Micro USB Power cable -- which are the power pins

[[email protected]]

If this is a slightly off topic query,
I apologize. Could some electronics guru
please help ? I am not at all familiar
with the micro USB power cable, and here
are some questions:

1. As I understand it, the USB cable
has a micro USB connector on one end,
and a regular USB connector on the
other. The power is fed in via the
regular USB connector, and the micro
USB connector plugs into the device
that uses it. So, where do I connect
the regular USB connector to, for the
device at the other end to receive
power over the USB cable. In my case,
the receiving device needs a power
supply that can supply 700 mA
(max) at 5V. I can easily build a
power supply to these specifications,
and so could I just put a matching
connector at the regular USB connector
end of the cable, and then power
the device this way.

Please let me know your thoughts on
this.

 

[Sylvia Else]

If this is a slightly off topic query,
I apologize. Could some electronics guru
please help ? I am not at all familiar
with the micro USB power cable, and here
are some questions:

1. As I understand it, the USB cable
has a micro USB connector on one end,
and a regular USB connector on the
other. The power is fed in via the
regular USB connector, and the micro
USB connector plugs into the device
that uses it. So, where do I connect
the regular USB connector to, for the
device at the other end to receive
power over the USB cable. In my case,
the receiving device needs a power
supply that can supply 700 mA
(max) at 5V. I can easily build a
power supply to these specifications,
and so could I just put a matching
connector at the regular USB connector
end of the cable, and then power
the device this way.

Please let me know your thoughts on
this.

A micro USB power cable is just a micro USB cable that doesn't have the
data line wires.

You can still plug it into into a computer (laptop, or otherwise), just
to access the power.

You could also plug it into something like this

http://www.ebay.com/itm/Dynex-Dual-...366312?pt=PDA_Accessories&hash=item257b6a7ce8

Sylvia.

 

[Richard Henry]

If this is a slightly off topic query,
I apologize. Could some electronics guru
please help ? I am not at all familiar
with the micro USB power cable, and here
are some questions:

1. As I understand it, the USB cable
has a micro USB connector on one end,
and a regular USB connector on the
other. The power is fed in via the
regular USB connector, and the micro
USB connector plugs into the device
that uses it. So, where do I connect
the regular USB connector to, for the
device at the other end to receive
power over the USB cable. In my case,
the receiving device needs a power
supply that can supply 700 mA
(max) at 5V. I can easily build a
power supply to these specifications,
and so could I just put a matching
connector at the regular USB connector
end of the cable, and then power
the device this way.

Please let me know your thoughts on
this.

You may find many devices are not capable of providing 700 mA. Common
protective devices limit output power to 500 mA.

 

[whit3rd]

You don't need to find the pinout, unless you want to wire to the plug.
NO ONE wants to manually wire to a mini-USB plug; just buy a
prewired cable/plug assembly (or, equivalently, sacrifice a cable
or an unsatisfactory power adapter).

Just use your voltmeter on the unsatisfactory adapter's output wires
to find the right polarity, before you cut the cable off.

 

[hamilton]

We power several of our gadgets through a micro-USB. We just buy a Samsung
universal AC-to-USB brick for about $4, good to 700 mA. We recently added a 2
amp version to stock, to power some bigger stuff. Be careful... there are a lot
of really bad, really cheap USB power supplies around.

Here's an example product:

http://www.highlandtechnology.com/DSS/T165DS.shtml

https://dl.dropbox.com/u/53724080/SED/T165_USB_sch.jpg

I see you ground all the signal lines.

Do you not need the USB connectivity or ignore just those lines ?

hamilton

 

[[email protected]]

I see you ground all the signal lines.

Do you not need the USB connectivity or ignore just those lines ?

hamilton

The data lines are normally numbered 2 and 3, 4 is ID
So I'm guessing most of the grounded pins are actually mechanical

If you don't need usb but just power I think the standard says you
should short d+ and d- to signal that you want high current

-Lasse

 

[[email protected]]

Right. We generally assign a pin number to all the mechanical pads, to remind us
to ground them or not. That board gets power only, no USB communications.Other
boards do real USB, generally through an FTDI serial chip.




Interesting. I wonder if the power supplies are smart enough to notice.

some of them probably are: www.ti.com/lit/ds/symlink/tps2511.pdf

But I think most of what a chip like that does is signal to the
device
how much power it can expect, so say a tablet can charge at 2A when
connected to a charger and at 500mA when connected to a computer

I guess you could use that, so if someone plugs your device into a
computer
that will only supply 500mA, you can tell him it won't work

-Lasse

 

[[email protected]]

   That was the USB 1.0 standard.  2.0 was 1A

2.0 is also 500mA, 3.0 that is up to 900mA when running high speed,
something like 1500mA when it is for charging

-Lasse

 

[Jasen Betts]

You may find many devices are not capable of providing 700 mA. Common
protective devices limit output power to 500 mA.

these protective devices aren't particularly common in the wild.

 

[josephkk]

The data lines are normally numbered 2 and 3, 4 is ID
So I'm guessing most of the grounded pins are actually mechanical

If you don't need usb but just power I think the standard says you
should short d+ and d- to signal that you want high current

-Lasse

No need to guess. The standards are available here:

http://www.usb.org/developers/docs/

Nice price as well.

?-)