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Music to led opinion

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396sahara

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So i will accept all flames since this is my first post. Got a little project me and my eight year old are working on. Wanting to build a circuit to take the line out voltage from a phone or ipod and through a splitter, play music to her radio while having 4 led ouputs, left and right channels whilst each channel is divided into two filtered outputs for bass and highs( these will drive seperate led strips) . We are going to preassemle on my breadboard so here is where i am at on this so far:

1. Wanting to utilize the 12 volt led strips that are premade (https://www.superbrightleds.com/mor...power-led-flexible-light-strip--nfls-x3/1465/)
2. I already have some 741's and some 386's as well as tip31 and 120's. ( this can be changed)
3. I was thinking that from the output we could run into dual 741's (left and right channel) to amplify the output to around 1.5 volts max then into a potentiometer to adjust sensitivity.
4. following the 741's i could run the output into dual tip31's then to dual the lm386'ssetup one for an RC high pass and RC low pass.
5. basically each channel (left and right stereo) would have one 741 to boost the output the the tips 31 that i can adjust the voltage prior to input to avoid the saturation point of the tip31 and into the 386's to meet the 12vdc requirement of the led stip while allowing me to create a simple RC filter for high/low.

I am not entirely sure of the output current draw of the led strips, have a feeling this is a limiting factor.
I am open to ( that is a ridiculous idea). I haven't been in this game so this is just using the Google FOO. If it pleases the audience i would appreciate any ideas to simplify this idea, Would really like to be able to run this off a 12vdc power source that i already have available.
 
Your first reply - no flames, welcome to the forum.

Not precisely what you are looking for but heres a really simple circuit that does that and doesnt use ic's at all, see post #2.

Depending what current your strips pull you might need to use larger led output transistors, the pnp complement to the tip120 darlingtons might do the job if you put 2 d1's in series to ground.

https://electronics.stackexchange.c...es-and-fades-color-leds-synchronized-to-music
 
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Thank you for the reply! appreciate the lack of flame :) I like the color organ design to play with with the dome LED's i have. I am actually interested in sudo complex for the circuit to let my kiddo kinda see what can be done with a bunch of alien looking components ( while i learn myself ). I just really wasn't sure if maybe a comparator type circuit or something with less actual components would do the trick. i would like the adjust ability so it can be played with.
 
Why use LM386 power amplifiers? With a 12V supply then their output swing is only 6.5V p-p into 8 ohms which is a voltage swing much too low for the LED strips. Also an LM386 makes a lousy filter.
A 741 opamp can be a preamp and another 741 can be a filter. Rectify the output to drive a low loss Mosfet.
The TIP31 does not have high enough gain and the TIP120 has lots of gain but has too much voltage loss.

If you want to have the loudness change the brightness then linear will not work because our vision's sensitivity to brightness is not linear, it is logarithmic. You do not want the complication of logarithmic converters. The Mosfets will simply switch on and off. Let the duty-cycle of the music vary the brightness.
 
OK I understand now.
You could just filter bass mid and high using a simple tone control circuit and feed the individual outputs to seperate lm386's and drive the leds with audio, not sure how good that would be, you could try feeding a single led string directly with audio and see how it looks.
Filters, amplifiers, comparators an one shot circuits all combined will get kinda complex and tricky to get working.
 
An LM386 is an audio power amplifier designed to drive a speaker. Its voltage losses are much too high to turn on LED strips.
 
Thank you for the reply AudioGuru, as funny as it may sound, your the reason why i am chasing this darn idea! I found an old 2009 post some time ago via google and got me to thinking.

I will use the 741's like you said , one for preamp and a second to filter the seperate freq. Would any little P-mosfet work that has the right vdc/current?
 
A lousy old 741 opamp with a 12V supply might have a maximum output swing of only 6V peak-to-peak which is only 3V peak into a rectifier then its output is only 2.3V peak which is too low to turn on a Mosfet. Many modern opamps will have an 11V or 12V p-p output swing to turn on ANY Mosfet with a nice big voltage.
 
Any good part numbers come to mind regarding the modern op amp? And just so i understand where we are now.

1. Line out from music source around 1 volt into a 741 (preamp) for each channel
2. that will drive the voltage up into a modern op amp to reach my required 12vdc
3. Should be able to filter the modern op amp using a RC filter
4. Allow the 12vdc modern opamp output to switch the mosfet.
5. As the intial output voltage changes to the music from the line out, this will drive through the preamp/opamp to the mosfet which will be set to switch at a determined voltage of roughly 9vdc? ( this is the low side for the strips to turn on)
6. The fluctuation is line out voltage should create the effect im shooting for by driving the brightness to the music
 
Most modern opamps come in tiny surface-mount packages today for soldering by robots. I have a stash of modern opamps in the standard easy-to-solder larger package. I do not know some that are modern but are in the old package. Maybe somebody else can recommend one.

The gain of the circuit driving the Mosfet will be high enough so that most of the music turns it on completely giving 12V to the LED strips. the duty-cycle of the music will have 12V peaks but the off-time varies the amount of brightness of the LEDs.
 
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