[Idea sharing] Audio Controlled LEDs - Page 1
Forum section: electronics / projects

author: krd777
author_rank: Contributor
timestamp: July 20, 2010, 08:26:35 pm
content: Hi everyone!One of these days a friend showed me a video in Youtube about a circuit that would process an audio signal and light 3 LEDs. But those LEDs would be controlled by frequency. One for low frequencies, another for middle frequencies and the last for high frequencies. And since the video author wasn't giving out any schematics, he asked me if I could do it. So I did a sketch today and will try to get it working tomorrow. Since someone might want this too, I thought sharing would be cool! So here it is, and sorry it is written by hand, but didn't feel like using the pc just for sketching. I didn't give values to components because I haven't decided it myself. But I'll post here the final circuit after it is done and working.Any suggestions and/or critics are very welcome!

author: migsantiago
author_rank: Frequent Contributor
timestamp: July 20, 2010, 08:53:15 pm
content: Hello, that's called an audio spectrum analyzer. You can build one by sampling the audio signal and applying an FFT. Every frequency component can have an LED bar that shows its magnitude.

author: Zero999
author_rank: Super Contributor
timestamp: July 20, 2010, 11:09:09 pm
content: It's called a colour organ, you need three filters which each have different pass bands and a peek detector so the sensitivity shouldn't need to be adjusted because the music volume changes.

author: krd777
author_rank: Contributor
timestamp: July 21, 2010, 01:04:48 am
content: Quote from: Hero999 on July 20, 2010, 11:09:09 pmAh ah! Yes! I'm going to do it with UV LEDs, gives a nice effect with fluorescent tint as seen in the video! I've already done the filters in the schematics I attached. Will just decide tomorrow which frequencies I'll pick up in which of the LEDs. And it's true, I haven't used a peek detector! I'll search how it works and I'll add it before the OpAmp!Thanks for the idea Hero999!

author: Zero999
author_rank: Super Contributor
timestamp: July 21, 2010, 03:38:45 pm
content: Oh yes, I didn't look at your schematic properly, I missed the filters.Single pole filters probably won't be good enough for what you want, you might want a filter with a sharper cut-off.

author: krd777
author_rank: Contributor
timestamp: July 21, 2010, 10:20:35 pm
content: Quote from: Hero999 on July 21, 2010, 03:38:45 pmHey there Hero999!I thought so xDI've just done it and it is working properly but yes, sharper filters would be better. It is working right now but needed a bit of tweaking because it wasn't being consistent with the calculations I've done (the filter's cut-off frequencies I mean). I shall post the final schematic I have at the moment tomorrow, and then change the filters with better ones as you suggested!Won't post a video of it working right now because it's already late to turn the volume up xD But will do tomorrow. Also couldn't buy UV LEDSs because they sold out, so are only available in September. Will search for them in another city tomorrow too!

author: krd777
author_rank: Contributor
timestamp: August 05, 2010, 03:03:03 pm
content: Hi again everyone!Here is the video of the circuit working!

author: MTron
author_rank: Regular Contributor
timestamp: August 05, 2010, 04:49:43 pm
content: very cool!...you should amp up the design- use a couple more LED's and put it in a cool enclosure

author: Zero999
author_rank: Super Contributor
timestamp: August 05, 2010, 06:02:16 pm
content: Good, you got it working.The video could be better though, the camera isn't on the LEDs half of the time.I think it would look better if the LEDs were different colours and I agree that more LEDs would be good too.

author: Simon
author_rank: Unknown
timestamp: August 05, 2010, 06:13:25 pm
content: I think you need to make each channel less sensitive so that it flashes a bit more,Hero: I think he was trying to show the leds on the ceiling where they had more effect and were seperated more

author: krd777
author_rank: Contributor
timestamp: August 05, 2010, 06:42:26 pm
content: Ah! I'm sorry! Camera isn't very good.. :SQuoteYes! It will have UV LED's and a friend of mine wants to do a design for it with fluorescent liquids of different colours too, like the video we saw first on youtube.Another idea of another friend is to hack his speakers with bigger lights.Quoteeheh, sorry for the lack of cameraman skills Hero999 xDI was trying to show the light in the room, but the camera doesn't capture half of it. sorry about that.Different colours for sure! At least we're thinking first UV LEDS and coloured fluorescent fluids.Also, yes, more LEDS! That's the reason I'm using IRFZ44N Mosfets, so I can put more LEDS and probably a bigger power source.QuoteYes, you're right Simon! I need to have better filters, since I'm using single pole ones, which means a dull cut off. It's the next step for it.Also it's lacking the band pass filter at the moment.And yes, was trying to show the lights in the ceiling, but the camera captures it way too dark.Thank you very much for the input everyone !I shall be back with better filters. And around September, it will be applied to my friends design probably.P.S.: I haven't done a peek detector yet as Hero999 recommended before, but I haven't forgot the idea!

author: Zero999
author_rank: Super Contributor
timestamp: August 05, 2010, 10:04:27 pm
content: Anothing thing I've noticed is that the MOSFETs are set up as source followers which drop a lot of voltage so you're probably not getting as higher LED current as you think. This ciertainly isn't a problem with one LED per channel but I suspect it could be more of an issue at higher currents.

author: krd777
author_rank: Contributor
timestamp: August 05, 2010, 11:06:41 pm
content: Quote from: Hero999 on August 05, 2010, 10:04:27 pmSorry, didn't get the source follower. You mean I shouldn't be using the same source I'm using for the OpAmp? Or is it the way the Mosfets are connected? I thought controlling the gate with that audio to let the LEDS light up was the correct implementation, is there any other way?P.S.: I shall update the schematic since I'm now using a different OpAmp for each filter and I'm also filtering first, then amplifying after, and then send that signal to Mosfets's gates. But the idea and principle is still the same.