ac power adapter polarity readings cause I'm confused...

[Miguel2013]

I bought 2 ac dapters for usb hubs and they work great however, I need a third one with 4A to increase current for the host devices from 2A currently on the hub.
I am scared now for polaritys don't wanna damage anything so, I wanna buy the right polarity one.

-I have 3 usb hubs, 1 usb 2.0 with 4A ac adapter works great, 1 usb 3.0 with 4A ac adapter works great but i want a 4.0 and, 1 usb 3.2 with 2A works great.

the pic on the left is on my usb 3.2 hub I just need the right polarity, how do i got about buying it?

 

[jsfitz54]

I bought 2 ac dapters for usb hubs and they work great however, I need a third one with 4A to increase current for the host devices from 2A currently on the hub.
I am scared now for polaritys don't wanna damage anything so, I wanna buy the right polarity one.

-I have 3 usb hubs, 1 usb 2.0 with 4A ac adapter works great, 1 usb 3.0 with 4A ac adapter works great but i want a 4.0 and, 1 usb 3.2 with 2A works great.

the pic on the left is on my usb 3.2 hub I just need the right polarity, how do i got about buying it?

Most hubs are center pin positive.

Example from your picture:

Outer barrel is negative and center pin is positive.

Always look at picture diagram.

 

[Vario]

I bought 2 ac dapters for usb hubs and they work great however, I need a third one with 4A to increase current for the host devices from 2A currently on the hub.
I am scared now for polaritys don't wanna damage anything so, I wanna buy the right polarity one.

-I have 3 usb hubs, 1 usb 2.0 with 4A ac adapter works great, 1 usb 3.0 with 4A ac adapter works great but i want a 4.0 and, 1 usb 3.2 with 2A works great.

the pic on the left is on my usb 3.2 hub I just need the right polarity, how do i got about buying it?

You use the symbol on the AC adapter, it will tell you if the external "sleeve/barrel" on the plug (the part that entering the device) is 'plus' or "minus" polarity.
Example:

means that the external sleeve is plus.

means that the the external sleeve is minus.

You can use a digital multimeter to check it.

 

[Miguel2013]

external sleeve? that's up or down on the tip?

 

[caroline!]

Hi.

The diagram resembles the barrel connector viewed from the top, the outermost part or sleeve is symbolised with the semicircle and the internal contact with the dot. Most have the sleeve with a negative polarity because that's the thing you can touch.
In the two pictures you've uploaded the diagram is exactly the same, just in different positions.

 

[Bill_Bright]

Most hubs are center pin positive.

^^^This^^^ And for all sorts of reason too, but most significantly, safety. With the positive voltage in the center (and ground on the outer ring), that + voltage is much more protected from accidental shorts should the plug fall on to the metal case, for example.

Still it is important to verify polarity whenever attempting to combine voltage sources. The thing to remember is, with DC voltages, "parallel adds current, series adds voltage".

 

[caroline!]

^^^This^^^ And for all sorts of reason too, but most significantly, safety. With the positive voltage in the center (and ground on the outer ring), that + voltage is much more protected from accidental shorts should the plug fall on to the metal case, for example.

Still it is important to verify polarity whenever attempting to combine voltage sources. The thing to remember is, with DC voltages, "parallel adds current, series adds voltage".

I'm more worried about the hubs being 'dumb' as in, internally they're just a series of ports connected in parallel.

I mean that's usually not an issue unless you want to start pulling large amounts of current, if they're connected using wires those could get too hot if there's no current limiting circuitry. I wouldn't use a hub to power something that pulls 4 amps, better power it directly.
For reference I have a lamp using about 3.5 amps and the whole wire gets hot after a while, it can take it as it's within normal operating conditions but at one point I had it on a cheapo adapter that *claimed* it was 4A and it literally melted the wire until it shorted, there was no fire or anything just a spark and smoke, and that was the end of that.... replaced it with the cable & PSU I'm using now. Don't go too cheap on adapters or that happens.

 

[eidairaman1]

Look at the hub itself and get the required adapter

 

[Bill_Bright]

I'm more worried about the hubs being 'dumb' as in, internally they're just a series of ports connected in parallel.

I am not following.

There are 2 separate circuits in typical USB connections; data and power. NO WAY are you going to overload the data circuits to the point heat is even remotely going to become an issue.

As for power, each hub has its own power supply. The only place excessive current (and thus heat) could become an issue is with the wall outlet. But only after you connect dozens of adapters to a single outlet.

Look at your adapters again. In terms of heat, don't worry about the DC output current. Look at the AC input. In your first image, that adapter draws a mere 0.4A. The 2nd adapter just 0.7A. Most wall outlets are rated for at least 15A (in older homes), typically 20 to 25A.