Hi all,

This is probably a noob question, but I didn't know what to search for. Hopefully someone can help!

I have an old device that listens to sound, and lights up LEDs based on how loud the sound is. The output voltage of this device is 3v, USB powered.

I want to replace the stock LEDs with 5050 led strips, but they require 12v. I have a power pack to drive them, but I have no idea how to, or if it's possible to use the signal from the device, and use the 12v power from the power supply. Any thoughts?

I have basic/intermediate electronics knowledge, and I am very comfortable soldering.

Thanks so much in advance!

 

If you can access the LEDs then you could connect a transistor to that point to control the 12V LEDs.
How much current do the 5050 strips take?
But we need to know how the original LEDs are connected.
Do you have ready access to the circuit?

 

Hey there, thanks for responding!

I do have access to the circuit. The power supply I have is 12v, 2a, which is plenty to drive the 6 led strips.

 

 

I did some research on your transistor idea, and it seems like it would work! Any ideas on what type of transistor I would need?

Thanks agian for your help!

 

Okay.
What is the 3V output signal you were referring to.
Does it go from 3V to 0V when the LED is on and off?

 

Okay.
What is the 3V output signal you were referring to.
Does it go from 3V to 0V when the LED is on and off?

Sorry if I'm not being clear, or missing information. Thanks for your patience and support!

The unit that I want to modify provides up to 3v, depending how loud of a sound it hears. Ex: strong bass note plays, it will emit the full 3v, but will provide less power for softer notes.

After doing some research on a transistor, it looks like it is basically a switch; and now that I'm typing this, I'm starting to think a transistor might not work for the variable voltage I'm looking to achieve. :/

 

Are you sure your '3V' output is indeed that, rather than a PWM signal with a 3V 'average'? Did you measure the voltage with a DMM?
A LED's brightness is determined by the current through it, so the usual brighness control method is PWM, not a smoothly varying voltage.

 

Are you sure your '3V' output is indeed that, rather than a PWM signal with a 3V 'average'? Did you measure the voltage with a DMM?
A LED's brightness is determined by the current through it, so the usual brighness control method is PWM, not a smoothly varying voltage.

Well that just went way over my head. Lol I have a multi meter - is it something I could measure with that?

 

The unit that I want to modify provides up to 3v, depending how loud of a sound it hears. Ex: strong bass note plays, it will emit the full 3v, but will provide less power for softer notes.

How do you know that if you didn't measure it? Can you post a link to the datasheet for the unit, or post its schematic?

 

Because I used a multimeter to measure the voltage. Peak is 3v.

I don't have the wiring diagram. if it can be done easily or not. If it's not worth my time, then I'll start another project.

Again, I only have basic knowledge on electronics. Enough to get into trouble. Im trying to learn, but some of this stuff goes beyond my understanding. If this is not the right place to ask questions about this type of project, my apologies.

Thanks.

 

You've come to the right place.
We ask all these questions because we need that info to generate a good solution to your requirement.
Is there any way you can get access to an oscilloscope?

 

I have an old device that listens to sound, and lights up LEDs based on how loud the sound is.

Is it the LED brightness or the number of LEDs lit which varies with the sound level?

 

I think you should use a "power" op amp.

The variable, up to 3 volt output, would be amplified by the opamp. The opamp itself would be powered by your 12 volt adapter.
Set the gain for approx. 4, and Bob's your uncle.

 

http://m.ti.com/product/opa548

Open the data sheet and you will find circuit examples and formula to calculate gain and for setting output current limits

Good up to 5 amps. This amplifier can be set for a gain of 4 and will drive 12 volt LED's with an exact copy of the output from your 3 volt LED driver. It won't matter if the original device uses PWM or not. The amp will simply copy it and output it as a 12 volt drive signal. You will need to mount it to a heatsink of somekind.