Cheap Scope Troubleshoots Commodore

November 8, 2022 by Al Williams 17 Comments

[Adrian] had a Commodore computer to fix and decided to see how his latest tiny portable scope would work. He paid $57 for the tiny little test instrument although the current price seems higher. It claims to have 120MHz bandwidth along with 500 megasamples per second. There are several versions with different claimed specs, but we did find a similar device for under $60. You can see the unboxing and how it worked in the video below.

Of course, these kinds of instruments often overstate their specs, and [Adrian] was also suspicious. One odd feature of the device is it can echo its output to an NTSC video output so you can send the screen to an external monitor.

Continue reading “Cheap Scope Troubleshoots Commodore” →

A Pi Pico Oscilloscope

November 6, 2022 by Jenny List 40 Comments

At the budget end of the oscilloscope range lie the so-called pocket ‘scopes. About the size of a deck of cards, they combine a microcontroller and an LCD screen to make an instrument with a bandwidth in the tens of kilohertz and a not-too-sparkling performance. They’re something of a toy, but then again, if all that’s needed is a simple ‘scope for audio frequencies, they make a passable choice in a small package. Now [jgpeiro] has made one which is light years ahead of the toy kits, using a Raspberry Pi Pico, a 100 MHz ADC, and an effort to design a better input circuit.

At its simplest this could be a straightforward op-amp and ADC circuit feeding the Pico, but instead it has multiple stages carefully designed to offer the full bandwidth, and with gain, offset, and trigger settings being set by a series of DAC chips under software control. This and the decent bandwidth make this a much more viable oscilloscope, and one we’d like to see further developed.

By comparison, we took a look at the best of the competition a few years ago.

A small green circuit board with a tiny OLED display

An Oscilloscope Trigger For Vintage Video Processors

October 18, 2022 by Chris Wilkinson 8 Comments

Working on retro computers is rarely straightforward, as [ukmaker] recently found out while designing a new display interface. Their oscilloscope was having trouble triggering on the video signal produced by older video circuitry, so they created the Video Trigger for Retrocomputers.

The Texas Instruments TMS9918 video display controller was used across a range of 1980s game consoles and home computers, from the well-known ColecoVision to Texas Instruments’ own TI-99/4. Substantial retro computing heritage notwithstanding, the video output from this chip was (for reasons unknown) not quite compatible with the Hantek DSO1502P oscilloscope. And without a better understanding of the video signal, it was difficult to use the chip with newer TFT displays, being designed for CRT televisions with more forgiving NTSC tolerances.

Maybe a different scope would have solved the problem, but [ukmaker] had a feeling that the ‘scope needed an external trigger signal. The Video Trigger project uses a LM1881 sync separator to tease out the horizontal and vertical sync signals from the vintage video chip, with the output piped into an ATmega 328P. Along with a smattering of discrete components, the ATmega aids the user in selecting which line to frame a trigger on, and the slope of the horizontal sync signal to align to. A tiny OLED display makes configuration easy.

If this has piqued your interest, [ukmaker] also has a great write-up over on GitHub with all the gory details. Maybe it will help you in your next vintage computing caper. Having the right tool can make all the difference, like this homebrew logic meter for hobby electronics troubleshooting. Or if you want to know more about the mystical properties of analog NTSC video, we’ve covered that, too.

2022 Cyberdeck Contest: The Oscilloscope Deck

September 30, 2022 by Jonathan Bennett 27 Comments

When [Jak_o_Shadows] Siglent Oscilloscope died, he didn’t just mourn the loss, he saw an opportunity. See, he had a Raspberry Pi 400 already set aside for a cyberdeck build, and he just scored a novel case. Most of the insides of the old scope came out, but the screen and control knobs live on in the new build. An HDMI-to-LVDS adapter brought the screen back to life, and the control knobs are a work-in-progress. Added to the case are some fun goodies, like a LimeSDR, connected to the old scope inputs. A PL2303 is wired to the serial port, making that functional, too. It’s a very nice touch that the build retains the original scope’s functions this way.

There’s plenty of 3d-printed goodness, like some internal brackets to hold things in place. The real star of the show is a 3d-printed hinge, holding the scope and Pi 400 together and making the whole package portable. There’s a neat tip, too, in that the Pi 400 has a huge integrated heat sync under the keyboard. It’s just a sheet of metal, so you can drill and tap it as mounting points. Cool!

This is a nifty build, and certainly a worthy deck for jacking-in to whatever you’re working on. And re-purposing an oscilloscope is a nice aesthetic. If [Jak_o_Shadows] can just get the front array of buttons and knobs working with his STM32, this will be a killer deck, the envy of console cowboys everywhere.

Better Scope Measurements

September 22, 2022 by Al Williams 6 Comments

There was a time when few hobbyists had an oscilloscope and the ones you did see were old military or industrial surplus that were past their prime. Today you can buy a fancy scope for about what those used scopes cost that would have once been the envy of every giant research lab. However, this new breed of instrument is typically digital and while they look like an old analog scope, the way they work leads to some odd gotchas that [Arthur Pini] covers in a recent post.

Some of his tips are common sense, but easy to forget about. For example, if you stack your four input channels so each uses up a quarter of the screen, it makes sense, right? But [Arthur] points out that you are dropping two bits of dynamic range, which can really jack up a sensitive measurement.

Continue reading “Better Scope Measurements” →

Why Didn’t We Think Of Making A Remote Trigger Button?

August 21, 2022 by Jenny List 44 Comments

One of the many functions a digital oscilloscope offers over its analog ancestors is a trigger button. Alongside the usual electronic means of triggering the instrument, you can reach over and press a button to “freeze-frame” the action and preserve the trace. Sometimes doing it repeatedly it can become a chore to reach for the ‘scope. That’s where [Kevin Santo Cappuccio]’s remote trigger button comes in.

The button itself is about as simple a hack as it gets. The ‘scope was carefully dissected and some fine wires laid from the contacts within the front panel to a connector on the case. From there a cable goes to a box with a momentary action button switch. Plug in the box, and you can trigger the ‘scope from a distance!

We have to admit to rather admiring this hack, as needing to trigger the ‘scope is a well-known problem here. It’s easy to stab the wrong button and lose what you are looking for, so we’re rather surprised we didn’t think of this one ourselves. But then again from another viewpoint, it involves dissecting an expensive instrument which is best left unmolested. Perhaps manufacturers should consider adding this functionality.

This may be the most straightforward oscilloscope hack we’ve shown you, but it’s certainly not the first.

Balancing A Motor With An Oscilloscope

June 18, 2022 by Dan Maloney 17 Comments

With all things in life, one must seek to achieve balance. That may sound a little like New Age woo-woo, but if you think it’s not literally true, just try tolerating a washing machine with a single comforter on spin cycle, or driving a few miles on unbalanced tires.

Anything that rotates can quickly spin itself into shrapnel if it’s not properly balanced, and the DIY power tools in [Matthias Wandel]’s shop are no exception. Recent upgrades to his jointer have left the tool a bit noisy, so he’s exploring machine vibrations with this simple but clever setup. Using nothing but a cheap loudspeaker and an oscilloscope, [Matthias] was able to characterize vibrations in a small squirrel-cage blower — he wisely chose to start small to validate his method before diving into the potentially dangerous jointer. There was quite a lot to be learned from the complex waveforms coming back from the transducer, analysis of which was greatly helped by the scope’s spectrum analyzer function. The video below shows the process of probing various parts of the blower, differentiating spectral peaks due to electrical noise rather than vibration, and actually using the setup to dynamically balance the fan.

We’d rate this as yet another handy shop tip from [Matthias], and we’ll be looking out for the analysis of his jointer. Want to do the same but you don’t have an oscilloscope? No problem — an earbud and Audacity might be all you need.

Continue reading “Balancing A Motor With An Oscilloscope” →