Statistics And Hacking: An Introduction To Hypothesis Testing

December 1, 2017 by Sean Boyce 20 Comments

In the early 20^th century, Guinness breweries in Dublin had a policy of hiring the best graduates from Oxford and Cambridge to improve their industrial processes. At the time, it was considered a trade secret that they were using statistical methods to improve their process and product.

One problem they were having was that the z-test (a commonly used test at the time) required large sample sizes, and sufficient data was often unavailable. By studying the properties of small sample sizes, William Sealy Gosset developed a statistical test that required fewer samples to produce a reasonable result. As the story goes though, chemists at Guinness were forbidden from publishing their findings.

So he did what many of us would do: realizing the finding was important to disseminate, he adopted a pseudonym (‘Student’) and published it. Even though we now know who developed the test, it’s still called “Student’s t-test” and it remains widely used across scientific disciplines.

It’s a cute little story of math, anonymity, and beer… but what can we do with it? As it turns out, it’s something we could probably all be using more often, given the number of Internet-connected sensors we’ve been playing with. Today our goal is to cover hypothesis testing and the basic z-test, as these are fundamental to understanding how the t-test works. We’ll return to the t-test soon — with real data. Continue reading “Statistics And Hacking: An Introduction To Hypothesis Testing” →

Making An Arduino Shield PCB With Fritzing

November 26, 2017 by Donald Papp 15 Comments

[Allan Schwartz] decided to document his experience using Fritzing to design, fabricate, and test a custom Arduino shield PCB, and his step-by-step documentation makes the workflow very clear. Anyone who is curious or has been looking for an opportunity to get started will find [Allan]’s process useful to follow. The PCB in question has two shift registers, eight LEDs, eight buttons, and fits onto an Arduino; it’s just complex enough to demonstrate useful design features and methods while remaining accessible.

[Allan] starts with a basic breadboard design, draws a schematic, prototypes the circuit, then designs the PCB and orders it online, followed by assembly and testing. [Allan] had previously taught himself to use Eagle and etched his own PCBs via the toner transfer method, but decided to use Fritzing instead this time around and found it helpful and easy to use.

About a year ago we saw Fritzing put through its paces for PCB design, and at the time found that it didn’t impress much from an engineering perspective. Regardless, as a hobbyist [Allan] found real value in using Fritzing for his project from beginning to end; he documented both the process and his observations in order to help others, and that’s wonderful.

Dumb Box? Make It Really Smart!

November 23, 2017 by Donald Papp 6 Comments

[Stephen Harrison]’s Really Smart Box is a great concept, it’s simultaneously a simple idea while at the same time being super clever. The Really Smart Box isn’t really a box; it’s a drop-in platform that can be made any size, intended to turn any dumb storage box into one that helps manage and track levels and usage of any sort of stock or consumable.

It does this by measuring the weight of the stuff piled on top of it, while also monitoring temperature and humidity. The platform communicates this information wirelessly to a back end, allowing decisions to be made about stock levels, usage, and monitoring of storage conditions. It’s clearly best applied to consumables or other stock that comes and goes. The Really Smart Box platform is battery-powered, but spends most of its time asleep to maximize battery life. The prototype uses the SigFox IoT framework for the wireless data, which we have seen before in a wireless swimming pool monitor.

This is still just a prototype and there are bugs to iron out, but it works and [Stephen] intends to set-and-forget the prototype into the Cambridge Makespace with the task of storing and monitoring 3D printer filament. A brief demo video is embedded below.

Continue reading “Dumb Box? Make It Really Smart!” →

Tips For Basic Machining On A Drill Press

November 19, 2017 by Tom Nardi 77 Comments

It’s safe to say most Hackaday readers would love to have a mill at home, or a nice lathe, but such equipment isn’t always practical for the hobbyist. The expense and amount of room they take up is a hard sell unless you’re building things on them regularly, so we’re often forced to improvise. In his latest video, [Eric Strebel] gives some practical advice on using a standard drill press to perform tasks you would normally need a mill or lathe for; and while his tips probably won’t come as a surprise to the old-hands out there, they might just help some of the newer players get the most out of what they have access to.

[Eric] explains the concept of the cross slide vice, which is the piece of equipment that makes machining on a drill press possible. Essentially it’s a standard vice, but with screws that allow you to move the clamped piece in the X and Y dimensions under the drill which can already move in the Z dimension. For those counting along at home, that puts us up to the full three dimensions; in other words, you can not only make cuts of varying depths, but move the cut along the surface of the work piece in any direction.

You can even turn down a (small) piece of round stock by placing it in the chuck of the drill press, and putting a good chisel in the cross slide vice. The chisel can then be moved up against the spinning piece to make your cuts. We don’t suggest doing anything too heavy, but if you need to turn down something soft like a piece of plastic or wood to a certain diameter, it can do in a pinch.

[Eric Strebel] is quickly becoming a favorite around these parts. His well-produced videos show viewers the practical side of product design and in-house manufacturing. We recently covered his video on doing small-scale production, and there’s plenty more invaluable info to be had browsing back through his older videos.

The quest to do machining without actually having a machine shop is certainly not new to Hackaday. There have been many different approaches to solving the issue, but picking up a decent drill press and cross slide is a first step down the rabbit hole for most people.

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Visual 3D Print Finishing Guide

November 15, 2017 by Tom Nardi 52 Comments

With 3D printers now dropping to record low prices, more and more people are getting on the additive manufacturing bandwagon. As a long time believer in consumer-level desktop 3D printing, this is a very exciting time for me; the creativity coming out of places like Thingiverse or the 3D printing communities on Reddit is absolutely incredible. But the realist in me knows that despite what slick promotional material from the manufacturers may lead you to believe, these aren’t Star Trek-level replicators. What comes out of these machines is often riddled with imperfections (from small to soul crushing), and can require considerable cleanup work before they start to look like finished pieces.

If all you hope to get out of your 3D printer are some decent toy boats and some low-poly Pokemon, then have no fear. Even the most finicky of cheap printers can pump those out all day. But if you’re looking to build display pieces, cosplay props, or even prototypes that are worth showing to investors, you’ve got some work cut out for you.

With time, patience, and a few commercial products, you can accomplish the ultimate goal: turning a 3D printed object into something that doesn’t look like it was 3D printed. For the purposes of this demonstration I’ll be creating a replica of the mobile emitter used by the “Emergency Medical Hologram” in Star Trek: Voyager. I can neither confirm nor deny I selected this example due to the fact that I’m currently re-watching Voyager on Netflix. Let’s make it look good.

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Less Than Production, More Than One-Offs

November 14, 2017 by Brian McEvoy 18 Comments

We build things we think are cool. Sometimes, other people agree with us and they want a copy of what we’ve built. If you’re lucky enough to have an enviable product but you’re not ready for full-scale manufacturing, you may be looking at a low-volume production run. [Eric Strebel] walks us through one such instance where he makes some custom color swatches for a show. Video after the break.

[Eric Strebel] is an industrial designer so he plays to his strengths by designing the swatch shape, jig, tool, and hangers. He hires out the painting, laser cutting, and CNC machining. This may seem like a simple statement but some of us have a hard time paying other people for things we’re capable of learning. In some cases, we just have to pay the professionals to do it correctly and keep our focus.

The mentality of small runs in this video is perfect for people who sell on Tindie or want to make more than a handful of consistently nice parts. Our own [Lewin Day] recently talked about his experience with a run of 200 mixers called gMix.

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Lathe Turns The Corner, Makes A Cube

November 13, 2017 by Kristina Panos 27 Comments

[Tim] was tired of using his lathe to turn round things. He decided to make a gaming die—something that’s iconically square—out of cylindrical scrap. As it turns out, this is possible to do on a lathe with a three jaw chuck. [Tim] discovered that the bevel on the jaws will hold a cylindrical puck of scrap sideways while he squares off the round sides into faces.

Turning a cube on a lathe looks pretty fiddly, so we applaud [Tim]’s lovely handiwork even more. As you’ll see in the video down below, things were going gangbusters until he went to make the last facing cut. Maybe the tool wasn’t lined up just so, or something was off in the chucking, but the first pass made a bit of a gouge in the stock. Looks like it was easy enough to fix, though. After four 90° turns and facing cuts, he had a nice looking rough cube to work with.

This is a regulation-sized die, so the next step was to trim it down to 16mm³. Then it was time to sand, polish, and add the dots. To lay them out, [Tim] sprayed the cube with layout fluid and scribed unique line patterns on each face. Then he drilled the indentations and filled them in with aluminium black.

Most of the dice we see are electronic, like this extremely random pair and these PIC-driven LED dice. We’d like to see [Tim] make a second D6 so he has a pair. And then make a D20. Please?

Continue reading “Lathe Turns The Corner, Makes A Cube” →