Audios following LED

[Peter_wadley]

Hey,

I couldnt find this in the search (since I dont really know what you call it)

Does anybody have any schematics?

https://www.youtube.com/watch?v=xl9Bu6F19BM&NR=1

 

[Peter_wadley]

Okk ive made one that works ok

Used a 741 op-amp (non inverting setup)

This is AMAZING!! It looks soo neat!

I think i just fell in love with analog!!!

Now that i think of it ive never made an analog circuit

Is there a way to make certain LEDs light up at certain frequencies?

I would love to learn such filtering

 

[iceblue]

You can use bandpass filters to filter the relevant frequencies to each individual led. That way you could have a green one for low frequency, blue for mid, red for high, etc. If you went for just low, mid and high frequencies you would need a low pass for the low (bass) freq, bandpass for the mid, and high pass for the high (treble) frequencies. Bandpass filters allow a certain range (BAND) of frequencies to PASS. High pass and low pass, as the names suggest, allow high and low frequencies (respectively) to pass through, blocking off all the others.

Do a search. Theres plenty of topics discussing this. Sure you will find the answers you need there.

 

[kchriste]

Google for "color organ"
You could adapt this one for LEDs by eliminating the power FETs and putting the LEDs in series with the resistors on the collectors of the 2n3904s:
**broken link removed**
Note: The 1uf caps on the output of the OpAmps appear to be backwards. The input OpAmp isn't biased right and isn't really needed anyway. Something like this:

 

[Brian Hoskins]

If you're a PIC man, and you're also interested in analog Electronics, I know the PERFECT project for you - check this out.

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

Brian

 

[Peter_wadley]

Hey those are great project!

I went out this morning and bought the LM3915

It really is a great chip as im sure you all know!

I think my first analog class is in my second year .. I am in the 1B term right now..

I cant wait to get through these basic science and math classes so i can dive right into all that the ECE department has!!

Right now I basically have the sound from my computer entering a non inverting lm 358 op amp.. with 2x gain.. the signal goes into the 3915 (logarithmic) chip and outputs the VU on red LEDs..

The lower numbered lights were dimming once the upper lights were active.. so added a 100uf decoupling cap.. fixed it..

Here a few questions:

I cant figure out how to take the small signal output by the computer without degrading the quality of the speakers..

I have the signal split..

I think Im going to make 2 (10 LED) meters .. once for the left channel and one for the right.. probably tape them to my monitor

Id like to use red LEDS for the lower sound levels, then yellow and at the top green..

Im just wondering if different colored LEDS require different current inorder to look the same brightness

I hope im not asking to many questions/ starting to many new threads.. its just that I am on my COOP term for my program and able to finally attack all the projects I couldnt do while in residence!

thanks

 

[Peter_wadley]

Forgot to mention

When I tie pin 9 to pin 11 of the 3915.. it doesnt enter dot mode.. it stays in bar mode with a decrease in LED brightness hmm

 

[audioguru]

Forgot to mention

When I tie pin 9 to pin 11 of the 3915.. it doesnt enter dot mode.. it stays in bar mode with a decrease in LED brightness hmm

Look again at the datasheet.
If pin 9 is connected to the positive supply the IC is in the bar mode.
When pin 9 is open then it is in the dot mode.

The dot mode is just a dim blur unless you use one of the peak detector circuits shown in the datasheet so the brightest LED lights long enough for you to see it. The circuit with the low, medium and high frequency bandpass filters also has peak detectors using the dides and capacitors.