An Oscilloscope on your Wrist

osc-watch2

Calculator watches were the Geek cred of the 80’s. Today everyone is getting smart watches. How can the hip Geek stay ahead? [Gabriel Anzziani] to the rescue with his Oscilloscope Watch! [Gabriel] has made a cottage industry with his micro test tools. We’ve featured his Xprotolab and Xminilab on here on Hack a Day more than once. The Oscilloscope Watch basically takes all the features of the Xprotolab and squeezes them down into a wrist watch.

The Oscilloscope Watch includes an oscilloscope, a logic analyzer, an arbitrary waveform generator, and of course it tells time.  The Oscilloscope Watch’s processor is the AVR XMega128.  [Gabriel] has even included a link to the schematics (PDF) on his Kickstarter page. We really like that 3D printed case, and hope [Gabriel] opens up his CAD designs for us to work with.

Like its predecessors, the Oscilloscope watch won’t be replacing your Tektronix scope, or even your Rigol. Much like a Swiss army knife or Leatherman tool, the Oscilloscope Watch packs a bunch of tools into a small package. None of them are as good as a full-sized tool, but in a pinch they will get the job done. If you are wondering where the probes connect. [Gabriel] states on the Kickstarter page that he will design a custom 9 pin .100 connector to BNC adapter to allow the use of standard probes.

The screen is the same series of Sharp Memory LCD’s used in the Pebble watch. [Gabriel] chose to go with the FPC version of the Sharp LCD rather than the zebra connector.  We’ve learned the hard way that those flex circuits snap at the LCD glass after only a few flexes. Hopefully this won’t impact the hackability of the watch.

Connecting an old scope to a computer

Scope

A friend of [Michael]‘s said his company was getting rid of some old lab equipment and asked him if he wanted a very large and very old digital storage oscilloscope. A ‘hell yes’ and we’re sure a few beers later, [Michael] found an old Gould 200 MHz four-channel scope on his bench. Even 20 years after its production it’s still a capable tool, but the serial ports on the back got [Michael] wondering – would it be possible to plot the screen of the scope on his computer?

The scope has three ports on the back – GPIB, miscellaneous I/O, and RS423. The latter of those ports is similar enough to RS232 that a USB to Serial converter just might work, and with the help of a null modem cable and a terminal, [Michael] was able to connect to this ancient scope.

In the manual, [Michael] found a the serial commands for this scope. The most useful of these is a command that prints out the contents of the scope’s trace memory as a series of 1-byte integers. With a short bit of PERL programming, [Michael] can create a PDF plot of whatever is on the scope’s screen. It’s formatted perfectly for Gnuplot, MATLAB, or even Excel.

Awesome work, and especially useful given these old scopes are slowly making their way to a technological boneyard somewhere.

Write an essay, win a Tektronix scope

tektronix_scope_giveaway

Want a new scope for your hacking pleasures? How about one that rings in at $3650? That price tag makes us cringe, which is why we’re working on our 1k word essay to win one. The Tektronix MSO2024B pictured above is the top scope in its family and there’s more than enough features to start the drool flowing. Need more motivation? Check out the demo/advertising video below which walks through an overview of what the scope has to offer.

The contest — sponsored by EETimes and Tektronix — seeks to reward the best story about fixing a product that was disappointing on delivery but awesome when you got done hacking on it. Your thousand words or less are due by October 26th along with a fifty word bio about yourself, with the winner announced on Halloween. Be warned, you must register an account to qualify But we hit their daily article viewing limit while writing this post so you may need to log in just to read about the contest. Or clear their cookies… we are a hacking website after all.

They’re only giving away one scope. So don’t put this one off. Start polishing your totally bogus legit story about how you fixed something using mad engineering skills.

[Read more...]

Bode plots on an oscilloscope

bode

Bode plots – or frequency response graphs – are found in just about every piece of literature for high-end audio equipment. It’s a simple idea, graphing frequency over amplitude, but making one of these graphs at home usually means using a soundcard, an Excel spreadsheet and a multimeter, or some other inelegant solution. Following a neat tutorial from [Dave Jones], [Andrew] came up with a very simple way to make a Bode plot in real-time with an oscilloscope, a microcontroller, and a few off-the-shelf parts.

The basic idea behind [Dave Jones]‘ impromptu Bode plotter is to configure a frequency generator to output a sine wave that ramps up over a period of time. Feed this sine wave through a filter, and you have amplitude on the vertical axis of your ‘scope and frequency on the horizontal axis. Boom, there’s your Bode plot.

[Andrew] did [Dave] one better by creating a small circuit with an Arduino and an AD9850 sine wave generator. Properly programmed, the AD9850 can ramp up the frequency of a sine wave with the Arduino outputting sync pulses every decade or octave of frequency, depending if you want a linear or log Bode plot.

It’s a nifty little tool, and when it comes to building test equipment from stuff that just happens to by lying around, we’ve got to give it up for [Andrew] for his really cool implementation.

 

Playing with an oscilloscope you’ll (probably) never own

We’ll have to admit that we were really jealous when [Shahriar] sent us a video he made, in which he casually explains how a $500,000 160GS/s 62GHz oscilloscope works and then starts playing with it.

Even though you need to be quite familiar with electronics to fully understand the oscilloscope’s inner workings, [Shahriar]‘s step by step explanation is still approachable for those who only understand the basics.

In the first half of the video he uses the manufacturer’s documentation which contains the oscilloscope block diagrams, so you’ll also learn about:

  • timer interleaved Analog to Digital Converters (ADCs), which allows you to increase your input sampling rate by using several of them
  • phase-locked loops, which use a reference clock to generate a much faster clock signal
  • custom made dies and the materials used for high frequency electronic components

In the second half of the video [Shahriar] connects a pseudo random binary sequence generator and uses the oscilloscope to make several measurements that you’d typically want to know for high speed signals (jitters, eye quality factor…). He later performs a small experiment where he up-converts the frequency components of two random 3.12Gbit/s signals and tries to recall each original signal using the oscilloscope functions, making this part of the video a bit harder to keep up with.

Bench equipment tip: Screenshot of old oscilloscopes

oscillocam-oscilloscope-camera-accessory

Here’s a quick tip on capturing the output of oscilloscopes that don’t have that native feature. [Paulo Renato] used a cookie tin as a camera cowl for capturing CRT oscilloscope screenshots.

We figure if you’ve got any kind of functioning oscilloscope you’re lucky. And although it’s nice to pull down the measurements to your PC on the newer models, the results [Paul] gets with this rig are still satisfactory. The plastic cookie box he used blocks out ambient light while holding the camera at a consistent focal length. He used some flat black spray paint to make sure the obnoxious yellow plastic didn’t interfere with the image, then drilled a hole which fits tightly around his camera lens.

You’ll need to monkey with the exposure settings to get the best image. But once you’ve got it dialed in it should be the same every time you want to take a picture of the screen.

Measuring tiny current with high resolution

measuring-microamps-at-3MHz

[Paul] knew that he could get an oscilloscope that would measure the microamp signals with the kind of resolution he was after, but it would cost him a bundle. But he has some idea of how that high-end equipment does things, and so he just built this circuit to feed precision data to his own bench equipment.

He’s trying to visualize what’s going on with the current draw of a microcontroller at various points in its operation. He figures 5 mA at 2.5 mV is in the ballpark of what he’s probing. Measurements this small have problems with noise. The solution is the chip on the green breakout board. It’s not exactly priced to move, costing about $20 in single quantity. But when paired with a quality power supply it gets the job done. The AD8428 is an ultra-low-noise amplifier which has way more than the accuracy he needs and outputs a bandwidth of 3.5 MHz. Now the cost seems worth it.

The oscilloscope screenshot in [Paul's] post is really impressive. Using two 1 Ohm resistors in parallel on the microcontroller’s power line he’s able to monitor the chip in slow startup mode. It begins at 120 microamps and the graph captures the point at which the oscillator starts running and when the system clock is connected to it.