Will this circuit work?

[arthur106]

Please keep in mind that I have absolutely no experience with building or designing circuits.
I'm trying to get LED's to light up in sync with some music (The louder the music is, the brighter the LED's will glow). To do this, I am utilizing unused RCA audio outputs from my car's stereo system (I am not hooking this up to the speaker because that would required removing the door panel, and I know I would break something in the process. I will hook up two buttons on the dashboard to control the system (The first button will toggle the lights from red to blue to green to off. The second will switch it from a mode in which they light up in coordination with the music [powered by voltage created by RCA cable] to one in which they will shine a steady brightness [powered by 12V car battery]).
I have designed a circuit diagram that I believe will work. Could you please review it and tell me if I am doing anything wrong? Also, how could I make this better/simpler?
Thanks in advance!
Circuit Diagram: https://picturepush.com/public/7998516

 

[RetroTechie]

Welcome on the forum, arthur106! :-D

Also, how could I make this better/simpler?

1. Look up LM3914 / LM3915 datasheets. ICs specifically designed for this purpose, should cut down a lot on required external components.
2. That capacitor next to bridge rectifier would need a discharging resistor across it, otherwise it would just charge up to peak level & sit there. RC time in order of say, 0.1sec? Better: active rectification.
3. How do circuit ground & 0V point of the audio input relate to each other? You might want to AC-couple the input, and perhaps load it with a dummy load of some kind (what's supposed to be on there?).
4. Ditch those many diodes on the circuit power lines (blue). For reverse polarity protection, 1 diode for the circuit will do.
5. If voltage levels on the audio input are sufficient (read: if meant to power speakers), an even simpler method might be to power the LEDs directly with that. Appropriate sized resistors & perhaps a few zener diodes in series.

 

[BradtheRad]

Your concept could be workable after you do some testing and troubleshooting.

Following are items that need attention.

* The diode bridge has a volt threshold of 1.2V. The audio signal must exceed that level if it is to get through at all. At low volumes it will not get through.

* Pull-down resistors should be attached to the Clock pins of the 4017's. A value between 10K and 1 meg is suitable.

* Both of the 4017's ground pin and clock enable pin should be connected directly to each other. This makes 4 pins that can be connected. You can keep one diode between vehicle ground and the circuit board. (Typically the diode is installed between vehicle positive supply and the circuit board.)

* The output pins of the 4017's need a current path to ground. It may or may not be adequate to use the ground wire of the RCA leads. The diode intervenes.

* Output current from IC 2 pins is able to go into bias terminals of NPN transistors, and down through the LED's. This will light the LED regardless what is happening at IC 1. Reconfiguration of the transistors will be necessary.

Good luck. You show potential.