Care to design me a circuit ?


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Pablo

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Sep 1, 2004
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Blue/Green Planet
#1
Hi all,

I have a stereo (RCA) input to my car stereo. I want to input an MP3 player and a GPS into it.

Rather than just use a 2 channel mixer, I want one input to mute (adjustable) the other input when a signal is present.

By this I mean, listen to the MP3 music but when the GPS says,"turn right" I want the GPS voice to mute the MP3 music.

Does anyone out there have a circuit design for this "using discrete components" ?

I have not been into circuit design since the days of the "BC" transistors and would most likely guess some latest FETS would be good to use.

So, would anyone care to share a circuit design ???

Cheers and thanks :)
 

Del_CtrlnoAlt

Senior Member
Feb 15, 2003
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Outside the Dry Box.
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#4
Hi,

65 viewers but no one into circuit design :cry:

Oh well.......

its too sophisticated already, the circuit may cost a bomb... cos what i see, you need to have dual signal, yet 1 signal will cut off another if visible, mean you have to have a repeater & signal sensor or something to detect and reroute, from external, look like 2 source 1 output design...
 

yanyewkay

Senior Member
Sep 22, 2004
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Cons digger.
#5
not verified circuit. No values and no component number.. cos I'm lazy to calculate them.


the theory is that the incoming signal will trigger the mosfet to activate the relay. making use of the warning beep that most GPS will give prior to instructions, it will charge up the cap, also you wun get a fluctuating triggering of on/off/on/off. When the cap is sufficiently charged, the mosfet acts as a switch to turn on the relay (current from D to S flows).

When there is no signal, the relay with output connected to the NC to the MP3 player will supply the music to your HU. WHen the gps signal comes in, it switches the relay over.

You have to take note of the relay coil's back emf during the discharge as it might kill the fet. Didn't add that into the diagram cos it was drawn with paint and it's a pain to draw with that.

You might also want to add a buffer to the GPS inputs just before the cap (after the branch to the relay),so that the signal doesn't get distorted when it reach the HU.

Goodluck, give us the updated design once you complete modifying my circuit above. thanks!
 

wind30

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Mar 14, 2004
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#6
Hi,

65 viewers but no one into circuit design :cry:

Oh well.......
I design circuits for a living.... but I never use discrete components..... all on chip....

You probably need a analog multiplexer and a comparator to sense the GPS output and set the input of the multiplexer. Probably need a reference voltage + maybe 10 transistors?
 

Pablo

Senior Member
Sep 1, 2004
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#7
Hi all,

Thank you for the replies,

I have been away from electronics for toooo many years as you may see from the rough circuit idea.

A relay may cause too much of a thump in sound I think yanyewkay, but thank you for your input.

This is something like what I imagine would be a starting point (the same mirrored for the other channel).

Just looking at it now, I think there would need be a capacitor on the FET input to ground to clamp the mute :dunno:




Any ideas ?

Thank you again for your replies :)
 

yanyewkay

Senior Member
Sep 22, 2004
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Cons digger.
#8
I design circuits for a living.... but I never use discrete components..... all on chip....

You probably need a analog multiplexer and a comparator to sense the GPS output and set the input of the multiplexer. Probably need a reference voltage + maybe 10 transistors?
yups.. designing electronics have never been easier these days with all the SIP (system in package) chips. want wifi, bluetooth or gps? just drop in the chip can already. yes also my circuit can use an analog multiplexer to replace the relay, but you'll need one that accepts audio inputs. typically the kind of make before break types.
 

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