Detect that headphones have been plugged in

[radexito]

Hello I am working on a little project (Sound Switch) and i need a way to detect that i have plugged in a headphone jack.

I've looked on the net and people suggested that you could measure resistance on the jack or buy the more expensive jack with a mechanical switch, if i would want to go for the cheaper option (resistance) what would i need to test the resistance and if headphones are detected switch my relay


Sorry if its hard to understand.
Thanks Radexito

[olsenn]

There's no need for active circuitry in something like this; just about all 3.5mm headphone jacks (including the cheaper ones) have an extra terminal that breaks contact with the ground plate when you physically connect your headphones.

[radexito]

Oh, thanks I did not know that
you learn something new everyday

EDIT
Also will it be safe to run 12v through that?

[Rerouter]

a jack with a detection switch is expensive? comapared to a non switched since when?

if you really want to go ahead with this pursuit http://www.eetkorea.com/STATIC/PDF/200903/EEKOL_2009MAR24_POW_NT_88.pdf

but in all seriousness i can not see how the switch option will cost any significant figure more than what it takes to switch under a certain resistance, as i am probably right to assume your signal is center biased rather than DC biased,

[Rerouter]

yes you can run 12V through it easily just not more than say half an amp per terminal absolute max,

[radexito]

I've read that those with the switches go for 6 bucks...
maybe it was very old article.

At the moment my circuit looks like

and I am going to add more stuff into it soon(more channels(3 in 3 out)), and i want to mute all channels when headphones are plugged in

[olsenn]

Hell no; don't waste your time with resistors and diodes. Check out the headphone socket at the bottom of this page: http://futurlec.com/Audio-Miniature.shtml (part number: P035SCK03

It is a standard layout 5-pin switched socket, and they cost $0.40/each. I've seen them go for as little as 10 cents a piece if you order in bulk.

[radexito]

Do you know if there is a non PCB mounted version?
my design is something like this:

[Rerouter]

edit:
http://www.digikey.com.au/product-detail/en/SJ1-3514/CP1-3514-ND/738682

[olsenn]

Do you know if there is a non PCB mounted version?

Of course you can solder leads onto any part, but I'm sure you can get cheaper parts than the one from element14. If your device is going to be bulky and in a professionalk enclosure etc. you may even wish to go for a 6.5mm socket (you can get adapters for your headphones) or even an XLR... this will be more durable.

I'd recommend checking various sites for switched 3.5mm sockets and chosing the one that appeals most to you (with all things considered). Most of these sockets will have a little nut and washer to seal it sturdily to your enclosure.

[T4P]

Pretty much every socket i bought is switched 

Resistance measuring?