The Science Behind Lithium Cell Characteristics and Safety

To describe the constraints on developing consumer battery technology as ‘challenging’ is an enormous understatement. The ideal rechargeable battery has conflicting properties – it has to store large amounts of energy, safely release or absorb large amounts of it on demand, and must be unable to release that energy upon failure. It also has to be cheap, nontoxic, lightweight, and scalable.

As a result, consumer battery technologies represent a compromise between competing goals. Modern rechargeable lithium batteries are no exception, although overall they are a marvel of engineering. Mobile technology would not be anywhere near as good as it is today without them. We’re not saying you cannot have cellphones based on lead-acid batteries (in fact the Motorola 2600 ‘Bag Phone’ was one), but you had better have large pockets. Also a stout belt or… some type of harness? It turns out lead is heavy.

The Motorola 2600 ‘bag phone’, with a lead-acid battery. Image CC-BY-SA 3.0 source: Trent021

Rechargeable lithium cells have evolved tremendously over the years since their commercial release in 1991. Early on in their development, small grains plated with lithium metal were used, which had several disadvantages including loss of cell capacity over time, internal short circuits, and fairly high levels of heat generation. To solve these problems, there were two main approaches: the use of polymer electrolytes, and the use of graphite electrodes to contain the lithium ions rather than use lithium metal. From these two approaches, lithium-ion (Li-ion) and lithium-polymer (Li-Po) cells were developed (Vincent, 2009, p. 163). Since then, many different chemistries have been developed.

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A Noob’s Guide to McMaster-Carr

For the penny-pinching basement hacker, McMaster-Carr seems like a weird go-to resource for hardware. For one, they’re primarily a B2B company; and, for two, their prices aren’t cheap. Yet their name is ubiquitous among the hacker community. Why? Despite the price, something makes them too useful to ignore by everyday DIY enthusiasts. Those of us who’ve already been enlightened by the McMaster-Carr can design wonders with a vocabulary of parts just one day away at the click of a button.

Today, this article is for those of us who have yet to receive that enlightenment. When used wisely, this source of mechanical everything brings us a world of fast parts at our fingertips. When used poorly, we find nothing but overpriced stock components in oversized shipping boxes.

Since we, the McMaster-Carr sages, are forever doomed to stuff our desk drawers with those characteristic yellow baggies till the end of time, we thought we’d give an intro to the noobs that are just beginning to flex their muscles with this almighty resource. Grab another cup of coffee as we take you on a tour of the good and good-grievances of McMaster-Carr.

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Video Streaming Like Your Raspberry Pi Depended On It

The Raspberry Pi is an incredibly versatile computing platform, particularly when it comes to embedded applications. They’re used in all kinds of security and monitoring projects to take still shots over time, or record video footage for later review. It’s remarkably easy to do, and there’s a wide variety of tools available to get the job done.

However, if you need live video with as little latency as possible, things get more difficult. I was building a remotely controlled vehicle that uses the cellular data network for communication. Minimizing latency was key to making the vehicle easy to drive. Thus I set sail for the nearest search engine and begun researching my problem.

My first approach to the challenge was the venerable VLC Media Player. Initial experiments were sadly fraught with issues. Getting the software to recognize the webcam plugged into my Pi Zero took forever, and when I did get eventually get the stream up and running, it was far too laggy to be useful. Streaming over WiFi and waving my hands in front of the camera showed I had a delay of at least two or three seconds. While I could have possibly optimized it further, I decided to move on and try to find something a little more lightweight.

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How To Do PCB Art In Eagle

Last month I had the pleasure of creating a new piece of hardware for Tindie. [Jasmine], the queen bee of Tindie, and I designed, developed, and kitted three hundred Tindie badges in ten days leading up to DEF CON. The badges were a complete success, they introduced soldering to a lot of people, and were loved by all.

This badge was such a rousing success, it’s now official Tindie swag. We’ll be handing out a few of these blinky badges at upcoming events. But as of right now we’ve already handed out our entire stock, that means we need to build more. The second run meant ordering a thousand PCBs.

We could just do another run, and order a few more PCBs from the Gerbers I’ve already designed. I’m not really happy with the first version of this badge, though, and this is an opportunity to improve my design. This also gives me an opportunity to demonstrate my workflow for creating artistic boards in Eagle.

Effectively, what I’ll be demonstrating here is the creation of the Benchoff Nickel. A few months ago, [Andrew Sowa] took a portrait of yours truly, changed the colors to what is available on a normal OSHPark PCB, and turned that into different layers in KiCad. There are a few differences here. Firstly, I’ll be using a blue solder mask, although the same technique can be applied to green, red, yellow, white, or black soldermask. Secondly, this is Eagle, and I’m going to do the majority of the work with a BMP import. This is the fast and easy way to do things; if you want a KiCad tutorial, check out [Andrew]’s work, or my overly-involved multiple silkscreen process for KiCad. I don’t recommend this overly-involved process if you can help it. It took 20 hours to do the art for my previous project in KiCad, and I estimate it would have taken two in Eagle.

With that said, here’s the easy, cheap, and fast way of doing artistic boards in Eagle.

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Modular Storage with Peanut Butter and Lasers

I have storage on the mind, and it comes from two facts in my life:

First, I have tons of stuff in my workshop, far too much for the amount of space I have. A lot of this material is much easier to use if it’s well-organized. Think electronics, robotics, building sets. Modular parts that need to go together a certain way for them to be useful. It is imperative, therefore, that I come up with some sort of organization system to keep the chaos in check.

Second, my favorite tool is the laser cutter, born from my love for building vector designs. I can do art on the computer and have it manufactured in front of my eyes, and share my designs with someone else who can remix it into something even cooler.

So with those two facts in mind, I set about creating a modular storage system in Inkscape and cutting out the design from pine boards using a laser cutter. Let us go on a journey through my thought process:

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Lasering Axonometric Fonts

I am something of an Inkscape fan. If you’re not familiar with the application, it’s like an Open Source version of Adobe Illustrator. Back when I was a production artist I’d been an Illustrator master ninja but it’s been four years and my skills are rusty. Plus, Inkscape is just enough different in terms of menus and capabilities that I had a hard time adapting.

So I created some wooden lettering with the help of Inkscape and a laser cutter, and I’m going to show you how I did it. If you’re interested in following along with this project, you can find it on

While playing around with Inkscape, I noticed you can create a variety of grids, including axonometric grids. This term refers to the horizon lines in an orthographic projection. In other words, it helps make things look 3D by providing perspective lines.

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Testing Distance Sensors

I’m working on a project involving the need to precisely move a tool based on the measured distance to an object. Okay, yeah, it’s a CNC mill. Anyway, I’d heard of time of fight sensors and decided to get one to test out, but also to be thorough I wanted to include other distance sensors as well: a Sharp digital distance sensor as well as a more sophisticated proximity/light sensor. I plugged them all into a breadboard and ran them through their paces, using a frame built from aluminum beams as a way of holding the target materials at a specific height.

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