LED Spectrum Analyzer schematics

In summary: VU meter.In summary, the individual LED lights in a car stereo should jump up and down to the music, giving the user a direct feed off of the head unit. There are many different circuits and schematics available on the internet that would meet this requirement, but the most complete option may be to purchase a pre-made circuit.
  • #1
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Hi,
I am looking to build a basic spectrum analyzer (if that is what you would call it) out of some LED lights for a car stereo.

Basically, I want about 8 - 10 bars (for different frequency bands), and I want them to jump up and down to the music, giving it a direct feed off of the car stereo head unit.

Looking for advice on components, any schematics that I may be able to use for the various parts (I figure I will need to build several cheap bandpass filters for each of the frequency bands, or use some sort of multi-band filter that I might find in a basic cheap equilizer circuit or something like that.

Still trying to get some ideas.
 
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  • #2
I googled stereo led bargraph, and got lots of great hits. Here's the 2nd one on the list:

http://www.talkingelectronics.com/Projects/StereoVUmeter/StereoVU.html [Broken]

Welcome to PF, Bob.
 
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  • #3
Thanks for the info (and the welcome)

I have already been doing a bit of searching...

These two most closely match the basis of what I am trying to accomplish:
http://sound.westhost.com/project60.htm
and most specifically this:
http://www.rose-hulman.edu/~sharpjm/led/led.html [Broken]

The second link, is almost exactly what I am trying to accomplish, however, I am relatively new to circuit design, and I was hoping to find something that was a bit more complete, but I don't think I'm going to .

The best I can tell, I am going to end up building 8-10 of the circuits that are described in the second link, and then I will need to build 6-8 bandpass filters , plus a high-pass filter and a low-pass filter and then feed my audio input into that whole mess.

Does anyone know of a circuit design that would give me multiple band bandpass filters all in one project, that I could use as a basis to feed into the LED circuits?
 
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  • #4
One alternative is to use Digital Signal Processing (DSP) and a fast microcontroller (uC) to process the audio and calculate the running filter output values. Have you explored the DSP approach at all?
 
  • #5
No, I haven't. I'm not sure if such a circuit would be beyond my capabilities or not...I guess it would depend on how much I had to start with...

How expensive or complex would it be to build such a circuit? Would I still be able to use the same basic LED VU meter design for the outputs?
 
  • #6
If you haven't programmed a uC before, and haven't had an introduction to DSP yet, then it probably is not a good match for your current project. If you were going to use the DSP option, then you would probably buy a medium-end uC evaluation board (like for a PIC18F4455 or Atmel AT91SAM7S64 or similar), and build an audio ADC circuit and an interface circuit to your LED drive board from the uC evaluation board. Then you'd program the DSP algorithm (mostly in assembly with a C wrapper) and test it out using the appropriate debugger.
 
  • #7
Yeah, probably true. I am more of a programmer than I am a circuit designer, but this might be a more abitious project than I would want to take on as a first time uC program.

I found this Velleman kit that I think is what I was looking for:
http://www.animeguru.com/images/velleman/k4300.html

However, from what I understand, one of the ICs is no longer available.

Still trying to figure out if there is a way around that, or to at least use this as a building block...
 
  • #9
Have you made any progress on this project?

I've been beating my head against the wall, trying to find a practical solution to the same issues you faced. Please let me know. I'm very interested!

Thanks a bunch.
 
  • #10
SilentBob said:
Yeah, probably true. I am more of a programmer than I am a circuit designer, but this might be a more abitious project than I would want to take on as a first time uC program.

I found this Velleman kit that I think is what I was looking for:
http://www.animeguru.com/images/velleman/k4300.html

However, from what I understand, one of the ICs is no longer available.

Still trying to figure out if there is a way around that, or to at least use this as a building block...
The key element to the Velleman circuit is the Filter Sections A and B which pick out the frequency bands for the display.
A DSP solution would implement these as a FFT in software.

With some minor modifications, you should be able to substitute the LM3914 for the obsolete IC
Or you could use the first circuit Berkeman posted as a substitute.
 
  • #11
No DSPs...

Hi...

Thanks for the reply. I am looking for a clean, simple elegant solution to the filter design for the different LED bars. The LM3914 is not scarce... I just bought a dozen off ebay for about $30. Using a DSP is not an option for me... and I know absolutely nothing about them. I'm not into saving pennies on transistors either. I'm just looking for suggestions on a simple filter design, maybe a modular design using standard/basic components that I can replicate and adjust the component values to filter the different frequency bands.

Does anyone have a simple solution that does NOT involve a DSP? I know there is one, because the old stereos had this before DSPs were availlable.

Many thanks
 
  • #12
Old stereos used high pass and low pass fillters.
Using this approach a 3 channel display can be done with only a few passive components.

For more channels you need active bandpass filters like the ones in the Velleman circuit.
All 10 filters are identical except for the component values.
They do not use DSP.
 

1. What is a LED Spectrum Analyzer schematic?

A LED Spectrum Analyzer schematic is a visual representation of the components and connections needed to build a device that measures and displays the spectrum of light emitted by LEDs. It includes detailed information about the circuit, such as the type of LEDs, resistors, capacitors, and other electronic components needed for the device to function.

2. How does a LED Spectrum Analyzer work?

A LED Spectrum Analyzer works by using a photodiode or phototransistor to detect the light emitted by an LED. The light is then converted into an electrical signal, which is amplified and analyzed by a microcontroller or other electronic components. The resulting spectrum is displayed on a screen or LED bar graph, allowing for visual analysis of the LED's spectral output.

3. What are the benefits of using a LED Spectrum Analyzer?

A LED Spectrum Analyzer can be a useful tool for scientists, engineers, and hobbyists who are working with LEDs. It allows for accurate measurement and analysis of the spectral output of LED lights, which can help in the design and optimization of LED lighting systems. It can also be used to identify faulty or defective LEDs, ensuring the quality and reliability of LED products.

4. Are there different types of LED Spectrum Analyzer schematics?

Yes, there are various types of LED Spectrum Analyzer schematics, depending on the specific application and requirements. Some schematics may use a single LED and photodiode for simple measurements, while others may use multiple LEDs and sensors for more complex analysis. Additionally, the components and circuitry used may vary depending on whether the analyzer is designed for visible light or other spectrums, such as UV or IR.

5. Can I build a LED Spectrum Analyzer myself?

Yes, it is possible to build a LED Spectrum Analyzer using a schematic and the necessary components. However, it may require a good understanding of electronics and circuitry, as well as access to specific tools and equipment. Alternatively, there are also pre-built LED Spectrum Analyzers available for purchase that may be more suitable for those without technical expertise.

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