Building a car stereo system -- LED question

[fiveleaf]

Hey guys!

I found some great threads earlier, but would like to ask about a LED setup for my car stereo that I have in mind. Sound Quality is of utmost importance to me, and I am not willing to jeperdize it by splicing into any of the signal outputs that will end up at the speakers/sub.

That said, I do not have rear speakers installed. This leaves me with two "clean" outputs that would go to rear speakers... but instead will power my LED lighting system.

I have never worked with LEDs before. I would appreciate any advise you can give me on this install. I was thinking that I could send the rear outputs directly to an amp (or coil?) to first amplify the signal to above the operating power of the LEDs.
I would then splice the amp's output into three seperate, identical, signals. These would pass into a hi-pass (tweeter), band-pass (midrange), and low-pass (base) filters.
Each filtered signal then needs to get to it's respective color of LED. I assume that I need a resistor, which would vary depending on the number of LEDs I end up using.

The overall effect, if it can be pictured, should be quite interesting.

I'm wondering:
-->What should I use to amplify the signal? A car stereo amplifier comes to mind, but I'm thinking there might be a cheaper alternative...
-->The output of an amplifier is in both (+) and (-). I know that not connecting them may cause damage to the amplifier over extended periods of use. Any thoughts as to wheather this setup could damage the amp?
-->I'm used to working with car audio, and adjustible band-pass filters are usually precise and expensive. Is there something else I could use in it's place?
-->I recognize that I will need to install a resistor of sorts, before connecting the (+) amplified output to the LEDs. Do I just multiply the [Volts required by one LED] X [the number LEDs] = [Required Power]. I then take [.33]x[Power of amp]=[Power Availbiale].
[Power avabiale] - [Required Power] = [Resistance required in Amps] (Same for Volts?)

-->Sources for inexpensive LED (flexible) strips that can be stealthily installed? I don't want them to show in the daytime.
--> I know that these LED strips are usually expensive. I am willing to make my own. I am supposed to just wire them in parallel and make sure the (+) leads are insulated right up to the tip? If so, I could just buy 200 of each color and be on my merry way.

Remember, we're on a standard DC car battery here!

**broken link removed**

 

[Hero999]

I'd suggest different frequencies.

Bass <300Hz
Mid range 300Hz to 5kHz
Treble >5kHz.

The filters can be made from cheap resistors, capacitors and op-amps.

LEDs need a series resistor to limit the current, but as they're not going to be illuminated continuously, you can overdrive them slightly without anything bad happening.

What you're looking for is a colour organ, there are plenty of schematics on the Internet.

 

[Mike odom]

yes, standard color organ.

First, Speakers use way more power than LEDs. Unless, of course, you are hooking up 50 of them!

I don't know where you got your "I then take [.33]x[Power of amp]=[Power Availbiale]" from. Your stereo amp will be rated in max wattage, but it will also be rated at watts per channel. Just because you are using three channels doesn't mean each channel gets 1/3 the power. The front and rear speakers could be rated the same, or maybe the rear is rated higher to driver larger speakers.

Also, some stereos won't work with just the left or right speaker hooked up. Some need to see both before it drives that channel (Sony).

Although it's not apparent, you can figure out what voltage your speakers are being driven at. P= IE, but also I squared R (since E=IR) and P= E * E / R. Therefore, voltage = the square root of {the channel power times the speaker resistance (8 or 4 ohms)}. I mention this as LEDs have a minimum voltage to turn on. It is also not a good idea to parallel LEDs as they have different turn on voltages, so they won't share the current evenly.

 

[Hero999]

If you're going to connect the LEDs to the speaker outputs (which wouldn't recommend) then you need to include a diode in reverse parallel or a bridge rectifier to prevent the reverse voltage from being exceeded, as well as the mandatory series resistor.

 

[fiveleaf]

Your stereo amp will be rated in max wattage, but it will also be rated at watts per channel.

I would be using a mono amp.

I'm actually not sure if a stereo amp is the right choice; I figure I need something that provides me with a higher voltage to illuminate all these LEDs.
Yes, I plan on using hundreds of them


Hero, is there a choice besides using the stereo outputs?
Could I not just attach the (+) from the amp/coil and ground the rest of the LEDs to the chassis?
I can not do this with a regular audio amplifier, as it is a bad idea (and many will not work if) only the (+) terminal is used.

As far as the LEDs themselves go, I found three options...
WFLB series Waterproof Flexible Light Bar
FLB series Flexible Light Bar
or
SE-WFLS series Silicone Encased Waterproof Flexible Light Strips.

They are all basically 5 lumans per LED, with a beam pattern of 120-140 degrees. Some have the LEDs closer together than others, but that's about it. I have not been able to find any that are brighter, and will run on 9-14.8VDC.

I have to admit, I'm really aprehensive about making my own crossovers...

After doing a bunch of searching, It seems that there are 3 way color organs with amplifiers built in! This eliminates the need for both crossovers and a coil/amp! Most of them seem to rely on a microphone of some sort; I need one that will plug dirictly into the stereo, preferrably with RCA cables. I haven't found any that can operate on a normal car battery
I have found a couple that have both dimmers and a "light show" function though!

So after the organ, all I'm going to need are resistors?

I'll keep looking. Anyone else have experience in looking for these light organs for car audio use?

Edit: Though funds are limited, I don't mind spending $ on the right organ. Especially if it will cut out unnecessary wireing and make for a cleaner install. One that can be remote-mounted (doesn't have to be wireless) would be ideal, but I don't expect to find one.

 

[Hero999]

The LEDs you've linked to all have resistors built-in.

What's wrong with using a microphone? I was just about to suggest that.

Do you want to make it or are you happy to buy?

What about buying a colour organ and ruining it from an inverter? If so I think you'll need a pure sinewave inverter because the the triac triggering system probably won't be compatible with a modified sinewave.

The circuit I was going to suggest wouldn't be compatible with those LEDs because they have build in resistors and it relied on converting the audio signal to a varying current. I have another idea which uses PWM and should work with those LEDs.

 

[fiveleaf]

As far as the microphone goes, I saw it as adding unnecessary inaccuracy and wireing. Now that I think about it, I realize that it might actually reduce the ammount of wireing I need. That, and who really cares if it's going to be accurate. I guess mounting it behind/inside the dash would contribute to it.
I just don't want to have to remote-mount the microphone.


I have no problem buying the components.
I'm not familiar with PWM, could you possibly elaborate for me?

 

[Hero999]

PWM stands for Pulse Width Modulation, more information can be found on Wikipedia.

Yes accuracy isn't important, you only want to flash a few LEDs to the beat of the music, it's not like you want to be able demodulate the signal back to audio.

My original idea was to make the brightness of the LEDs proportional to the volume of the music which might be overkill. Just having the LEDs turn on when a certain volume threshold is exceeded might be good enough for what you want.

 

[fiveleaf]

Do you think I should be looking for LEDs without resistors built in?

 

[Hero999]

It doesn't matter, the circuit can be designed to work either way but you need to make that decision beforehand.

 

[fiveleaf]

I love watching my projects turn into overkill... What do I need to vary the intensity with the music? (I'm hoping for a sensitivity adjustor...)
I'll read up on it @ Wikipedia, and then to google to find one compatible with a car's battery...