HELP: Electronics Components

[Aaron]

I know a few members are more serious electronics tinkerers than I am so I’m hoping you can help me out.

I’m after a 3.5mm stereo headphon socket that incorporates a switch. The switch needs to be isolated from the audio signal and basically make a connection between two pins.

It’s to ‘sense’ that a plug has been instered into the socket and activate a function rather than just switch off the audio input to another device. The one I picked up from Jaycar just now only does that – inserting the switch simply breaks a pass-through function of the L & R audio signals.

What I need to do is upon the insertion of the plug pull a logic input line to ground.
I swear I’ve seen these aroudn and indeed bought one about 10 years ago when I was playing around with electronics moreso.

Ideas, sources, partnumbers?

A.

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Site Owner Guy.

[PandaBear]

Also remember seeing some that do that back in the 70s (mic & headphone jacks?), but they’ve all come inside audio equipment… short of scavenging them out of vintage AV gear or finding OEM NOS spareparts, not quite sure where one would buy those things separately.

Used to be place called “All Electronic Components” in Latrobe St Melb, but can’t seem to find them in YellowPages anymore. Maybe uA might know what happened to they, they usually had some ancient esoteric stocks.

[Aaron]

To make matters worse I can buy one – from Ford (of all things) for $30….. Me thinking the 1-2$ I recall them costing is much more correct 😉

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Site Owner Guy.

[merc-blue]

hye guys.. speaking of components does ne 1 no were i can get some of the more obscure components .. im thinking a online supplyer

[trash]

Yes, most of the 3.5 circuits have an audio in and audio out fuction. When no plug is present the two lines are connected, when the plug is inserted then the output is either open circuit
or in some cases earthed to the common pin.

Depending on what your doing with your with your plug socket, there are other ways around the problem. Is it an audio application or something else ?
Depending on what exactly your using it for a few extra components and 5 minutes with the soldering iron will solve it.

You may find the exact socket your looking for at Wes components or Farnell. Wes can be a little difficult if your trying to buy retail,
but a company name often fixes that.

[ph2t]

Aaron, the only one’s I know of have been discussed in detail already, sorry about that. As to hardware with a seperate switch, hmmmm I dunno.

Try http://www.rs-components.com.au they might help.

Cheers,

ph2t.

[micro_Amps]

You just beat me to it ph2t, Ive had a flick through the RS-Comps catalog, (all 3 inches of it), only to find that they dont have anything with an extra contact switch.
Panda, All Electronic Components had some excellent old stock, the shop was a time capsule of gear. They closed down about 2 years ago and a lovely persian rug shop opened up there.
95% off this week only, as usual, of course.
:)uA

[Aaron]

Yeah trash it’s an audio application on the plug…But the detection of the plug is a logic operation (tie pin to ground).

I’m look for something dirt cheap to implement and happy to listen to any ideas 😉

Seperate switch is doable but packaging could be a pain.

A.

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Site Owner Guy.

[ph2t]

Got a schematic Aaron?

[Aaron]

Of what I need?

Or what I’m interfacing?

In short what I’m infacings is a inptu into a Car stereo. There’s a ‘sense’ line that needs to be pulled to ground to enable the headunit to give the suer the option of selecting ‘AUX’ on the controls. If the pin is not grounded the user can’t select AUX.

I’m going to experience with setting the pic to ground permanently when the cable is connected and see if that affects operation 9ie will it force it to always start on AUX….Or if it will start on the selected mode.

A.

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Site Owner Guy.

[PandaBear]

Methinks Aaron has discovered its hard to put
3rd party headunits into a BArra.. :blush:

[Aaron]

Actually it’s to add an additional input to the stock system (I coughed up for the Premium sound so there’s no drama with quality). Me got a longer term plan of DVD type playback through the factory fitted 7″ TFT 😉

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Site Owner Guy.

[jamiekulhanek]

Pitty you arent gonna modd it 🙁

I have heard Rumours that HKS is going to develop an XR6 lineup of go fast bits.

[Aaron]

*laughs* HKS = Overpriced

So far the ‘known’ things are:

280-290Kw for $1200-1500 (ECU/Computer tuning)
290-330Kw for $1500 (Fuel pump, Injectors, oil cooler)

etc etc…

Depends on who’s gear 😉

But I’m sticking to mainly electronic whacky stuff 😉

A.

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Site Owner Guy.

[trash]

Ok Aaron,
it’s still a little vauge to me why you’re tinkering with something which seems to be inside the stereo where you don’t need to get to it.
But dealing directly with the problem…
the answer is simple. If the pin is connected to the audio line when the socket isn’t in use, then you need to deal with it. With your multimeter, measure the resistance/impedence between the audio and ground. There should be something there less than 10Kohms (high impedence).
If this is the case then you need to test the pin to make sure it goes open circuit when the plug is inserted. (>1 Megaohm)

To the sense pin you solder a choke. A big one,
but something that is practical… 100mH etc.
DSE sells chokes, look for the highest value in the smallest size practical.
On the other side of the choke you solder a 1uF capacitor to ground.
These two components are acting as a low pass filter. Hopefully low enough to pass DC and not
audio. I haven’t worked out exact values because it’s not all the critical. You basically want DC and not AC to get through.
Next is to solder a small diode 1N418 or even a 1N4004 to the choke and capacitor. The Kathode,
(end with the stripe) is soldered to the choke/cap.
The other side of the diode you solder a BC558
or similar transistor. (a PNP type).
The center pin (Base) is the one you solder to the diode.
The Collector you solder to ground.

The last pin left is the Emitter. This pin will be connect to earth when you put a plug into the socket.
You may need to also solder a 560 ohm resistor (depending on the voltage) to a positive rail and the emitter to pull the line high. But this depends on what the transistor is trying to ground.

[Author]

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