Confusion with 3.5mm jack pinout

Thread Starter

majhi

Joined Jul 2, 2014
55
Hello all. I am currently making a project that uses a DFPlayer Mini connected to an Arduino. In order to use a speaker and aux cable that I already have, I ordered some cheap 3.5mm jacks from eBay, but am a little puzzled by the pinout I found on Sparkfun (https://learn.sparkfun.com/tutorials/connector-basics/audio-connectors). The image that they have says that the outermost pins are tip/ring, however in disassembling the jacks that I received, they look slightly different.

While pin 1 (see my photo) does, in fact, seem to be tip, I can't tell what pin is ring because it looks like pins 3 and 4 are touching (internally) without any cable plugged in. Indeed, it seems as though pin 3 is the one that actually touches the ring of the cable's plug. So which one should I wire to the DFPlayer Mini, 3 or 4? Lastly, since pin 5 touches the sleeve, do I have to wire that to ground? Thank you in advance!

stereo jack.jpeg
 

Audioguru again

Joined Oct 21, 2019
6,672
Sparkfun says that there is an internal switch that connects pin 1 to pin 2 and connects pin 3 to pin 4 when no plug is inserted.
Then a circuit can determine that a plug is inserted and the jack can disconnect stereo speakers when stereo headphones are used with this jack.
 

Thread Starter

majhi

Joined Jul 2, 2014
55
Sparkfun says that there is an internal switch that connects pin 1 to pin 2 and connects pin 3 to pin 4 when no plug is inserted.
Then a circuit can determine that a plug is inserted and the jack can disconnect stereo speakers when stereo headphones are used with this jack.
Alright thanks, I'll just use the outermost pins then. Yeah, I can see the switch between 1 and 2 because it's very clearly visible. If I squint really hard, I think I can see the break in the connection between 3 and 4 when the cable is plugged in. They look like they're still touching - the movement of the switch is almost imperceptible. So what should I do with 5 then?
 

jpanhalt

Joined Jan 18, 2008
11,087
It looks like a switched jack as has been stated. If used for power, which is an alternative use, you would need to decide whether to switch the negative or use reversed polarity with a negative pin. That's not what you are doing, so ignore the switch. Use your ohmmeter to decide which pins to use.
 

Dodgydave

Joined Jun 22, 2012
11,284
Hello all. I am currently making a project that uses a DFPlayer Mini connected to an Arduino. In order to use a speaker and aux cable that I already have, I ordered some cheap 3.5mm jacks from eBay, but am a little puzzled by the pinout I found on Sparkfun (https://learn.sparkfun.com/tutorials/connector-basics/audio-connectors). The image that they have says that the outermost pins are tip/ring, however in disassembling the jacks that I received, they look slightly different.

While pin 1 (see my photo) does, in fact, seem to be tip, I can't tell what pin is ring because it looks like pins 3 and 4 are touching (internally) without any cable plugged in. Indeed, it seems as though pin 3 is the one that actually touches the ring of the cable's plug. So which one should I wire to the DFPlayer Mini, 3 or 4? Lastly, since pin 5 touches the sleeve, do I have to wire that to ground? Thank you in advance!

View attachment 195432
Pins 1, 4 are the jackplug connectons,and from the audio amplifier,
(left, right, tip and ring)
2, 3 would be the speakers connections, which would be disconnected when the jackplug is inserted.
 

RobNevada

Joined Jul 29, 2019
66
A meter doesn't lie. Use an ohm meter to verify pins. You need to then know whether the center pin is + or - for your circuit and wire it that way.
 

ci139

Joined Jul 11, 2016
1,898
it separates the channels from their alternate returns (to loudspeakers)
if the plug is inserted . . . so it should have Ls Rs Lx Rx Gnd
random schematic
 

MisterBill2

Joined Jan 23, 2018
18,167
If you really want to be certain about the connections you need two tools, first an ohm meter with a reasonable low ohms scale, where you can read values below ten ohms, and you need a stereo jumper cable with a 3.5mm stereo plug on each end.
First, use the ohm meter to verify that the cable ir correct, tip to ti0p, ring to ring, and sleeve to sleeve. THEN plug the cable into that jack that you are wondering about and put one lead from the ohm meter onto the sleeve of the other end of the cable. and see what pin on the jack body has the low resistance. Next do the same with the tip. and finally do it with the ring on the plug.
That gives you the actual connections directly, independent of any web page that may or not describe the jack that you have.
 

RobNevada

Joined Jul 29, 2019
66
Mister Bill2 is right. Plug in the cable and meter the ends of the cable. You also need to use the matching cable to your jack. If it is a mono jack then use and mono cable. If it is a stereo jack then that type of cable. The reason for using the correct cable is that the rings on the cable have rings to separate the polarity. If the leaf arms (+ and -) inside the plug are resting on the same metal band you will short the circuit at that point and any audio will not get any further.
 
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