LED Organ Help

[wolfgang959]

Hi ive been wanting to make an LED organ for a while now however there are not many schematics on the internet which are very useful because there is missing information and what not. So ive started to design my own and have been getting a bit of a headache over it.

I am designing it around using op amps however i believe you can also use transistors i don't know which gives better results. i have tried using Texas instruments filter pro software to try and get the resistor and capacitor values for use in a op-amp based active filter, but its really confusing and i haven't a clue on what to do.

i want to use 3 channels Treble, Mid and Bass so i would need to make a low pass, high pass and a band pass filters. However the thing that got me thinking was the filters would be set to say a certain Hz value like 100Hz, 900Hz and 3KHz (i found these values on one of the schematics) however the Hz ranges for bass, mid and treble are 20Hz - 200Hz, 200Hz - 4KHz and 4KHz - 20KHz. so i don't know what HZ value would be best for each one to achieve a good looking visual experience.

specification:
5 - 10 High powerd leds for each channel
12v DC 500mA power supply
audio jack in

thanks for any help i can get for this project

 

[davenn]

hi there
welcome to the forums

you are saying a LED organ ? never heard of one before. do you really mean a sound to light display ? sounds like it.

for audio stuff you wouldnt really need to worry about freq's below ~ 200 Hz or over 10 kHz. so with that range in mind break it into 3 sections. there will be some overlap between the filtered stages, thats to be expected unles you had very precise filtering.
Which isnt really needed in your project

cheers
Dave

 

[wolfgang959]

hi dave and yea basically a sound to light display so i can connect a audio jack into my alienware laptop because it has 2 speaker outputs saves me buying a splitter.

and sorry im a tad confused about what you mean with the freq's are you saying for bass i should have a filter which is set too 200Hz. Also how do i work out the resistor and capacitor values for each frequency i choose. and also what about the number of leds i can have for each section.

thanks
josh

 

[KJ6EAD]

You can get a single IC to do all the filtering and more. These have been used on lots of Arduino projects.
http://www.mix-sig.com/datasheets/MSGEQ7.pdf

 

[alfa88]

A Schematic

I was thinking of slapping one together myself. There's a schematic here:
http://blog.makezine.com/archive/2010/10/circuit-skills-led-color-organ-spon.html
If I'm not mistaken the question of color organs has been asked before on this forum. You might want to do a search here for other schemes.

 

[wolfgang959]

yea thats one ive seen too however the results have been varried from people who have followed that schematic and apparently some of the values are wrong and its difficult to understand what to change without an updated schematic posted.

however thanks to KJ6EAD for finding the MSGEQ7 chip which does pritty much everything for you (as stated in datasheet):

The seven band graphic equalizer IC is a CMOS chip
that divides the audio spectrum into seven bands,
63Hz, 160Hz, 400Hz, 1kHz, 2.5kHz, 6.25kHz and
16kHz. The seven frequencies are peak detected
and multiplexed to the output to provide a DC representation
of the amplitude of each band. No external
components are needed to select the filter responses.
Only an off chip resistor and capacitor are
needed to select the on chip clock oscillator frequency.
The filter center frequencies track this frequency.

 

[wolfgang959]

i also found another IC that can be used which may in fact be better than the MSGEQ7 because the MSGEQ7 is multiplexed so all the frequency's come out of one pin which makes it slightly more difficult for a true analoge application where the MSGEQ7 is good is if you want to use it with a digital device such as an Arduino board.

however im working on purely analogue so this chip the BA3812L seem like a good choice i would never have found this if it hadn't been the comment about the MSGEQ7. This chip has a higher voltage range which i was looking for (3.5V to 16V) and originally i was only going to use 3 frequency's but this chip has the ability to have 5 so gives me more options if i want to expand they can also be combined to make a 10 point single channel EQ (using 2 ICs) or a 7 point stereo channel EQ (3 ICs).

only trouble im going to have yet again is setting the frequency's but it allows me to cut down on alot of things and its also designed more for the purpose i need.

 

[KJ6EAD]

Rohm makes several bandpass filters. I researched them previously and if I remember correctly, at least one had an operational mode that didn't require a microcontroller.
http://www.rohm.com/products/lsi/sound/accessory/sel3.php#lineup

 

[wolfgang959]

cheers for that however im having trouble trying to get hold of the IC's however i found a schematic for a circuit made by xkits, which looks really good i the youtube videos they have shown of the product however researching the the schematic im having trouble understanding some parts of it when im making a pcb of it.

http://www.xkitz.com/catalog/documentation/XLO-5DC_Instr_Manual.pdf

also what software do you think is best for making circuits?

cheers