Audio switch for camaro

[zathrasb5]

So, I have picked back up a project that I started on a few years ago.  I have a 1986 Camaro, and want upgrade the radio by adding bluetooth

The normal way of doing this to these radios is to splice into the Audio lines from the radio to the amp, and instructions are easy to find from the Camaro guys.  A switching headphones jack is added in; when a plug is inserted, you get the AUX, when it is removed, you get the radio. 

I want to go one step further and add Bluetooth, so I need an audio switch, as opposed to a physical switch.

A got a wet sounds Bluetooth adaptor, which handles all the Bluetooth and audio.  It has an Audio out, an AUX in in, and an "on" line to indicate when it is turned on.

The car also has an power antenna which I would like to switch off when the Bluetooth is on.

I plan on fitting everything into the ashtray, so board space is an issue.  I had originally planed to ad a USB power port, but there is no way I can squeeze that in.

Here is what I have so far:
1)  An 8V linear regulator, with a zenior diode and polyfuses,
2)  A high pass filter and voltage bias to bring the line up to 4V,
3)  A Max 4053 switch,
4)  A MOFET to switch the 4053 from the signal from the wet sounds,
5)  A MOFET to switch on a LED from the signal from the wet sounds,
6)  A MOFET to switch the relay in the car for the power antenna (off if the Wet sounds is on).  (I have a flyback diode here due to the relay.

Am I on the right track? 
Have I seriously messed up anything that is going to let all the magic smoke out? 
Is there I way I can make the design better, or reduce my board space?

[Renate]

If you are running the 4053 on 8V then your logic levels have to be commensurate.
Low is less than ~ 2.5V, High is greater than ~ 5.5V.
(Extrapolated from data sheet on 10V, 3.5 V, 7 V)

[zathrasb5]

Thanks;  The datasheet for the max4053 has the high as 2.4V, so i have a voltage divider R6, R8, giving 3.2V (30% more).  It should be 0V when low.


I can't see in the datasheet where that changes based on the Vin?  Should I eliminate the voltage divider, and just run the 8v in?

[Renate]

No dividers.

[zathrasb5]

From the Max4053 datasheet.  It apepars to always switch at 0.8/2.4V

[Renate]

You're right, the MAX4053 is not like the industry CD4053B.
Deeper in the MAX datasheet they mention that the high threshold goes to 3.1 when using unipolar 12 V supply.
Still, you could swing the control inputs 0 V to 8 V.
It might make life easier if you blew the chip and replaced it with a CD4053B.

[zathrasb5]

Cool.  I just picked the Max chip at random; didn't know it wasn't standard.

I will eliminate the voltage divider.  I think I can also combine the mofet for the max 4053 and the led into one switch.

[Renate]

It might make life easier if you blew the chip and replaced it with a CD4053B.

(I meant that you should use the Max4053 now but if it blew up years from now a boring 4053 would work.
The Max4053 probably has better specs than the old stuff.)