Laptop to car speakers curcuit board

[PaulD]

Hello all,
I took electronics in ’89, but I still remember a lot, and still know how to solder. That being said, what I want to do is build a cheap circuit board for my car. The purpose is so that I play audio from my laptop over my car stereo speakers. What I imagine as the final product is a stereo cable from my laptop to a stereo connector on a circuit board. From there I will need to amplify the signal to play over the car stereo speakers. I will control the output with my laptop. My speakers are stock so I only need 4 to 8 watts. I plan to splice all the speaker wires coming out from my car stereo, and soldering them to the circuit board. From there, there will be some kind of auto-switch that will automatically switch to my laptop input when a signal is detected, and then switch back to car stereo when signal is absent. Cool huh. This sounds like it will be a lot of fun, and hope it won’t set me back any further than about $20. Your help will be greatly appreciated. Thanks.

Paul

BTW, there is a crude drawing here:
**broken link removed**
No laughing, I’m a computer geek, not a EE.

 

[Exo]

Well, a nice little +- 8 watt amplifier can be made using a TDA2003. It's meant for car audio purposes, so it can be ran of 12V directly.

here's the datasheet for it
https://www.electro-tech-online.com/custompdfs/2004/07/tda2003.pdf
There is a working scematic in the datasheet on the bottom of page 1.

You'll need to make 2 of 'em, for stereo (or 4 if your car has 4 speakers).
You can use the headphone output on your laptop as input for the amps.

The simplest way to switch the signal is probabely by using a couple of relays. Don't forget to switch of the power of the tda2003 amps if you're listening to the radio (or they'll just be wasting power)...

As for a signal detecting (for auto switching), I have a scematic for such a thing lying around somewhere, I'll see if i can find it.

 

[PaulD]

Thanks EXO, you’re awesome. I'll look for that signal sensing schematic when you find it. In the mean time, I'll work on this amp. Thanks again.

 

[Exo]

Here's the scematic for the audio signal detector. It outputs a voltage around 2.5Volts when an audio signal is applied...

You'll need some logic circuitry to make this work. If there is a pause in the audio (a silent moment) then it will see this as 'no signal' and the output will be gone.