The Fastest Rise Time In The West: Making A Truly Quick Pulse Edge

When we are taught about oscillators as newbie engineers, we are shown a variety of waveforms on an oscilloscope or in a textbook. This is a sine wave, they say, this is a sawtooth, this is a square wave, and so on. We’re taught to look at the lines on the screen as idealised, a square wave is truly square, and the transition from low to high voltage and back again is instantaneous.

In most cases this assumption is harmless. If we look into the subject a little deeper we learn that what seemed an instantaneous cliff-face is in fact a very steep slope, but when a circuit does its business in milliseconds there is usually no harm in ignoring a transition time measured in nanoseconds. The glue logic for your Arduino project can take its time.

Sometimes though, the rise time of a logic transition is important. The application that prompted this article was the measurement of oscilloscope bandwidth by looking at how quickly the ‘scope catches up with a pulse that exceeds its bandwidth, for example. When the instrument can happily measure the transition times of all your usual  pulse generators, something out of the ordinary is called for. So it’s worth taking a look at the rise times you’d expect from everyday circuitry, examining a few techniques for generating rise times that are much faster.
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What Lies Beneath: The First Transatlantic Communications Cables

For some reason, communications and power infrastructure fascinates me, especially the long-haul lines that move power and data over huge distances. There’s something about the scale of these projects that really gets to me, whether it’s a high-tension line marching across the countryside or a cell tower on some remote mountain peak. I recently wrote about infrastructure with a field guide that outlines some of the equipment you can spot on utility poles. But the poles and wires all have to end at the shore. Naturally we have to wonder about the history of the utilities you can’t see – the ones that run under the sea.

Hacking VM For Peak Performance

[Cyber Explorer] recently ditched his collection of physical computers acting as servers by virtualizing the lot of them. But with every change there’s a drawback. Although it wasn’t too hard for him to set up the virtual machines, he did end up spending quite a bit of time trying to improve the bandwidth. Luckily he posted an article chronicling all of the VM tweaks he used to improve the system.

The experience involves both a Windows 8 machine, as well as a some Linux boxes meaning there’s something here for everybody. At each step in the process he performs some throughput tests to see how the boxes are performing. Tweaks are numerous, but include trying out different Ethernet drivers, making sure all modules are up to date, squashing at least one bug, and giving jumbo-frames a try.

[Thanks Omri]

Exercise Bike Actuates Your Download Speeds; Messes With Music Playback

We’re not featuring this project because it involves the tiniest exercise bike in the world. It’s on the front page because the speed-control features which this dynamic duo added are hilarious. They call it the Webcycle and it’s actually two hacks in one.

Way back in 2009 [Matt Gray] and [Tom Scott] slapped an Arduino on the bike and used it to measure the revolutions of the cranks (how fast your feet are going in circles). This was hooked up to the laptop which is fastened to the handlebars. This way you can surf the Internet while you work out, but the bandwidth is directly affected by pedal speed. If you want to watch video you’re going to have to sweat…. a lot. Check it out in the clip after the break.

This March they pulled the Webcycle out of storage so that it may ride again. This time it’s connected to the sound system in their exercise room. A record player motor is the victim in this case. You guessed it — pedal speed dictates the rate of the turntable, modulating the pitch drastically. Make sure the boss isn’t around when you watch this clip because it will be hard not to guffaw.

These guys really have fun with this hacks. It was [Tom’s] birthday that prompted that hacktacular mini golf course.

Measuring Home Networks With BISMark

The Broadband Internet Service BenchMARK is an open source initiative to put tools in the hands of the common Internet user that will make measurement and analyzation of home network traffic easier. It targets LAN and WAN network utilization by measuring latency, packet loss, jitter, upstream throughput, and downstream throughput. Of course gathering data isn’t worth anything unless you have a way to present it, and to that end the Project BISMark team has been developing a web interface where you can view the usage of anyone who’s running the firmware.

The project builds on top of OpenWRT, which means that you should be able to run it on any router that’s OpenWRT compatible. This includes the ubiquitous WRT54G routers and many others. We remember when DD-WRT added bandwidth monitoring as part of the standard release, which really came in handy when the stories about ISP bandwidth capping started to hit. We’re glad to see even more functionality with this package as it can be hard to really understand what is going on in your network. After the break you’ll find a video detailing the features of BISMark.

Double The Hertz, Double The Pleasure

[tinhead] has opened up a Tekway DST1102B oscilloscope and doubled its bandwidth to 200MHz, sharing his work in the eevblog forum. This is great news to anyone who is looking for a faster sampling rate but can’t afford the high-end models. Mind you, for a lot of us even these Hanteks and Tekways are hard to afford but there are more appropriate options for the ramen-dependent hacker.

In the hacking guide [tinhead] includes comprehensive information on the different scopes he originally considered (a Rigol, Atten and UniTrend) before settling on the Tekway, as well as links to regional distributors for the hackable scope. Good quality benchtop units are invaluable for development and troubleshooting, and it pays off to understand their inner workings. It’s heartwarming to know that even the tools of hacking can be hacked.

Building A Bandwidth Meter

Here’s an analog bandwidth meter made to look like an old pressure gauge. It’s actually new, but the paper showing the graduated scale was stained in a bath of black tea, then dried in an oven to give it an aged appearance. We think it’s quite effective.

The dial itself is a volt meter driven by an Arduino in much the same way as the multimeter clock. Bandwidth data is pulled from a Linux router, filtered down to the target data using ‘grep’, and sent over the serial connection by a Perl script. Since the meter itself is just waiting for serial data, alterations to the router’s scripting make it easy to represent a count of unread emails, tweets, or whatever data your code can scrape.

[Thanks Ben]