Choosing A ‘Scope: Examining Bandwidth

October 5, 2016 by Jenny List 72 Comments

A few weeks ago I asked the Hackaday community for some help and advice in buying a new budget oscilloscope. Thank you very much to those of you who responded both here online and in person among my friends closer to home. I followed the overwhelming trend in the advice I received, and bought myself a Rigol DS1054z, an instrument with which I am very happy. It’s a nominally a 50 MHz scope, but there’s a software hack that can bring it up to 100 MHz. How fast can it go?

My trusty Cossor, its 2 MHz bandwidth as yet unverified.

This question became a mini scope-shootout after a conversation with my Hackaday colleague [Elliot] about measuring oscilloscope bandwidth, and then my fellow Oxford Hackspace members producing more than one scope for comparison. You know who you are, thank you. I found myself with ready access to several roughly equivalent models and one very high-end one in specification terms representing different strata of test equipment manufacture, and with the means to examine their performance.

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The New York Public Library Built A Reading Railroad

October 5, 2016 by Kristina Panos 25 Comments

What’s the best way to quickly move books from a vast underground archive to the library patrons who want to read them? For the New York Public Library (NYPL), it used to be an elaborate conveyor belt system. But the trouble with those is that the books will fall right off of them on a vertical run. What the NYPL’s gargantuan flagship library on 5th Avenue needed was a train to shuttle the books around. This week, as the majestic Rose Main Reading Room reopens after renovation, the train will leave the station.

From January to August 2016, workers retrofitted the existing conveyor belt infrastructure to support 950 feet of shiny, winding track. ‘Train’ is a bit of a misnomer because the cars travel singly. The double-track system traverses eight floors of library from the underground archive to any of the 11 designated stops. There are 24 book cars at present. Each one can hold about 30 pounds of books and travels at about 75 feet per minute.

In order to move between floors economically, some sections of track are completely vertical. How do the books stay in there? Simple—the cargo hold pivots on a gimbal. Sensors along the track make it easy to keep tabs on the cars, which are separated by a 15-second buffer to avoid collisions and mishaps. Click past the break for a sped-up demonstration. For you purists out there, we’ve also embedded the full, silent, real-time version that clocks in at nearly five minutes.

We like all kinds of trains around here, from the subterranean to the scientifically derailed.

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Transmitting Analog TV, Digitally

October 5, 2016 by Elliot Williams 14 Comments

If you want to really understand a technology, and if you’re like us, you’ll need to re-build it yourself. It’s one thing to say that you understand (analog) broadcast TV by reading up on Wikipedia, or even by looking at scope traces. But when you’ve written a flow graph that successfully transmits a test image to a normal TV using just a software-defined radio, you can pretty easily say that you’ve mastered the topic.

[Marble] wrote his flow for PAL, but it should be fairly easy to modify it to work with NTSC if you’re living in the US or Japan. Sending black and white is “easy” but to transmit a full color image, you’ll need to read up on color spaces. Check out [marble]’s project log.

Hackaday has another hacker who’s interested in broadcasting to dinosaur TVs: [CNLohr]. Check out his virtuoso builds for the ATtiny and for the ESP8266.

(Yes, the headline image is ~~one of his earlier trials with black and white~~ from Wikipedia — we just like the look.)

Hackaday Prize Entry: Making A Book Reader That Can Survive Kindergarten

October 4, 2016 by Gerrit Coetzee 5 Comments

[atomicthomas] is a dedicated teacher. One only has to look at the work he’s been putting into book readers for for the past sixteen years. With hardware like the Pi Zero threatening cheap computers just over the supply chain horizon, he’s begun to set his sights higher.

It all started with headphones and audio tapes. For all of us who got to use tapes and school headphones, we know the flaws with this plan. Nothing lasted the sticky and violent hands of children for long. When video recordings of book became available, DVD players suffered similar fates.

So, he began to rip his tapes and DVDs to his computer. However, the mouse has a warning about small parts on it for a reason, and didn’t last long either. So, he built a computer with arcade buttons and a Raspberry Pi. This one ran a heavily simplified version of a media manager and worked well. Even the special needs children had no problem navigating. A second exploration with an iMac and a Nintendo controller worked even better. Apparently all five year olds instinctively understand how to use a Nintendo controller.

Using the user test data, in his most recent iteration he’s working on a sub-twenty-dollar reading computer in a Nintendo controller. It’s not the most technically in depth hack we’ve ever covered, but it certainly ranks up there for harsh environments.

Hello 3D Printed Dolly

October 4, 2016 by Al Williams 15 Comments

[Ivan] likes to take time lapse videos. Using his 3D printer and a stepper motor he fashioned a rig that allows him to control the camera moving any direction on a smooth floor.

The dolly has a tripod-compatible mounting plate and scooter wheels. An Arduino runs the thing and a cell phone battery provides power. A pot sets the speed and [Ivan] provides code for both a linear pot, which he suggests, and for a logarithmic pot, which he had on hand. You can see a video of the results below.

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The Art Of Making A Nixie Tube

October 4, 2016 by Gerrit Coetzee 74 Comments

Three years ago we covered [Dalibor Farnby]’s adventures in making his own Nixie tubes. Back then it was just a hobby, a kind of exploration into the past. He didn’t stop, and it soon became his primary occupation. In this video he shows the striking process of making one of his Nixie tubes.

Each of his tubes get an astounding amount of love and attention. An evolution of the process he has been working on for five years now. The video starts with the cleaning process for the newly etched metal parts. Each one is washed and dried before being taken for storage inside a clean hood. The metal parts are carefully hand bent. Little ceramic pins are carefully glued and bonded. These are used to hold the numbers apart from each other. The assembly is spot welded together.

In a separate cut work begins on the glass. The first part to make is the bottom which holds the wire leads. These are joined and then annealed. Inspection is performed on a polariscope and a leak detector before they are set aside for assembly. Back to the workbench the leads are spot welded to the frame holding the numbers.

It continues with amazing attention to detail. So much effort goes into each step. In the end a very beautiful nixie tube sits on a test rack, working through enough cycles to be certified ready for sale. The numbers crisp, clear, and beautiful. Great work keeping this loved part of history alive in the modern age.

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A Quickly-Hacked-Together Avalanche Pulse Generator

October 4, 2016 by Jenny List 28 Comments

There are times when you make the effort to do a superlative job in the construction of an electronic project. You select the components carefully, design the perfect printed circuit board, and wait for all the pieces to come together as they come in the mail one by one. You then build it with tender care and attention, printing solder paste and placing components by hand with a fastidious attention to detail. There follows an anxious wait by the reflow oven as mysterious clouds of smoke waft towards the smoke detector, before you remove your batch of perfect boards and wait for them to cool.

Alternatively, there are other times when you want the device but you’re too impatient to wait, and anyway you’ve only got half of the components and a pile of junk. So you hack something a bit nasty together on the copper groundplane of a surplus prototype PCB in an evening with ‘scope and soldering iron. It’s not in any way pretty but it works, so you use it and get on with your life.

Our avalanche pulse generator schematic. The pulse generator itself is the single 2N3904 on the right.

When you are a Hackaday writer with some oscilloscope bandwidths to measure, you need a picosecond avalanche pulse generator, and you need one fast. Fortunately they’re a very simple circuit with only one 2N3904 transistor, but the snag is they need a high voltage power supply well over 100 V. So the challenge isn’t making the pulse generator, but making its power supply.

For our pulse generator we lacked the handy Linear Technologies switcher used by the avalanche pulse generator project we were copying. It was time for a bit of back-to-basics flyback supply creation, robbing a surplus ATX PSU for its base drive transformer, high voltage diode and capacitor, and driving it through a CRT line output transistor fed by a two-transistor astable multivibrator. Astoundingly it worked, and with the output voltage adjusted to just over 150V the pulse generator started oscillating as it should.

We’ve looked at avalanche pulse generators once before here at Hackaday, and very recently we featured one used to measure the speed of light. We’ll be using this one tomorrow for a ‘scope comparison.