Soldering Wires to 3.5mm Jack?

[Synomenon]

Ok, I'm trying to make a custom 3.5mm jack for a project. The 3.5mm jack I have is a 4-pole / 4-conductor jack:

This is the cable I'm trying to solder to it:

There are four terminals on the jack, but only three wires on this cable. The three split ends do merge into one wire (see the 3.5mm end of the cable).

Where is that fourth wire? One is supposed to be for composite video, one for left channel audio, one for right channel audio and I think the fourth is for shield / ground, but I don't see a separate shield / ground wire.

 

[magomago]

continuity test to see if the 4th wire is linked at all to any of the other three?

find out which ones you need, solder it roughly and test it out in your setup, confirm all is well, re-solder it more nicely if you are particular about that, and call it a day?

 

[Throckmorton]

Are you sure that's a real 4 wire cable?

 

[Synomenon]

DP

 

[Synomenon]

continuity test to see if the 4th wire is linked at all to any of the other three?

find out which ones you need, solder it roughly and test it out in your setup, confirm all is well, re-solder it more nicely if you are particular about that, and call it a day?

How do I perform a "continuity test"? I'm not an electrician and have only ever soldered what you might as well call wire hangers.

Are you sure that's a real 4 wire cable?

This is the cable:
http://www.amazon.com/Jensen-Audio-V.../dp/B001EY7HQQ

I've seen some websites mention it's a 4-pole cable. I cut off the RCA connectors already (tagged each wire so I'd know which RCA connector it had on it (yellow, red, white).

 

[Synomenon]

This is what I'm planning to do:

I have a head unit in my car that has a rear USB input. So I installed one of these in my glove box:

My current head unit requires only an iPod / iPhone dock connector to USB cable (the standard iPod / iPhone sync / charge cable).

My new head unit requires one of these cables (that 3.5mm plug is a 4-pole / 4-conductor plug):

So, instead of drilling a hole next to that flush mount USB port in my glovebox to feed that 3.5mm part of the new cable through, I want to install that flush mount 3.5mm 4-pole / 4-conductor jack (in the first post) next to the flush mount USB port I already have in the glovebox.

 

[Synomenon]

Ok, I found the "fourth wire" I cut the cable past that triangular part where the three ends merge into one and after that triangular part there's a bare wire wrapped around all three of the main (red, white, yellow) wires.

 

[corkyg]

That normally would be a common ground. The wrap around also acts as a shield for the three other wires.

 

[Synomenon]

Now I just need to figure out which contact on the 3.5mm jack goes with which wire.

 

[stahlhart]

Now I just need to figure out which contact on the 3.5mm jack goes with which wire.

Those among us who own a soldering iron typically also own a DMM. 🙂 Less than ten bucks at Harbor Freight Tools.

 

[Zap]

How do I perform a "continuity test"?

You need a digital multimeter. They are an essential part of any toolbox.

Ok, I found the "fourth wire" I cut the cable past that triangular part where the three ends merge into one and after that triangular part there's a bare wire wrapped around all three of the main (red, white, yellow) wires.

Yup, the ground. I think it usually goes to the tip of the 3.5mm plug, or the innermost part of the jack.

 

[bruceb]

If you look at the back of the Jack you bought there should be numbers 1 thru 4 marked on the plastic. The photo below shows which terminal on the plug is which.
It starts at the very Tip #1, the first ring is #2, second ring is #3, barrel or last ring is #4

 

[OR-G]

Yeah like everyone else said, a DMM will make life easy. I have a craftsman one from sears during a sale for $10. I also purchased a harbor freight one for $3 during a sale. The harbor freight one is decent and can get the job done (keep it in my car), but I have had some random issues with it. Definitely prefer the craftsman when working with electronics.

Did find this site for you. Looks like the TRRS cable is for audio left/right ground and mic. http://benttronics.blogspot.com/2009/05/audio-breakout-cable-for-ipodiphone.html

Still would suggest buying a DMM for future projects. Have the correct tools today and you won't have to keep going to the store.