Audio Switching

S

smokelight101

Member
Hey everyone,
I have finally got my first car but it has a stock radio. There is no port for any type of audio input but i have found an old fm modulator. This allows me to finally pump some mp3s in to it :). But only one source can be connect at a time so I plan to build an audio switcher. I know that the project will require filtering and will be fused so don't worry, I have my padre helping. But I was wondering if you guys could recommend what you believe to be the best way to switch the audio. I was thinking a analog multiplexer? or maybe even relay. But believe relays would leave a large click every time audio is switched, maybe even hurt the speakers.

Thanks ,
Tyler Berezowsky
 
premelec

premelec

Senior Member
Rotary switch?

Unless you have a need to get complicated a rotary switch with many inputs and one output [to FM modulator] should work fine... have fun.........
 
B

BeanieBots

Moderator
Agree with Premelec.
Also, be it switch, relay or electronic, there will be a 'click' unless you do something to prevent it.
 
Buzby

Buzby

Senior Member
Hi,

Switching analogue (analog) signals from various sources will always give a 'click', unless you match the signal levels at the instant of switchover.

Something like :

http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010484

and

http://ww1.microchip.com/downloads/en/DeviceDoc/21117a.pdf

might be a solution.

Basically its a digitally controlled multiplexer with programmable gain.

Use the PICaxe to ramp the gain to zero, then select a new input, then ramp the gain up again.

You can do this in less than 0.1 Seconds, and no 'click' .

There are plenty other devices like this, do a bit of Googling for things like 'programmable gain' or 'VCA' ( voltage controlled amplifier )


Good Luck !
 
Buzby

Buzby

Senior Member
I've just thought of some more goodies you could programme into your PICaxe to give your 'stock' radio some bling.

How about a microphone into the ADC to give a value related to road noise, then ramp the volume accordingly.

Or feed your mobile phone audio into another input, and make your own hands-free.

Use a speech synth and lots of sensors to provide audio descriptions of errors in your motor, with a polite voice interrrupting your mp3 to announce them.

What else can we think of ?
 
S

smokelight101

Member
Sweet, Thanks you gys for all the help. There is a digonistic port right under my radio so i was deffnialy thinking about that. I plan to use a encoder knob i pulled off an old XM radio to change the channels that will be hooked upto a picaxe than to the multeplexer with adjustable gain.

If you guys got any more ideas for "bling" that be awsome

Thanks,
Tyler
 
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