Retrotechtacular: The Last Main Line

If you were to nominate a technology from the 19th century that most defined it and which had the greatest effect in shaping it, you might well settle upon the railway. Over the century what had started as horse-drawn mining tramways evolved into a global network of high-speed transport that meant travel times to almost anywhere in the world on land shrank from months or weeks to days or hours.

For Brits, by the end of the century a comprehensive network connected almost all but the very smallest towns and villages. There had been many railway companies formed over the years to build railways of all sizes, but these had largely conglomerated into a series of competing companies with a regional focus. Each one had its own main line, all of which radiated out from London to the regions like the spokes of a wheel.

A Ruston steam navvy excavating near Wembley, London. S.W.A.Newton/Leicestershire County Council (Fair use)
A Ruston steam navvy excavating near Wembley, London. S.W.A.Newton/Leicestershire County Council (Fair use)

By the 1890s there was only one large and ambitious railway company left that had not built a London main line. The Great Central Railway’s heartlands lay in the North Midlands and the North of England, yet had never extended southwards. In the 1890s they launched their ambitious scheme to build  their London connection, an entirely new line from their existing Nottingham station to a new terminus at Marylebone, in London.

Since this was the last of the great British main lines, and built many decades after its rivals, it saw the benefit of the century’s technological advancement. Gone were the thousands of navvies (construction workers, from “Navigational”) digging and moving soil and rock by hand, and in their place the excavation was performed using the latest steam shovels. The latest standards were used in its design, too, with shallow curves and gradients, no level crossings, and a wider Continental loading gauge in anticipation of a future channel tunnel to France This was a high-speed railway built sixty years before modern high-speed trains, and nearly ninety years before the Channel Tunnel was opened.

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WTF Are Ground Loops?

These magical creatures crop up out of nowhere and fry your electronics or annoy your ear holes. Understanding them will doubtless save you money and hassle. The ground loop in a nutshell is what happens when two separate devices (A and B) are connected to ground separately, and then also connected to each other through some kind of communication cable with a ground, creating a loop. This provides two separate paths to ground (B can go through its own connection to ground or it can go through the ground of the cable to A and then to A’s ground), and means that current may start flowing in unanticipated ways. This is particularly noticeable in analog AV setups, where the result is audio hum or visible bars in a picture, but is also sometimes the cause of unexplained equipment failures. Continue reading “WTF Are Ground Loops?”

Don’t Fear The Filter: Lowpass Edition

There comes a time in every electronic designer’s life when, whether they know it or not, they need an analog filter in their design. If you’re coming from a digital background, where everything is nice and numeric, the harsh reality of continuous voltages can be a bit of a shock. But if you’re taking input from, or sending output to the big analog world out there, it pays to at least think about the frequency-domain properties of the signal, and maybe even do something about them.

Designing an analog filter to fit your needs can be a bit of a daunting task: there are many factors that you’re going to need to consider, and they all interact. It’s easy to get lost. We’re going to simplify this as much as possible by instead focusing on a few common applications and building up the simplest possible filters that work well for them.

Today, we’re going to consider the lowpass filter, and specifically a Sallen-Key filter with Butterworth characteristics and a second-order rolloff. Sound like word salad? We’ll fix that up right away, because this is probably the single most important filter to have in your analog toolbox for two very common use cases: pulse-width modulated (PWM) output and analog-to-digital conversion (ADC) input.

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Friday Hack Chat: Mechanical Manufacturing

Join [Sylvia Wu], a Senior Manufacturing Engineer at Fictiv, for this week’s Hack Chat. [Sylvia’s] work at Fictiv gives her a unique viewpoint for modern manufacturing. The company connects engineers with rapid manufacturing by taking in a design and routing it to a shop that has the tools and time to fabricate the part quickly. This means seeing the same silly mistakes over and over again, but also catching the coolest new tricks as they pass by. She also spends time tearing apart consumer products to see how they have been manufactured, adding to their arsenal of available processes, both time-tested and newfangled.

Anyone interested manufacturing needs to get in on this Hack Chat. Mark your calendar for this Friday, 3/10 at noon PST (20:00 UTC)

Here’s How To Take Part:

join-hack-chatOur Hack Chats are live community events on the Hackaday.io Hack Chat group messaging.

Log into Hackaday.io, visit that page, and look for the ‘Join this Project’ Button. Once you’re part of the project, the button will change to ‘Team Messaging’, which takes you directly to the Hack Chat.

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.

Upcoming Hack Chats

On Friday March 17th the Hack Chat features chip design for oscilloscopes with engineers from Keysight.

Saved By The Bel — Understanding Decibels

If you’ve hung around electronics for any length of time, you’ve surely heard of the decibel (often abbreviated dB). The decibel is a measure of a power ratio. Actually, the real measure is a bel, but you almost never see that in practice. If you are versed in metric, you won’t be surprised to learn a decibel is 1/10 of a bel. Sometimes in electronics, we deal with really large ratios, so the decibel is logarithmic to cope with this. Doubling the number of decibels doesn’t double the ratio, as you will soon see. It’s all about logarithms, and this ends up being extremely useful when measuring something like antenna or amplifier gain.

Besides antennas, decibels are often used to measure sound and light. The reason is that human ears and eyes have a logarithmic response to those quantities. Your ear, for example, has a huge dynamic range. That is to say, you can hear a whisper or a space shuttle launch. That ratio is about 1 trillion to 1, but that’s only 120 dB. This is also why potentiometers made for volume controls have a logarithmic taper. A linear pot would seem off because, for example, a tenth of a turn at one extreme will affect the apparent volume much more than a tenth of a turn at the other extreme. This holds true whether or not those knobs go up to eleven.

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Los Angeles Hackaday Unconference Happening On 3/18

Reserve your spot at the Los Angeles Hackaday Unconference on Saturday, March 18th. The Hackaday community is huge in LA and this event will fill up, so don’t delay.

The Unconference is a unique opportunity to decide the course of the day as it happens. Everyone who attends should be ready to stand and deliver at least eight minutes on a topic they find exciting right now. The energy this creates is the key to a level of involvement that can’t be matched at traditional conferences that have a divide between those presenting and those attending.

LA Joins Chicago and San Francisco

This announcement of the Los Angeles Hackaday Unconference joins two others happening the same day. Last week we announced San Francisco as a host location and the event is now full… but anyone in the area should still get their name on the waiting list. Four days ago we announced Chicago as the second location and that event will likely reach capacity today. [Shulie Tornel] and [Jasmine Brackett] are organizing things at the LA event which is being held at the Supplyframe Design Lab from 1 – 8 pm on 3/18.

Build Something that Matters

You can speak on any topic you want, but sometimes having a theme helps to get the ideas flowing. When considering your topic, keep Build Something that Matters in mind. Have you been looking into a technology, project, or idea that can make life a little (or a lot) better for the world? That would be an exquisite topic.

At the beginning of the day we’ll go around the room and get the talk title or subject from everyone there, then as a group we’ll hammer out a schedule for the day. As presentations progress, we encourage new impromptu talks to spring up, and can even split those off into a second talk space or discussion group. We’ll have food and drink on hand, as well as some interesting hardware to give out as door prizes.

The Hackaday Unconference is the ultimate idea and energy exchange in a crowd of your peers. You’ll have a hard time finding a cooler way to spend a Saturday this year. See you there!

Ask Hackaday: How Should Hackers Handle IP Agreements?

My buddy Harold recently landed a new job at a great technology company. It came at a perfect time for him, having just been laid off from the corporate behemoth where he’d toiled away as an anonymous cog for 19 years. But the day before he was to start, the new company’s HR folks sent him some last-minute documents to sign. One was a broad and vaguely worded non-compete agreement which essentially said he was barred from working in any related industry for a year after leaving the company.

Harold was tempted not to sign, but eventually relented because one needs to put food on the table. Thankfully he’s now thriving at the new company, but his experience got me thinking about all the complications hackers face with the day jobs that so many of us need to maintain. Non-competes and non-disclosures are bad enough, but there’s one agreement that can really foul things up for a hacker: the Intellectual Property Agreement.

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