need help: 3.5mm jack w/ a micro switch?

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i'm putting a wired fm modulator in my car; it's the way i want to run
my mp3 player into the existing radio. the modulator has a 3.5mm phono
jack for the mp3 player to hook into, with the thing powered by the car
battery (i'm going to use the cig lighter). it also has an on off
switch. But what i would like to do, if possible, is have it so that
the modulator is turned on when i hook up the mp3 player to the phono
jack and is turned off when i remove the mp3 player from the jack. i'm
thinking maybe there's some combination of 3.5mm jack and micro switch.
or could i make something like that?

if so perhaps someone could tell me what part(s) to get at radio shack
and how to put the thing together.

thanks!

 

[Ross Herbert]

i'm putting a wired fm modulator in my car; it's the way i want to run
my mp3 player into the existing radio. the modulator has a 3.5mm phono
jack for the mp3 player to hook into, with the thing powered by the car
battery (i'm going to use the cig lighter). it also has an on off
switch. But what i would like to do, if possible, is have it so that
the modulator is turned on when i hook up the mp3 player to the phono
jack and is turned off when i remove the mp3 player from the jack. i'm
thinking maybe there's some combination of 3.5mm jack and micro switch.
or could i make something like that?

if so perhaps someone could tell me what part(s) to get at radio shack
and how to put the thing together.

thanks!

What you are looking for is a jack with an auxiliary contact isolated
from the signal connections. I'm sorry, but this item does not exist.
3.5mm jacks currently available can have audio signal disconnect
contacts (if required), but not an additional isolated make contact.

Jacks which do have isolated contacts are used in telephone exchange
equipment areas and these are 1/4" (6.35mm) types.
See jack config. 'C'
http://www.answers.com/topic/jack-plug

At best, a 3.5mm jack will be arranged as in config. 'D'

 

[Lostgallifreyan]

What you are looking for is a jack with an auxiliary contact isolated
from the signal connections. I'm sorry, but this item does not exist.

Or a make contact (not break) on the ground wire. THose exist, and I've
even seen a separate aux switch on one 3.5 mm jack socket. You're right
about custom though. Very. As fitting one will almost certainly mean
adapting a case to take a socket that wouldn't otherwise fit, and as 3.5 mm
is a lousy standard anyway for reliability, why not rehouse the modulator
in a metal box and fit a quarter inch jack? That way you're more likely to
find a standard part with a switch on it, as well as get something that
will stand up to the kind of wear it's going to get in a car.

 

[Lostgallifreyan]

Important (damage prevention) followup!

When plugging the jack through the ground contacts, if you do use a make-
contact in the ground, even with a fused supply, there is a chance of the
12V supply dumping into the output of the MP3 player, so independent
switching is vital really. And if you have to rehouse, you're not limited
to jacks at all. >

Why not use a 5 pin Neutrik XLR? That would be pretty much bombproof, and
you could use the two extra pins in the socket for the positive supply
line, and short them in the plug. You might get by with the four-pin XLR
and use the screen as ground. I think miniature XLR's exist too.