widening) anecdotes. Clark doesn’t skimp on the scientific background, but always in an accessible way. It’s interesting, it’s relevant, it’s relatable, and there is plenty to learn about how hard scientific and engineering development actually gets done. Download the PDF onto your favorite device. You’ll find it well worth the handful of evenings it takes to read through it.

Failing Infrastructure and the Lessons It Teaches

Infrastructure seems so permanent and mundane that most of us never give it a second thought. Maintenance doesn’t make for a flashy news story, but you will frequently find a nagging story on the inside pages of the news cycle discussing the slowly degrading, crumbling infrastructure in the United States.

If not given proper attention, it’s easy for these structures to fall into a state of disrepair until one suddenly, and often catastrophically, fails. We’ve already looked at a precarious dam situation currently playing out in California, and although engineers have that situation under control for now, other times we haven’t been so lucky. Today we’ll delve into a couple of notable catastrophic failures and how they might be avoided in future designs.

Gaining Weight While Delaying Repairs

Most of us take infrastructure for granted every day. Power lines, roads, pipelines, and everything else have a sense of permanence and banality that can’t be easily shaken. Sadly, this reality shattered for most people in Minneapolis, Minnesota in August 2007.

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Earth Ground And The Grid

The electrical grid transmits power over wires to our houses, and our Bryan Cockfield has covered it very well in his Electrical Grid Demystified series, but what part does the earth ground play? It’s commonly known to be used for safety, but did you know that in some cases it’s also used for power transmission?

Typical House Grounding System

Grounding system normal case
Grounding system normal case

A pretty typical diagram for the grounding system for a house is shown here, along with a few of the current carrying conductors commonly called live and neutral. On the far left is the transformer outside the house and on the far right is an appliance that’s plugged in. In between them is a breaker panel and a wall socket of the style found in North America. The green dashed line shows the normal path for current to flow.

Notice the grounding electrodes for making an electrical connection with the earth ground. To use the US National Electrical Code (NEC) as an example, article 250.52 lists eight types of grounding electrodes. One very good type is an electrode encased in concrete since concrete continues to draw moisture from the ground and makes good physical contact due to its weight. Another is a grounding rod or pipe at least eight feet long and inserted deep enough into the ground. By deep enough, we mean to include factors such as the fact that the frost line doesn’t count as a good ground since it has a high resistance. You have to be careful of using metal water pipes that seemingly go into the ground, as sections of these are often replaced with non-metallic pipes during regular maintenance.

Notice also in the diagram that there are places where the various metal cases are connected to the grounding system. This is called bonding.

Now, how does all this system grounding help us? Let’s start with handling a fault.

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