I built a light that reacts to radio waves [video]
159 points
4 hours ago
| 19 comments
| youtube.com
| HN
https://rootkid.me/works/spectrum-slit
TrackerFF
31 minutes ago
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Cool project. I was going to say, the end resulting light should be a pretty saturated spectrum, given that many RF sources just keep pumping out waves, and the those waves propagating and bouncing around.

I think one fun application would be a light which represents your wi-fi strength around the house. Obviously in a smaller apartment that's really not a problem, but in larger houses it would be fun to see.

Another application would be to find hidden RF sources / leaks. I have a home recording studio, and for the life I could not find some RF source that kept adding noise / interference. I could roughly detect the frequency of the noise, but not its origin. I guess if I had a couple of RF sensors I could try to triangulate my way to it.

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fnands
10 minutes ago
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Very cool! I was having a conversation with my colleagues yesterday about building something to detect when you get scanned by a SAR (synthetic aperture radar) satellite (we're in earth observation), but you'd have to get a directional antenna to not be drowned out by terrestrial radio signals.
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mrtksn
3 hours ago
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It’s beautiful. I think I’ve seen something similar in a Ukraine war video where they use a device that lights up on specific frequencies that drones use.
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lucid-dev
3 hours ago
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FANTASTIC!!

I was just thinking about this the other day, and wondering about directionality...

For example, if you had a camera facing a space, and the receiving antenna was within that space... and you were able to (somehow?) from the antennas perspective, see the "direction" the frequency was coming from..

And then map the different specific frequencies within the desired bandwidth to colors... and of course intensity map like you have in the slit device..

And then "look through the camera"... you would see a live three dimensional overlay of all signals within range (colored!) "interacting" with the antenna... but kind of more the "looking through the camera" sort of view, like you could "see" how those waves were interacting..

And then wouldn't it be interesting to put a tin-foil hat to one side of the attennas.. and see how the waves change in real time... etc.!!!

(I guess it takes three antennas, to triangulate the field? Maybe all three can still be mounted on a single device in close proximity?)

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mzhaase
2 hours ago
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phrotoma
4 minutes ago
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diimdeep
33 minutes ago
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The title is: This ESP32 Antenna Array Can See WiFi

And every time I see something like this I like to remind to myself and imagine what spherical grid of Starlink satellites linked by laser is really capable of instead of mere internet as it is advertised.

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amelius
1 hour ago
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This is sort of that idea with sound:

https://www.youtube.com/watch?v=jL2JK0uJEbM

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johanvts
2 hours ago
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If you buy three (or more) Phillips Hue bulps you can have them respond to motion detected by things moving around and disturbing the radio waves they use to communicate. So they must have pretty much the kind of map you want, but I dont know how easy it is to export it.
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ErroneousBosh
1 hour ago
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> and you were able to (somehow?) from the antennas perspective, see the "direction" the frequency was coming from..

You can kind of do that quite easily at low frequencies, by measuring the phase of signals coming in from a pair of aerials. If you put two aerials a quarter of a wavelength apart and switch between them very quickly at audio rate, then you'll get a tone when there's a difference in phase. If there's no tone the two signals are exactly in phase - the two aerials are exactly the same distance from the transmitter.

If you look on some police cars you'll see a group of four aerials about 15cm apart stuck to the roof which used to be used for "Lojack" style trackers.

There are a whole bunch of circuit diagrams floating around for doing this kind of thing, with the simplest being Ye Olde 555 timer and a couple of PIN diodes!

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amelius
1 hour ago
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All those inductors... Isn't there a cheaper way to drive those lights, e.g. using DC voltage+pwm?
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seszett
27 minutes ago
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Those inductors are cheaper than what PCBWay charged for making that wooden box, I don't think their cost matters much here.
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milleramp
3 hours ago
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Very cool, was there a conversion or look up table to convert db to gamma for more accurate human visualization?
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Surac
1 hour ago
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I once had a antenna with a lamp on it. It was used to detect best place for the radio. It just rectified the energy it received and used a very tiny light bulb
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cush
3 hours ago
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His other projects are so interesting. I love this one

https://rootkid.me/works/exhibit-a

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CrzyLngPwd
1 hour ago
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Oh, that is fantastic.

What would really finish it for me, though, is if, when the button is released, the device shows a website, with URL visible, with a photo of the criminal, with added facial recognition and lookup of social media to find their identity.

What fun!

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simgt
1 hour ago
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The narration is very nice. Any idea of what the data could be? He mentions that it's legal for him to store but illegal to sell abroad and ranges from "bad to very bad".
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ggm
3 hours ago
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I cannot find the YT video but an artist in residence did a short film with scratch-over of footage in an RF lab which tries to give a visual impression of the waves emitted by things present.

We're bathed in EMF. It's what light is, but aside from that we use electricity so much now, we're in a sea of radiation in other frequencies too.

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smellington
1 hour ago
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Very appropriate soundtrack too:

https://youtu.be/B_gLxVZuk60

Uranium by Radioactiveman

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01100011
1 hour ago
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A much simpler and less cool project would be to convert a slice of the RF spectrum into an RGB value with lowest frequencies mapped to red, highest to blue, and the resulting color being how we would perceive the mix.
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mock-possum
3 hours ago
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Incredibly cool. I was really hoping to see the more ‘edge’ cases - take the light out to the middle of nowhere, walk towards it and away from it with just your phone or a Bluetooth speaker, see it react to your approach. The bit at the end about it shifting over the course of the day is cool, but I wish the effect was more visually apparent - it mostly just looked like random noise the whole time to me.
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cush
3 hours ago
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The sounds were so cool -straight out of sci-fi movie.
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shawn10067
3 hours ago
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This is such a neat project. The idea of translating invisible radio waves into visible light is mesmerizing — it feels like giving your surroundings a new sensory dimension.
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mw67
3 hours ago
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Someone makes a kickstarter out of it please
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dyauspitr
3 hours ago
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This is fantastic. But the idea where you use a camera that can only see the wifi signals in the room like visible light is even more stunning. It would be even better if you could block out all light from the visible spectrum and only see the GHz band.
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segalord
3 hours ago
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I love your poetry on a phone project so muchhhh
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ebhn
3 hours ago
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Very cool!
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louwrentius
2 hours ago
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Let's call this what it really is: it's an art project. It's not 'just' a cool technical work.

[0]: https://news.ycombinator.com/item?id=46729428

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