Category Archives: News

Long VGA Cables and EDID

Some projectors and TVs won’t display anything when connected to a computer via the USB 3.0 to VGA graphics adapter, however they do display when connected to a computer via the VGA port or a USB 2.0 VGA adapter. What is going on here?

DisplayLink’s USB 3.0 generation products have a different behavior from the USB 2.0 generation — they disable themselves if nothing is attached. HDMI and DVI have a pin for hot-plug detection, but VGA does not. So the only way to know if a monitor is attached with VGA is if the monitor’s display information (EDID) can be read over the VGA cable. But there are cases where EDID information is lost, like with long (+10ft/3m) VGA cables  – in these cases, the USB 3.0 VGA adapter will assume there’s no display there.

Background

To understand what is happening we need to take a step back and look at the EDID standard. EDID, or Extended Display Identification Data, is information that is stored on most external displays. The EDID information contains a slew of display specific information like refresh rates, preferred timings, native resolutions, color space, audio capabilities, and other manufacturer details.

Normally, when you connect a 1920 x 1080 monitor directly to your computer, the graphics card tries to communicate with the display to read its EDID. If succeeds, it will learn that the monitor resolution is 1920 x 1080 and will output the proper 1920 x 1080 image. However, if EDID is not present, the graphics card will make a naive decision on what resolution to output to the connected monitor. Instead of getting a 1920 x 1080 image on your large monitor, you can end up with a resolution of 640 x 480 on a 1920 x 1080 display. The key point is that even without an EDID, the computer still outputs an image.

But for the USB 3.0 VGA adapter, having no EDID looks the same as having no monitor attached at all. So when can this happen?

Some TVs do not report EDID. Unfortunately, there is no simple solution to get these TVs to work as an external monitor using the USB 3.0 to VGA adapter. The only workaround is to either use the USB 2.0 to VGA adapter or a direct VGA port on the computer instead of the USB 3.0 to VGA adapter.

While most projectors do report their EDID information, many projector setups have lengthy VGA cables involved (e.g. ceiling projectors). When using a long VGA cable (+10ft/3m) the signal on the line where EDID is being read can get degraded and will not be visible to the USB 3.0 to VGA adapter. The solution around this is to either connect the VGA cable directly into the computer via a native VGA port, use a shorter VGA cable, or to use the USB 2.0 to VGA adapters that might not set an optimal mode without EDID, but will try a default mode at least.

Plugable BT-STAND Delivers Superior Audio Quality and Great Battery Life

The new Plugable Bluetooth Speaker Stand puts out at least four times more sound than the iPad’s built-in speakers.

Testing with a dB meter clearly shows how and why the BT-STAND sounds so much better than the tiny speakers in most phones and tablets.

Maximum dB and Frequency Response Testing Methodology:

  • How we measured dB: SL-824 Digital Sound Level Meter @ 12 inches away from the source.
  • Ambient room noise: 34dB in our lab.
  • Sample song: “Coldplay – Paradise”, Source: Youtube
  • 20Hz-20000Hz sweep: “Hearing Test HD”, Source: Youtube
  • Playback Device: iPad Retina

Q: What exactly is a “dB”?

A: Gain (volume/loudness) is typically measured in Decibels (dB). They are expressed on a logarithmic scale, where a 3dB increase sounds twice as loud. This means 96dB sounds twice as loud as 93dB, and 99dB sounds twice as loud as 96db. (http://en.wikipedia.org/wiki/Decibel)


When testing the average dB (loudness) from the BT-STAND we wanted to use a popular sample song that had a good range of volume and really flowed from deep bass to high treble. We chose “Coldplay – Paradise”.

We set the iPad at its maximum Bluetooth audio volume, and found the average dB for this song at that setting was 95dB with a peak of 103dB. We repeated the test using the 3.5mm auxiliary input. Both methods peaked at identical volumes. However, Bluetooth had much less distortion than the 3.5mm aux cord. We recommend using Bluetooth unless your playback device doesn’t have it.

test

When played through the iPad Retina’s built-in speakers only, the average volume from our sample song was 80dB and peaked at 95dB. It sounded OK, but was very quiet in comparison.

test2

When testing maximum dB levels we learned that the BT-STAND is capable of sustained outputs of up to 112.5dB at around 8Hz-8.5kHz on a 20Hz-20kHz sweep with almost no distortion at all. This is extremely impressive for such a small device. The volume was so loud, I had trouble staying in the same room during the test.

During the 20Hz-20kHz sweep on the iPad, a peak of 104.8dB was recorded, but with heavy distortion. We stopped the test early to avoid permanently damaging the iPad speakers.

In this comparison of volume, going back to the dB scale for reference, our BT-STAND is at least four times louder than the iPad Retina!

The frequency response from the BT-STAND can be “heard” (vibrations can be felt from the internal 1.5″x0.75″ passive radiators more than heard) as low as 20Hz but usable audio starts at 45Hz and ends at about 14kHz (this may just been the limit of my ears). This is on par with our manufacturer’s specs of 50Hz to 20KHz, assuming my ears aren’t very good in the higher end of the spectrum.

When we tested the iPad’s frequency response, we were not surprised when we discovered it was severely lacking, with usable audio starting at just over 100Hz. No low-end bass response at all! Again the range ended around 14kHz, which might just be my ears.

Battery Life and Charge Testing:

Over the course of a few days in our office, the BT-STAND got almost 12 hours of on-and-off medium volume playback over Bluetooth on a single charge. In our opinion, this was extremely impressive, especially considering the small size and lightweight design of the unit.

_DSW4223_256_DSW4224_256

Charging the BT-STAND from its low battery warning beep to a full charge takes about 5 hours using any USB charger. While charging we found the BT-STAND only pulls about 0.2A, so it won’t matter if you are charging from a USB port on your computer, a USB hub, or a dedicated charger. We suggest you plug it in at the end of the day and let it charge up overnight. It will be ready to go in the morning!

_DSW4228_256

Where to Buy

Plugable Premium Bluetooth Stereo Speaker with Integrated 3-Point Folding Tablet / Phone Stand for A... Product Details
$39.95

Plugable Launches Adapter to Enable Charging on Any Powered USB Port

It’s frustrating, but many devices won’t charge on a powered USB port the way you’d expect. This includes most Apple, Samsung, and Google phones and tablets.

This is because the phone must choose how much power to pull, and by the original USB spec devices are supposed to only draw 100mA at first. They can then negotiate up to 500mA. This negotiation requires a PC that’s attached and on.

The iPhone and most other non-tablets will charge at 500mA on a standard USB port this way. But they can also charge faster (up to 1000mA) if a port sends a special, non-standard signal to say “I’m an Apple 1A charger”. It does this by shorting the data lines (disabling data transfer at that point) and putting a specific signal voltage on each of USB’s two data lines. Even though it’s not a standard, nearly all phones and tablets on the market today recognize this signal.

For tablets like the iPad, this mechanism is even more important. Because these batteries are larger, charging at 500mA would be slow. The 1A “I’m an Apple charger” signal becomes the minimum for the tablet to report charging at all.

This new Plugable USB-MC1 Charging Adapter simulates that 1A signal, turning any powered USB port with at least 1A power available into a charging port.

Charging both a iPad 4 and iPod 3

Charging both a iPad 4 and iPod 3

This also has the effect of disabling data transfer, so you can safely plug your phone or tablet into a public computer and the phone or tablet will charge, but not be visible to the computer otherwise — you’re safe to charge without worrying about exposing your data.

Leave this attached to your phone or tablet’s USB charging cable to greatly expand the set of USB ports you can charge on.

iPad Not Charging        Ipad Charging

Above on the left is an Apple iPad connected to a standard USB hub that has plenty of power available, but you can see on the iPad’s screen in the upper right, that it’s not charging.

On the right is the same setup with our adapter in-between the iPad and the hub. You can see the iPad now sees the hub as a charger, and is charging the battery.

How many of these adapters can be safely used on a powered hub at once?

The AC adapter of your powered hub needs to be rated for at least 1A per USB charging adapter connected. If it is not, over-current may be triggered (causing all power to the hub to shut off), or the hub circuit or power supply may heat up from too much current being pulled through by the device. If this happens, remove devices until you’re back within the rated amperage.

So before you go running off and buy 10 of these little dongles to turn your 10 port hub into a charging super station, keep in mind that you are still limited by how much power the USB hub has access to. For instance, our 10 Port USB 2.0 Hub comes with a power supply of 2.5A, that is only enough to actively charge 2 devices at the Apple 1A Charger rate with .5A left for spare devices on the hub.

More questions?

The Plugable USB-MC1 product page has more detail, including a table of charging rates with some common phones and tablets. Have any other questions? We’re happy to help. Feel free to comment below or email support@plugable.com anytime. Thanks for your support of Plugable products!

Where to buy

Plugable Power USB Universal Fast Charge-Only Adapter for for Android, Apple iOS, and Windows Device... Product Details
$7.95

BT-STAND with music notes for website

Plugable Launches New Bluetooth Wireless Speaker with Integrated Tablet/Phone Stand

Have you ever wanted to watch a movie or listen to music on your tablet or phone, only to be frustrated by the awful sound from the tiny built-in speakers? Plugable has got you covered! The BT-Stand, our new Bluetooth wireless speaker, delivers surprisingly rich and resonant sound, while doubling as a stand for your tablet or phone. Compact and lightweight, it’s the perfect companion for your tablet or phone when you are on the go.

Plugable Bluetooth Wireless Speaker Tablet/Phone Stand with NFC Pairing

Plugable Bluetooth Wireless Speaker Tablet/Phone Stand with NFC Pairing

The BT-Stand’s lithium-ion battery lets you enjoy up to 10 hours of surprisingly rich, full sound, and easily recharges using the included micro USB cable. With 5 watts of power, 50Hz to 20KHz frequency response, and 85dB sound, it gives you surprising volume with very little distortion. It delivers great-sounding enhanced bass though its two 1″ main speakers and four internal 1.5″x0.75″ passive radiators with external bass reflex ports.

_DSW4223_256

A great feature of the BT-Stand is support for Near Field Communication (NFC). NFC allows compatible devices like many tablets and smartphones to read connection information directly from the BT-Stand via radio when they are held next to each other. This makes pairing fast and easy. Simply align the NFC logos and tap to pair the two devices and stream your music.

Any device that supports the A2DP Bluetooth stereo protocol should work with the BT-Stand. When pairing it with a computer, we highly recommend our own Plugable USB-BT4LE Bluetooth 4.0 USB adapter. The BT-Stand also features an auxiliary 3.5mm audio input jack for use with the standard headphone output found on most non-Bluetooth devices such as iPods, other MP3 players, computers, and other devices.

_DSW4228_256

The BT-Stand features solid construction with a compact V-Frame design that supports your tablet or phone and can be adjusted to multiple viewing angles. Most phones and tablets will fit, with or without a protective case or sleeve. Rubber feet provide maximum stability.

 phone_256

Plugable’s new BT-Stand offers a huge improvement in both volume and quality of sound over the poor-sounding integrated speakers typically found on tablets, phones, and laptops. Its compact foldable design lets you stick it in your tablet or laptop bag, backpack, or purse and bring it along wherever you go. It’s the perfect companion on road trip or vacation. Take it to the beach or park and enjoy some quality sound. You imagination is the only limit to where you can go with it!

Where to Buy

Plugable Premium Bluetooth Stereo Speaker with Integrated 3-Point Folding Tablet / Phone Stand for A... Product Details
$39.95

DisplayLink Apple Mac OS X 2.1 Beta now available

DisplayLink has released a beta of their new version 2.1 drivers (Sept, 2013) for Apple Mac OS X 10.6 – 10.9.

This new 2.1 driver has many improvements over the previous Mac OS X version 2.0 drivers (March, 2013). In short, it’s a must-have install for Mac users on 10.8.5 and earlier. It supports all existing DisplayLink-based USB 2.0 and USB 3.0 adapters and docks, including Plugable’s. And it’s a first step towards 10.9 support.

Here are the details.

Limited support for OS X Mavericks (10.9)

Mavericks requires updated USB graphics drivers. 2.1 is the first version from DisplayLink with support for 10.9. However, it is very rough support, with a long list of limitations, detailed below.

Once Apple and DisplayLink have further updates leading up to the release of 10.9, Apple multi-monitor enthusiasts will have a lot of improvements to look forward to, in terms of improved multi-monitor support. From Apple’s OS X Mavericks page:

There’s no longer a primary or secondary display — now each has its own menu bar, and the Dock is available on whichever screen you’re working on. You can have multiple app windows running on either display. Or run an app full screen on each one. Even show a desktop on one display and a full-screen app on another.

Support for Dual Head Docks

DisplayLink 2.1 supports the latest firmware configuration format for the latest docks and adapters, and adds support for the new Plugable UD-3900 docking station, offering dual HDMI/DVI display outputs as well as ethernet input, 2 USB 3.0 ports, and 4 USB 2.0 ports.

Ethernet bug fixes

The DisplayLink Mac 2.0 driver was the first to offer support for the DL3500 chip’s ethernet functionality. This initial release revealed a few wonky issues with ethernet on our USB 3.0 DisplayLink based product, like the Plugable UD-3000 docking station. Most common was the issue of network disconnections- where the network cable would show being unplugged even when it was actually connected.

DisplayLink 2.1 resolves all known instances of these problems, allowing you to surf in peace.

What limitations and problems remain on Mac?

For technical users on OS X seeking to maximize workspace and productivity, DisplayLink’s 2.1 driver is a big step forward. However, there are still important issues to consider:

  1. Mac OS X will not support USB 3.0 audio until 10.8.5 / 10.9. Until then, audio on a dock or display will not work when connected via USB 3.0. This is an Apple limitation. Fortunately, Apple’s support for this is coming soon.
  2. Mavericks 10.9 breaks existing USB graphics drivers. While this version 2.1 driver has some early support for 10.9, there are still many issues remaining. DisplayLink calls out these issues:
    • Screen corruption and layout issues when adding more than one additional DisplayLink monitor.
    • Some applications using single buffer rendering may flicker on DisplayLink monitor.
    • Scrolling pages in Safari may cause corruption on DisplayLink screen.
    • Playing movie in QuickTime may cause the title bar to flicker.
    • Fast user switching may not work correctly when using DisplayLink monitors.
    • Sometimes rotating one DisplayLink monitor rotates a different display.
    • Sometimes when DisplayLink monitor is set as primary after waking up from sleep it is disconnected and there is no login screen visible.
    • Corruption on the screen may be visible while rotating DisplayLink displays.

    In short, until DisplayLink and Apple have further updates for 10.9, DisplayLink users should avoid the upgrade to 10.9 if possible.

  3. DisplayLink’s OS X 2.1 driver relies on system CPU and not GPU processing, so the video and application-specific notes in our previous blog post, DisplayLink USB Graphics and OS X Limitations, remain relevant.

The bottom line is that DisplayLink 2.1 fixes a number of larger bugs relating to ethernet and dual display outputs under OS X 10.8 “Mountain Lion” and provides initial support for OS X 10.9 “Mavericks”. This makes our USB 3.0 docking station products a whole lot better on OS X. Just keep in mind that this is still in beta, and it may introduce its own little quirks.

Additional details and the driver .dmg download are here:
DisplayLink 2.1 OS X Beta Forum.

We’re here to help and we welcome your questions. Email support@plugable.com anytime, or just comment below. Thanks for going out of your way for Plugable products!

Plugable UD-3900 USB 3.0 SuperSpeed Universal Docking Station with Dual Video Outputs for Windows 8.... Product Details
$99.00

Plugable UD-3000 USB 3.0 SuperSpeed Universal Docking Station for Windows 8.1, 8, 7, XP (HDMI and DV... Product Details
$89.00

New 2013 Google Nexus 7 and USB Ethernet Adapters

The new 2013 Google Nexus 7 (“Gen 2″ or “flo”) has a bug where USB Ethernet adapters won’t work — they’ll appear to be recognized, but won’t get a DHCP address.

This is with Android 4.3, builds JSS15J and JSS15Q at least.

There is an open bug on this issue, we we’re hopeful that Google will fix quickly with an update:
https://code.google.com/p/android/issues/detail?id=58868

Until then, it’s important to realize that USB Ethernet adapters won’t work. So far, there is no evidence of this affecting other devices (e.g. the original Nexus 7 is not yet affected).

In combination with a USB OTG cable, it’s common to use USB Ethernet adapters to get wired network connectivity for performance (2-3x wireless) and security reasons.

For advanced users familiar with rooting devices and flashing custom ROMS, the latest CyanogenMod builds should now have this fixed.

New Plugable USB 3.0 Universal Docking Station (with Dual Monitor Support)

We’re excited to announce the launch of our newest UD-3900 USB 3.0 Universal Laptop / Tablet docking station, adding an additional HDMI port to our UD-3000 docking station, currently the #1 selling Laptop Docking Station on Amazon.com.

Using DisplayLink’s top-of-the-line DL-3900 chipset, this unit offers all the functionality the DisplayLink chip has to offer, plus the latest VL812 USB 3.0 hub chipset from Via Labs for extra available USB ports.

Here are the two models side-by-side

Plugable UD-3000 Plugable UD-3900
$99.99 $129
New!

We’re excited to add this integrated, more cost-effective option for getting two extra displays (plus lots of other functions), all via a single USB 3.0 cable.

For both of these models, support is currently for Windows only. DisplayLink has new Mac drivers version 2.1 coming in future weeks which will allow us to update our recommendation for Mac.

And if you have any questions at all, please feel free to comment below or email us at support@plugable.com – we’re happy to help. Thanks!

Where to Buy

Plugable UD-3900 USB 3.0 SuperSpeed Universal Docking Station with Dual Video Outputs for Windows 8.... Product Details
$99.00

Plugable UD-3000 USB 3.0 SuperSpeed Universal Docking Station for Windows 8.1, 8, 7, XP (HDMI and DV... Product Details
$89.00

Plugable's Testing Station for Charging Behavior

The State of USB Charging

The humble Universal Serial Bus, more commonly known as USB has evolved to be much more than just a way to connect a mouse or keyboard to your computer. With the proliferation of power hungry portable devices that charge over USB, we’ve all come to expect USB to operate as a Universal Source of Battery charging, but unfortunately it’s just not that easy.

The original USB 2.0 specification limited the power that could be drawn from any USB port to 500mA. This is plenty to charge smaller batteries reasonably quickly, but for larger batteries a higher power solution is needed. This has driven device makers to come up with novel ways to draw more than the allowed 500mA from USB 2.0 ports and in general has been accomplished by the USB port signaling to the devices that it’s ok for the device to draw current at a higher rate.

Unfortunately there hasn’t been a widely adopted standard, so not all ports and devices speak the same language when it comes to charging. And, to make the situation even more frustrating for end users, there hasn’t been much public discussion or documentation about what has been done.

iPads for example, are one device that can charge at a very quick rate, up to 2.1Amps when connected to an Apple computer or Apple charger but they will potentially not charge at all when connected to a regular USB port. There’s also the BC 1.1 charging standard that some devices like the Kindle Fire or the Nexus 7 support, but that support is usually undocumented. We find out about charging behavior through trial and error.

So, try we did! We’ve been working hard to unravel the mysteries of what will charge where by testing every device we have on all of our hubs and chargers, and publishing this data on the product pages for each of our devices with USB ports.

We’re also collecting reports from end users though a quick form that let’s you add to the knowledge base of charging behavior.

Here’s what’s been added so far:
plugable.com/support/charging

To add your device visit:
plugable.com/support/charging-report

Check the FAQ on each of these pages for the details of our in-house test results.

Plugable Launches a New USB 3.0 Flash Card Reader

Tired of waiting for your photos to download? For photographers and other flash card users who want their files in a hurry, Plugable has introduced a new USB 3.0 flash card reader that combines blazing read speeds with the colorful design of our popular and well-reviewed USB 2.0 reader.

Plugable's new USB 3.0 card reader

How fast is it? As fast as your card allows it to be. In our testing with a newly-bought UHS-1 32GB SDHC card ($20 from Amazon), we saw read speeds over four times faster than our USB 2.0 device. Write speed improvements were in the range of 30 to 40 percent.

Results with less-advanced cards were throttled by inherent speed limitations of the cards themselves. Class-10 SDHC cards that were not UHS-1 clocked 15 to 20 percent gains in read speeds, while cards below Class 10 showed very little difference between USB 2.0 and USB 3.0.

So if you want to ensure the highest speeds from our new USB 3.0 flash card reader, make sure the card displays the UHS-1 logo. It makes a huge difference in your results.

Test results

Testing Platform: Windows 7 Pro 64-bit computer
Card: Sony 32GB SDHC Class 10 UHS-1 R40 Memory Card, purchased on Amazon for $20.
USB 2.0 reader: Plugable USB2-CARDRAM3
USB 3.0 reader: Plugable’s new USB3-FLASH3

Plugable USB 2.0 and USB 3.0 card  readers

Plugable USB 2.0 (top) and USB 3.0 (bottom) card readers

Photo test — 356 photos, 1.38 GB
USB 2.0 1:28 min
USB 3.0 28 seconds

Benchmark test using the Atto Disk Benchmark software
USB 2.0 Read 18 MB/s Write 16 MB/s
USB 3.0 Read 73 MB/s Write 21 MB/s

Benchmark results for USB 3.0 (left) and USB 2.0 (right)
130722_USB3.0_Card_reader 130722_USB2.0_Card_reader

For any questions, contact support@plugable.com.

Plugable SuperSpeed USB 3.0 Flash Memory Card Reader for Windows, Mac, Linux, and Certain Android Sy... Product Details
$12.50

USB hubs and chargers: What happens when you pull too much power?

USB power and charging issues are surprisingly complex. It’s natural to assume that hubs “deliver” a certain amount of power to a device. But that’s not really how it works. Devices can pull as much power as they want, but there are consequences. Devices are supposed to follow certain rules, like pulling no more than 100mA unless they configure up to a higher amperage (500mA for USB 2.0 and 900mA for USB 3.0). This is to avoid voltage drops which might knock other devices off the bus. Hubs and chargers are supposed to fail gracefully if a device pulls too much.

And it’s all gotten more confusing as USB has become a primary way of charging phones and tablets. There are many proprietary methods devices use to detect “their charger” and start pulling higher amperages. The USB-IF has a standard for doing this called the Battery Charging class, but the big guys like Apple, Samsung, and others don’t follow it universally.

So what happens when a device pulls more power than a hub or charger expects? What does a graceful or non-graceful failure look like? We wanted to know.

How we tested

To test what happens when a device draws too much power from a port, we needed a USB “device” that let us set the amount of power that it draws.  We came up with a box that uses large resistors to place a load on the USB power lines, simulating a device drawing power.  Instead of using the power to actually do something as a device would, our device simply dissipates it as heat.

Current-Tester

The box itself was designed in SketchUp and printed on a Printrbot 3D printer.

The red and black connectors are connected to the ground and +5V lines of the USB bus, and connected to a meter so that the bus voltage can be monitored.  Each of the switches at the top turns on one bank of resistors below.  Each set of resistors is chosen so that they draw 500 mA, 1 A, 2 A, and 4 A from a 5 volt supply.  By selecting different combinations of resistors, it can draw from 0.5 A all the way to 7.5 A in 500 mA steps.  Remember that the limit for USB 2.0 is only 0.5 amps–so we can pull up to 15 times more current than a host should be able to deliver.  This was on purpose.  We wanted to be able to take a hub and its power supply to the maximum, then a little further. Everyone here was really hoping for a fire (for better or worse, we weren’t able to create that much excitement even at the highest load).

Once connected to the device under test, the power draw was increased from 0 all the way to 7.5 amps, and the voltage recorded at each stop.  While it claims 7.5 amps, on every test we did, the actual current was less than 7.5 amps because the draw had caused the supply voltage to drop, reducing the current.

What We Found

Below are the test results from several of our devices.

UD-3000 USB 3.0 Docking Station

Power Supply Rating: 5V 4A

UD3000

UD-3000 Results

The UD-3000 has a 4A power adapter, and actively tries to prevent attached devices from affecting the core functions of the dock (graphics, network, audio). When the next step after the last one on this chart was turned on with the current tester, the port was disabled, and no longer delivered power until the load was removed.  The UD-3000 properly cut power to the offending port, and as a result, the DisplayLink device and other USB ports would continue to function in this situation.

Each USB port of the UD-3000 is equipped with a device called a polyfuse.  A polyfuse is a type of resettable fuse that automatically disconnects a power supply when too much power is drawn through the fuse.  When the load is removed, the fuse returns to its initial state.

While the polyfuse in the UD-3000 device was the one that cut power to the device, the voltage drop before that happened was due to the voltage regulation in the AC power adapter.  While the voltage had dropped considerably before power was cut, it was not low enough to cause devices to disconnect, and was far more than any device should be able to draw.

USB2-HUB-AG7 7 Port USB 2.0 Hub

Power Supply Rating: 5V 3A

USB2-HUB7-PowerTest

This is an example of a device with USB ports that do not have polyfuses.  There is a direct connection from the AC adapter input, to the USB ports.  This means that devices can draw as much power as they want, without being shut off.  This is an obvious advantage, as it allows for the usage of devices like the Raspberry Pi that perform no power negotiation, and can draw upwards of 1.5A with devices connected to the Raspberry Pi.  You can read more about the USB2-HUB-AG7 with the Raspberry Pi here.

While it looks like the voltage was quite low at the end of the test–and it is–this is because we were drawing nearly double the rated current capacity of the AC adapter.  At its rated current (3A), the voltage was still high enough to prevent USB device disconnections.  Past its rated current, it did continue to function, but the voltage was too low for some devices to function properly, and may reduce the life of the AC adapter.

PS12-USB2 Surge Protector Charging Port

USB Output Rating: 5V 2.1A

PS12-USB2

PS12-USB2 Results

Our surge protector is another device that properly handles an overcurrent situation.  On the surge protector, it states “2.1A Shared” between the two USB ports.  The test data show that when the current draw is increased above ~2.3A, the surge protector cuts voltage in order to reduce the current draw.  The regulator on this device is “smarter” than a simple polyfuse, and tries to reduce voltage so that the device will still receive some power, if at a lower voltage.  The voltage regulator in this device also did the best job of maintaining the supply voltage at 5 volts under greater loads.

Questions? Comments? Feel free to comment below!