Powering a USB monitor

I'm considering purchasing a portable PC monitor that is powered through a USB connection vs. a separate AC adapter.  The specs for the unit say power usage is 8 watts max.  It comes with a USB cable that combines two male connectors (a Y configuration) such that one or both can be connected to the PC, depending upon the power output of the PCs ports.  The other end of the USB cable is connected to the monitor.  I wish to use this with a Toshiba NB300-N300 netbook that is about 5 years old and has 2 USB 2.0 conventional ports and one USB 2.0 charging port.  I normally have one of these ports used for a wireless mouse and another for a wireless keyboard.  This would leave only one free port for the monitor.

The website for the monitor manufacture does not provide a means to ask product questions without having proof of purchase (serial number).  Reading user reviews on vendor websites, some have had to use both USB connectors a the PC end.  I understand that USB 2.0 ports will supply 100mA at 5V without negotiation between a device and the controller, or up to 1/2 watt.  Up to 500mA (2.5 watts) can be supplied to a device through negotiation with the controller though some manufacturers will allow for greater output.  Toshiba tech support says they don't have a maximum output spec available.  So, even if I connect both USB connectors from the monitor, it seems that I can only count on a maximum of 5 watts being supplied to the monitor.  However, I don't have 2 ports available if I have both the wireless keyboard and mouse connected.

I'm wondering whether I would be able to use an AC/USB power adapter with higher maximum output (12W?) to provide power to the monitor through one of the USB connectors and plug the other side of the Y to connect to the netbook port to supply the data.

It may be difficult to provide a definitive answer but I'm trying to do what I can to avoid a blind trial-and-error situation.
ConmariAsked:
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serialbandCommented:
Wikipedia has the USB power capabilities listed.

https://en.wikipedia.org/wiki/USB#Power
   The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire to power connected USB devices.

    A unit load is defined as 100 mA in USB 2.0, and 150 mA in USB 3.0. A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0; 6 (900 mA) in USB 3.0.

If the external USB power adapter can supply 12W, then you should only need one adapter to power the 8W USB monitor.
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nobusCommented:
what monitor model is this, and what is the input reauyirement?  i suppose 5 V since you want to connect it over USB - which is not possible; usb 2 will give max 5 V at 0.5 A = 2.5 W !
and most laptops even less...so you could easily overload - burn out the chipset, or usb chips
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Michael RojekCommented:
That sounds like a recipe for disaster, why would you want a monitor powered through USB? USB is limited in wattage, so even if it will run, performance will be poor, or you risk overloading.
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serialbandCommented:
USB can provide more power for "charging" ports (Non-Data), but the max is still 7.5 W if your device was created before the new power standards.  There are new power standards for USB to support higher powered devices.
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ConmariAuthor Commented:
Thanks for everyone's thoughts.

I've just found another entry point into the manufacturer to ask a product question without having a serial number.  I've sent a message asking them to clarify the power requirement.  Vendor user's comments indicate that the unit works and I haven't read anything about their USB 2.0 controllers being blown.

Incidentally, the monitor in question is the AOC E1649FWU which I've found on both Best Buy and Amazon.  It is a very cheap unit but would come in handy for using with my netbook both around the house and while travelling since it is a 15.6" screen vs. the 10.5" built-in display.  I already have an inexpensive HannsG 15.6" VGA monitor that is attached to a stand that sits virtually permanently in one place where the netbook lives most of the time.  I'm interested in the AOC because it is cheap and more portable, in that it has a kickstand and connects via USB, and I could more easily use in other locations.  The main question is about the power requirement and how portable it would be if I would need to have an AC/USB adapter in addition to the USB connection to the netbook.  But I'm not sure it would even work when connected in this manner.  My wireless keyboard and mouse can be configured to use only one dongle but I haven't set it up that way yet.

Now that I've found a way to contact the manufacturer, I'll wait until I get more details and report back here.
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nobusCommented:
ok - interested in the outcome
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David AndersTechnician Commented:
A Google for the model number brought up many links.
including a PCMag review
http://www.pcmag.com/article2/0,2817,2399060,00.asp
TigerDirect lists it at $80
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ConmariAuthor Commented:
Here's some information from the manufacturer:

*  No reports received from field about power problems.  (I have read other user reports that both USB connectors need to be plugged in to the PC.)

*  2.5 - 8w power required, depending upon application.  (1A from two USB 2.0 ports combined equates to 5w which is adequate in most situations.)

*  A powered USB hub can be used to supply additional power if needed.  1A per port would guarantee that.  (1A from the hub and .5A from the laptop equates to 7.5w @ 5V.)

*  The monitor will not operate if there is inadequate power.  They also say that the USB controller will shut down if too much current is drawn.  (I have not verified that with Toshiba but I have found the following Q&A links which refer to the USB spec:

http://electronics.stackexchange.com/questions/53747/is-it-safe-or-even-possible-to-draw-more-power-from-a-usb-port-than-it-was-des

http://www.microchip.com/forums/m274097.aspx

I have also configured my Logitech wireless mouse and keyboard to operate from a single dongle through their unifying utility so that I will have two free USB 2.0 ports available for use with a portable monitor.

Based on the above, I'm going to purchase the AOC unit and will report back the results.
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nobusCommented:
i found most laptops do not provide the max, and stay well below it
i would never recommend loading the usb port like this
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ConmariAuthor Commented:
Question status:  Just received the monitor and hope to install and try out later today.  Will report what I find as soon as possible.
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ConmariAuthor Commented:
Have installed the included driver and monitor utility and connected the monitor using both USB connectors of the Y cable provided.  Monitor works great.  Quality reasonably good -- about what one would expect for the price ($90).  Did have a possible problem with initial drive install (a Norton Internet Security program error ensued, though not sure about the cause and effect).  Uninstalled/reinstalled the driver and utility and problem has not recurred.

Want to get some more time with this before I pass judgment but so far so good.
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ConmariAuthor Commented:
The USB monitor continues to perform well -- no flicker or intermittent power issues.  Again about the quality of an average built-in laptop screen.

I did encounter one of those unexpected consequences but finally found a workaround.  I often use the netbook to remotely access my main system located elsewhere in the house and Windows Remote Desktop works just fine with the new USB monitor connected.  However, I found that after doing so, when I returned to the host PC and logged on directly (vs. remotely), the color settings of the VGA monitor attached to the host were all messed up.  I finally realized that somehow this configuration (using the USB monitor on the netbook) changed the Intel video driver settings on the host and I could not adjust the settings through the host driver panel to return to the previous video status.  I finally tried disconnecting and reconnecting the monitor from the host while the host was under local control and that fixed the problem.  More of an annoyance and distraction rather than a long-term issue but a strange secondary effect.  Previously, remotely controlling this same PC from the netbook with a VGA monitor attached has never caused the same thing to happen.

So I am pleased with this USB monitor and hopefully it will continue to perform well.  It would seem that the 8 watt power usage listed in the specifications is an outside maximum (under what circumstances?) and the 5 watts supplied from the two USB ports is adequate.  I'm pleased that, so far, I don't need a separate powered USB hub for additional power because that would make the USB monitor that much less portable.
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ConmariAuthor Commented:
All of the responses made me realize that more information was necessary which I ended up eventually getting from the manufacturer.  In the end, this was still somewhat of a trial-and-error solution based on what I learned to give me a reasonable comfort level.
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