VIDEO: oscilloscope (edited post)

FreddyUnreal · 2021-05-27T13:55:41.854Z

Can someone explain what MHz range is acceptable and what limitations lower or higher MHz scopes would have? I’ve seen scopes as low as 15MHz. I am a total noob to this and only has piqued my interest as this thread was rejuvenated.

evanh41 · 2021-05-27T14:06:26.739Z

On proper scientific oscilloscopes, the bandwidth is generally quite high, so high that you can do what is called “scan processing”, where you can visibly recall an image over an xy display and contort into what’s known as the “rutt etra” effect.

It’s possible on the vectrex, but tends to muddy up and filter out. But any old eurorack oscillator or audio will be perfectly suitable.

evanh41 · 2021-05-27T14:08:03.851Z

For reference on oscillographics/ vector synthesis, there’s a whole book on the subject and how to interface.

https://macumbista.net/?page_id=5711

FreddyUnreal · 2021-05-27T14:12:33.244Z

Thanks for the explanation! So if I’m understanding correctly the bandwidth size for audio or CV we would use in general can be relatively low? Is 15Mhz too low? Found one for pretty cheap.

PekeDorty · 2021-05-27T14:22:21.584Z

Vector Hack Festival

YouTube

Vector Hack Festival

Vector Hack is the biannual international festival devoted to experimental analogue vector graphics. Vector Hack aims to gather artists creating experimental audio-visual work for oscilloscopes, lasers and drawing machines to share ideas and develop...

Seems like a superb youtube channel / festival for inspiration / knowledge etc.

evanh41 · 2021-05-27T15:00:25.244Z

yesssss. the vectorhack channel, festival and community around it is incredible.

I always reference back to some of those talks, and actually had a chance this last year to exhibit some of my work in Croatia for the festival.

subduct · 2021-05-27T16:08:46.756Z

Thanks @PekeDorty @evanh41, so I’ve got 2xBNC to RCA female adapters, and I’ve got twin RCA to 3.5mm stereo. I’m going to plug any sound source (phone probably) into the XY channels on the scope with this and I should see vertical/horizontal traces from playing any music?
Or do I need to feed it with something more specific?

[EDIT] OR - is there a way just to get the scope to put out some test traces without connections, that’s all I need really

I don’t think I can test it with the probes, neither of us having any circuits/boards/electronics projects…

Lots of resources for me to read, thanks to all who have posted since my necro-revival. Elektronauts shows why it’s my favourite forum once again.

[EDIT 2] - and this video gives me my answer, this should work. I really should learn to finish researching BEFORE posting in over-excitement

https://www.youtube.com/watch?v=vrCjeQGavSE

Bilzc10

3 years ago (edited)

If anyone wants to connect their computer to their oscilloscope, instead of soldering your probes to a 3.5mm jack, buy 2 BNC (male) to RCA adapters, put them in the BNC connectors on the oscilloscope that correspond with X and Y. Then buy an RCA to 3.5mm adapter, which will take a 3.5mm input, and split it into a left and right RCA output, which then plug into the BNC to RCA adapters. The 3.5mm jack can be plugged into any audio source, and the sound will show on the oscilloscope

evanh41 · 2021-05-27T16:36:30.405Z

Yea you got it. It’s all voltage. Have fun.

subduct · 2021-05-27T16:41:01.570Z

evanh41:

Have fun.

Already am, thanks!

Jukka · 2021-05-27T16:48:29.868Z

FreddyUnreal:

Is 15Mhz too low?

This specification has to do if you are using the scope to plot voltage levels versus time. To do the drawings like you’ve seen above you need to use the scope in the X Y mode. Think of it like an Etch-A-Sketch, with two separate signals going to the two knobs. What gets drawn on the EAS has to do with the rhythmic frequency relationships of the two signals.

subduct:

playing any music?
Or do I need to feed it with something more specific?

What you’ll want to feed the X an Y are signals much less complex than music, or all you’ll get is a hash. But you also want feed it something more complex than two harmonically related sine waves, though that’s fine, you’ll get a nice lissajous pattern from that. If you have one signal that is varying at audio rates relative to the other, that will allow you to paint interesting images on the screen. Patching modular gear is one way to generate two signals with unusual repetitive voltage relationships to each other. Adding some noise to a signal fuzzes stuff up and paints more solid regions.

Modular simulators like VCV Rack is another, and you can use the scopes built in to that software. Plus then you can add color to it all, check out this video:

BTW: 15 MHz is 15 million cycles per second. That’s the rate the scope is able to distinguish. Audio goes to 20 thousand cycles per second. Big difference. So to see a wave on an voltage-time plot you turn a dial on the scope to slow your display rate way-way down.

ADDED: Another way to generate these sorts of images is to use a spread sheet and somehow (it’s up to you how) generate two columns of numbers that have a relationship to each other and plot that in XY. It’s basically the same thing, just done in different way.

image590×366 74.8 KB

PekeDorty · 2021-05-27T18:02:51.671Z

Jukka:

generate two columns of numbers that have a relationship to each other and plot that in XY. It’s basically the same thing, just done in different way.

could you rephrase / explain it like I‘m 5?

blurrghost · 2021-05-27T19:22:31.702Z

There’s a super low budget diy-ish device you can make that will give you more or less the same results. Sort of an audio responsive pseudo-scope toy made from old crt devices (though some types work better than others) and it can even be applied to some kinds of projectors though those are getting hard to find.
It’s a fairly simple mod and the principle is neat, just don’t touch the part that kills you. No, really, that’s a thing. I don’t want to derail the thread but if people want I can explain it and it’s small handful of variations on the same basic theme.

subduct · 2021-05-27T20:08:59.291Z

Jukka:

Patching modular gear is one way to generate two signals with unusual repetitive voltage relationships to each other.

This is also my plan.

Jukka · 2021-05-27T21:06:11.033Z

PekeDorty:

could you rephrase

Sure PeteDorky — but you’re a very precocious 5 y.o.

A computer spreadsheet is a program that lets you generate volumes of data, based on other data and mathematical formulas, and then it can make pictures from that data. One way to make a picture is draw and connect a series of points that you place on an X, Y graph.

If the X’s are generated from Sine (a), and the Y’s are generated by Sine (3a), the graph will be a lissajous curve with three bumps on one side and one bump on the other.

To see what that lissajous curve looks like go to this web-site and enter 1 for a, and 3 for b. This web-site is even better for experimentation for making lissajous curves than using a spreadsheet. But you can do other more complicated formulas with a spreadsheet. There are many other programs that allows you to enter mathematical formulas and make graphs as well.

Try entering 2 for a, and 3 for b.

You could set up an analog modular system that would do the calculations just like at this web-site, and be able to actively modulate the various parameters you see here, and generate the data to be graphed on an oscilliscope. It is sometimes useful to think of an analog modular system as an analog computer.

FreddyUnreal · 2021-05-28T13:54:44.451Z

This is a great explanation. Thank you for taking the time. This gets more intriguing by the day.

PekeDorty · 2021-05-30T21:04:42.955Z

Hmm… yeah nice shapes can be created – but you added that picture which I wouldn’t know how to generate with a spread sheet or combined sine functions… so the spreadsheet part is not yet clear I guess…

Maybe I should do analog psychedelic (neon wool) stringart instead

Cocker · 2021-06-14T14:54:25.302Z

I think it was just a google search at the time. They are likely DIY jobs

I don’t think it would be too difficult to try and make some DIY cables to suit your need. So long as you have the right tools for the job

subduct · 2021-06-14T15:21:59.381Z

In the end I got a couple of BCN to phono adapters and a twin phono to 3.5mm stereo cable - which I think is what’s in this image looking more closely! Thanks for the reply. The 2225 is sat in my cupboard waiting for me to do something creative with it

TrabanT · 2021-06-15T09:21:52.579Z

I have to say, coming back to this after 7 years is quite cool : )

subduct · 2021-06-15T13:36:32.695Z

Well pleased I found this topic. This forum is a true gold mine of resources, creativity and enthusiasm. Hopefully I can add to the thread over the coming months!