I have a 12v USB hub and it has 3 pin to connect power to it as pictured below. The + and the ground seems to have two pins. Which would I connect the ground to? both? why would it have two ground pins?

Picture below:

 

hi john,
As you may have seen the +24v and GND have a White bar to identity the pins, its not unusual for manufacturers to use what type of connectors they have lots of in stock.

E

 

Both the center and right contacts on the green connector are labeled ground so use either one.

 

Which would I connect the ground to? both?

One or the other, but not both.

It looks like the two connections on the right are both ground, but it isn't clear due to the angle of your picture. If you have any doubt, use a continuity checker.

 

I agree with Eric that the centre and RH terminal appear to be common, if so, one may be for connecting to earth ground, in a PC, the common would be bonded to earth anyway.
Especially if this is a stand alone unit.
Max.

 

That's what I thought but then when I removed the connector which is removable then the pin labels look like below so it's a little confusing

 

Does appear to be offering an ability to bond to earth GND!?
Max.

 

pin labels look like below so it's a little confusing

The right two pins are ground.

 

hi john,
Some power cables use a two core screened, can you see how the Plug is wired.?
E

 

I found the user manual link below for it, but cant be certain which pin to use for ground

https://sgcdn.startech.com/005329/media/sets/st4200usbm_manual/st4200usbm.pdf

 

I found the user manual link below for it, but cant be certain which pin to use for ground

It doesn't matter. Use both if you're a belt *and* suspenders type.

 

It doesn't matter. Use both if you're a belt *and* suspenders type.

so just using the outer one and leaving the middle one off completely is fine?

 

so just using the outer one and leaving the middle one off completely is fine?

Yes. If it came with a supply, was it using both grounds? That wouldn't make much sense because the ground connection carries the same current as the power connection.

 

Yes. If it came with a supply, was it using both grounds? That wouldn't make much sense because the ground connection carries the same current as the power connection.

No it doesn't come with power supply. I've wired it with the outer pins and left out middle one and seems to be working fine so far. I did a continuity test between the two ground pins and the multimeter beeps. But then again it seems the continuity beeps between any pins lol.