Hellooooo!
I came across this earlier and thought something like this would look cool in a Kosmo responding to an audio input! For all of you smart people, how would you go about making something like this? I’m assuming it’s a raspberry pi?
3 Likes
You certainly could do something like that with a pi or even just a nano plus a suitable display module. It’s not much different than an oscilloscope module, and there’s a design for a nano based (Eurorack) scope module out there. Might want some kind of filtering on the input, and then it’s just a matter of getting the software to produce the kind of visuals you want.
1 Like
Thank you! I’m gonna pick up a raspberry pi and start experimenting!
Why pi? You can get a nano for under $4 and it’ll work just fine for this.
1 Like
I don’t think the nano will be capable enough of doing this at a very high refresh rate. Maybe something a bit more beefy like a ESP32 could be a good middle ground.
1 Like
It would be harder with a Raspberry Pi than an Arduino clone. The Pi doesn’t have any ADC (or DAC) pins so you’d have to add something in for that as well, and you’d end up getting a bit spendy. (I’m assuming you mean a ‘normal’ Pi and not a Pi Pico, which is a very different beast!)
I’ve got two go-to boards, and they’re both far cheaper than a Raspberry Pi and have the analogue inputs you’ll need. They’re also both 32-bit, run faster and have much more memory than the 8-bit Arduinos; you can program them using the Arduino IDE but you can also run CircuitPython on them, so you can have what I think is the nicest development experience when programming microcontrollers. (You may disagree with me, and I don’t mind you being wrong 
)
These are based on the RP2040 chip, same as the Raspberry Pi Pico. They’re almost identical in pinout to the Pi Pico - a couple of changes regarding the analogue inputs, so you get four instead of the three that the Pico has - plus a load more memory. Last time I bought some I paid about £2 a piece from AliExpress.
You can get clones of these from your favourite tat merchant for about the same price, I got five for £12 including shipping. These are based on the ESP32-S2, so there’s wifi and things included, and they also have a pair of 8-bit DAC pins so you can get ‘proper’ analogue outputs as well. (They need a little surgery to fix a design flaw to get one of them to work properly, though - I wrote that up here but my images are broken at the moment.)
ANYWAY. Either of those boards would be better than a regular Raspberry Pi by far. You’d then have to do something about buffering and biasing the signal if you want bipolar audio signals to be represented, of course…
1 Like
I’m not so sure a high refresh rate is really required for this. But that’s a judgement call.
1 Like
Arduino oscilloscope modules:
- Scope-o-Matic by @Jos
- OSGO by maasijam
- Oscilloscope and spectrum analyzer by Hagiwo
3 Likes
When using Scope-O-Matic I typically set the refresh rate so that I can see a few cycles of the wave I’m interested in. Given that a 50Hz cycle lasts 20 mS to be able to see a few you need maybe 100 mS refresh rate. If however you want to see the effect of an LFO on a VCO, you typically want to see many more cycles. In that case the amount of ram the mpu has available is the limiting factor and you need to take aliasing of the signal by the display into account. In the current implementation the lowest refresh rate of my nano based scopes is 200mS, which often is too short for seeing such things.
1 Like
Thank you guys! This would definitely just be for looks over function, so I think a higher refresh rate would be ideal. It definitely does not need to be an oscilloscope!
Here’s a video example of what I’m after.
If you’ve never seen his work, it’s amazing
2 Likes
You could go the DSO route, plum audio have a simple convertion kit for a DSO150 scope which would be easily adapted to Kosmo.
I built a few of the OSGO modules and they are nice and can be set to a refresh rate that looks presentable as eyecandy, although, something a little bigger than the tiny screen it uses would be very nice.
There is another similar module that uses a round screen, although it isnt made for euro level volume, it could probably be adapted, however I can’t recall where I saw it…
If you actually want a Kosmo scope, here’s mine based on a DSO138, which is out of production but you probably can still buy one
But for a visualizer you probably would want something different.
2 Likes
I’ve been tinkering with an old 2" b&w intercom CRT as a visualiser. While frustratingly easy to break I still think I’m onto something. Especially as the tinted resin lenses I’ve been playing with go so well with a crt. I’d appreciate any good/useful CRT sources or ideas. Cheers
1 Like
Hey Everybody,
a while ago i saw this: https://www.youtube.com/watch?v=bO-DWWFolPw
The way i understood it, it might be enough to connect an audio signal to the right input pins of an old CRT television… am i right? 
4 Likes
I saw that! It’s a superb design choice. My son asked me to make him a desktop assistant and an analogue line like this is a great focus.
I did get the opportunity to look inside some keyboard controllers that Love Hulten made a little while ago. There was a dedicated board for the screen graphics, rather than a Pi. It looked like a commercially manufactured product, with an audio input and a video output. Two potentiometers - one to set the sensitivity to audio, one to select the pattern type being displayed.
3 Likes
Do you have any more information on the dedicated board you mentioned?
1 Like
Not sure if it had a manufacturer’s name!
1 Like