Salvaged Scope Lets You Watch the Music

Everyone likes a good light show, but probably the children of the 60s and 70s appreciate them a bit more. That’s the era when some stereos came with built-in audio oscilloscopes, the search for which led [Tech Moan] to restore an audio monitor oscilloscope and use it to display oscilloscope music.

If the topic of oscilloscope music seems familiar, it may be because we covered [Jerobeam Fenderson]’s scope-driving compositions a while back. The technique will work on any oscilloscope that can handle X- and Y-axis inputs, but analog scopes make for the best display. The Tektronix 760A that [Tech Moan] scrounged off eBay is even better in that it was purpose-built to live in an audio engineer’s console for visualizing stereo audio signals. The vintage of the discontinued instrument isn’t clear, but from the DIPs and discrete components inside, we’ll hazard a guess of early to mid-1980s.  The eBay score was a bargain, but only because it was in less that perfect condition, and [Tech Moan] wisely purchased another burned out Tek scope with the same chassis to use for spares.

The restored 760A does a great job playing [Jerobeam]’s simultaneously haunting and annoying compositions; it’s hard to watch animated images playing across the scope’s screen and not marvel at the work put into composing the right signals to make it all happen. Hats off to [Tech Moan] for bringing the instrument back to life, and to [Jerobeam] for music fit for a scope.

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Soviet Portable Scopemeter Teardown

Browsing YouTube may prove to be your largest destroyer of productive time outside of Hackaday, once you have started looking at assorted Lincolnshire plumbers or young Ukrainians doing dangerous stunts it’s easy to lose an hour with very little to show for it. There is so much to divert our attention, it’s a wonder that any of us ever make anything!

So to ensure you lose a further quarter hour today, we’d like to bring you [Jesper Broe]’s demonstration and teardown of his latest oscilloscope. This might seem unpromising when we tell you it’s a single-trace model with a bandwidth of 10MHz, but don’t give up. This is a RIMEDA C1-112, a portable instrument made in Lithuania when the country was part of the Soviet Union, and its party piece is that it contains a digital multimeter with a vector display using the oscilloscope CRT.

We’re shown the compact device being unpacked, then put through its paces as an oscilloscope. It gives useful results above 10MHz, but it is visibly losing amplitude and eventually it has trouble triggering as the frequency increases. Interestingly all the controls work in the opposite direction to the ones you will be used to, anticlockwise rotation increases rather than decreases. Then we’re shown the multimeter function, which is compared to a modern DMM and found to be still pretty accurate after nearly three decades.

The ‘scope’s lid is then removed, and we see something of the logic boards that produce the digital display. A host of Soviet K155 series logic ICs are at the heart of it, and at the end of the video we’re shown a period review in Russian with a glimpse at the waveforms they produce to vector draw the figures.

Take a look at the video below the break, we’re sure you’ll agree it’s an instrument that many of us would still find useful today.

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Smartphone Bench Instrument Apps: Disappointment or Delight?

If you are interested in electronics or engineering, you’ll have noticed a host of useful-sounding apps to help you in your design and build work. There are calculators, design aids, and somewhat intriguingly, apps that claim to offer an entire instrument on your phone. A few of them are produced to support external third-party USB instrument peripherals, but most of them claim to offer the functionality using just the hardware within the phone. Why buy an expensive oscilloscope, spectrum analyzer, or signal generator, when you can simply download one for free?

Those who celebrate Christmas somewhere with a British tradition are familiar with Christmas crackers and the oft-disappointing novelties they contain. Non-Brits are no doubt lost at this point… the crackers in question are a cardboard tube wrapped in shiny paper drawn tight over each end of it. The idea is that two people pull on the ends of the paper, and when it comes apart out drops a toy or novelty. It’s something like the prize in a Cracker Jack Box.

Engineering-oriented apps follow this cycle of hope and disappointment. But there are occasional exceptions. Let’s tour some of the good and the bad together, shall we?

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Open Design Oscilloscope Could be (Almost) Free

If you could only own one piece of test equipment, it should probably be an oscilloscope. Then again, modern scopes often have multiple functions, so maybe that’s not a fair assertion. A case in point is the Scopefun open hardware project. The device is a capable 2-channel scope, a logic analyzer and also a waveform and pattern generator. The control GUI can work with Windows, Linux, or the Mac (see the video, below).

The hardware uses a Xilinx Spartan-6 FPGA. A GUI uses a Cypress’s EZ-USB FX2LP chip to send configuration data to the FPGA.  Both oscilloscope channels are protected for overvoltage up to +/- 50 V. The FPGA samples at 100 Mhz through a 10-bit dual analog-to-digital converter ( ADC ). The FPGA handles triggering and buffers the input before sending the data to the host computer via the USB chip. Each channel has a 10,000 sample buffer.

There are also two generator outputs with short circuit and overvoltage protection ( +/- 50 V ). Generator channels have 50 Ohm internal impedance and also operates via the GUI using the same USB chip. The FPGA generates signals at 50 Mhz using counters, algorithms, or simple waveform data and feeds a DAC.

A 16-bit digital interface can be set as inputs or outputs. The FPGA samples inputs at 100 MHz. The output voltage can be set, but inputs are 5 V tolerant.

According to the developer, you can build the scope from the information provided by using free sample chips from the various vendors, only paying for the small components and the cost of the PCB.

We’ve looked at several low-cost scope options before. Labtool even boasts some similar features.

Choosing A ‘Scope: Examining Bandwidth

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.
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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Ask Hackaday: Help Me Choose A ‘Scope

If there is one instrument that makes an electronic engineer’s bench, it is the oscilloscope. The ability to track voltages in the time domain and measure their period and amplitude is one akin to a light in the darkness, it turns a mere tinkerer with circuits into one in command of them. Straightforward add-on circuits can transform a basic oscilloscope into a curve tracer, frequency response display, and much more, and modern oscilloscopes offer a dizzying array of useful measurement features unimaginable to engineers only a few years ago. And I need your help to pick a new one.

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Yet Another Inductance Measuring Scheme

How do you measure the value of an unknown inductor? If you have an LCR bridge or meter, you are probably going to use that. If not, there are many different techniques you can use. All of them rely on the same thing my Algebra teacher Mr. Harder used to say back in the 1970’s: you have to use what you know to get what you don’t know.

[Ronald Dekker] must think the same way. He took a 50-ohm signal generator and a scope. He puts the signal output to about 20kHz and adjusts for 1V peak-to-peak on the scope. Then he puts the unknown inductor across the signal and adjusts the frequency (and only the frequency) for an output of 1/2 volt peak-to-peak.

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