- Apple Software
- Cables and USB Ports
- eReaders & USB Tablets
- Syncing Devices
- Universal Sync-Charge Hubs
- Universal USB Chargers
We are often asked if inexpensive USB hubs are good enough for charging and syncing a limited number of devices, especially given the difference in cost between a consumer device and a “professional” hub designed for institutional use. The answer is that some hubs may be good enough to handle two or three devices, but there are a number of issues that come up when more are connected.
We asked an outside engineering team to check out a 28-port hub called the Mondohub (by Manhattan), which is sold on Amazon, Best Buy and a number of web sites. They bought it from Amazon. It had been reviewed by gadget sites and it is very reasonably priced for what it claims to do.
Accompanied by some fascinating photos (which we are not posting), this is just an excerpt from what they reported. It is a good lesson in what to ask for in a hub, from the point of view of (a) performance, (b) reliability, and (c) safety.
We have done some testing on the Mondohub by Manhattan and can make the following comments. The tests are easily replicated and we can provide details on request.
- The unit is of cheap design and uses very low-cost connectors, a lot of which are ‘wonky’ and, bizarrely, dirty. This is not great for signal integrity and can also cause an increase in contact resistance which can, in turn, cause heating (I2R losses) in the connector itself.
- It has a CE marking but the unit (if used per the manual) has a case temperature significantly higher than what is legally allowed. It’s a burn/fire waiting to happen.
- The unit has a totally inadequate power supply rated at 5V/4Amp. It is inadequate because a USB2.0 port should provide a minimum of 500mA (0.5Amp) per port and a USB3.0 port should provide 900mA. Doing the math is quite simple: 24 USB2.0 ports multiplied by 0.5Amp is 12Amps. Four USB3.0 port multiplied by 0.9Amp is 3.6Amps. Add the two together and you get a minimum required current of 15.6Amps. In reality you will also need a couple of amps extra to run the hub electronics, etc. so let’s call it a nice round 18Amps required. This is way below the 4Amp which it offers.
- To be compliant with the USB spec, the VBUS voltage should be between 4.75V and 5.25V; i.e. 5V +/-5%. Under modest loading of a few iPads, this voltage falls way out of spec and gets close to 4.3V. This VBUS voltage continues to drop as more iPads are added until the iPads simply don’t acknowledge that they are connected to a USB port at all!
- The maximum number of iPads that can be used with this hub without running the supplied PSU outside its operating range (4Amp) is a theoretical eight. We say “theoretical” because, in reality, the PSU has no over-current protection until you draw much more current than this. We have “successfully” connected 12 iPads to the hub and had them all appear in iTunes/Configurator even though the PSU was running way out of its operating range. We know it was out of its operating range because the range is printed on the PSU. We also know this because the plastic case temperature reached 95 degrees C and its plastic started to become soft and deformed.
- Adding more than 12 iPads created a very unstable system due to the power supply voltage dropping down towards 4.2V and the power supply switching on and off occasionally as it toasted itself internally. The issues we saw with 14 iPads was that the power supply for the hub would become extremely and dangerously hot and VBUS would reduce. This then causes the iPads to disconnect. Once they disconnect, they draw a little less current and the VBUS voltage rises again. The iPads then reconnect and the cycle continues until the MacBook shuts down the USB port and requires a restart. No successful sync task could be performed with more than 12 iPads. When we say “successful”, what we mean is that a sync could be performed with the PSU running way out of spec, VBUS at a level where the iPad only just acknowledges connection and the PSU running at a temperature that could cause severe burns.
- After 30 minutes of use with 12 iPads, the PSU connector which connects into the hub becomes very, very hot and, on removal, the plastic/rubber overmold can be squidged flat with your fingers (if you are quick and can handle the heat!). Again, this is because the actual PCB connector receptacle is not rated at even 4Amps, let alone anything more.
- The internal PCB was very dirty and had lots of flux, splashes of solder and ‘gunk’ all over it. This could be purely cosmetic but it is something which gives an insight into their manufacturing facility.
- Although it says it does, the hub does not charge any devices which we have tried, although it may well charge small devices. This is subject to the same limitations as the number of iPads.
- To be used within the spec of the supplied PSU, no user should connect more than seven or eight iPads (2.1A or 2.4A) or USB devices (which require 500mA each). Failure to adhere to this number will exceed the maximum loading on the PSU and it then becomes a fire risk because there is no sensible protection.
- The USB ports have no over-current protection and the current available at the ports is at a level where it could be deemed a fire risk. As part of normal CE and UL testing, devices are supposed to prove adequate port protection.
- If a USB port is directly shorted out, it shuts off the whole PSU and board rather than a single port.
- The USB3.0 cable is directly attached to the hub and cannot be changed if damaged.
- The magnetic feet fell off the unit.
- The cable coming out of the PSU is rated at 80 degrees C and the cable reaches this temperature at the exit of the PSU. 16. The unit was shipped with a PSU which had a 2 pin shaver connector on it. Odd because this is not what one would normally need.
In summary, this product does not do what it says it can do (power 28 USB devices) and poses a serious risk to the equipment. It may be suitable for syncing seven or eight at a push but, for any more than this, you would risk damaging your equipment.
A The Kindle Fire HD and some of the earlier Kindle models can share the same Amazon account, permitting syncing of shared content1. Amazon assigns a unique PID and DRM licensing profile for each device associated with an account. When used with Datamation’s Universal Sync-and-Charge USB Hubs (DS-SC-U8, DS-SC-U16 or their equivalent in carts or cabinets), multiple Kindle Fire HD’s will be displayed under Amazon’s Device Management2 giving account owners the ability to download licensed (DRM) content (books, videos, magazines, subscriptions) and other files (such as PDFs, .DOC, .TXT). When used in sync mode, the Kindle Fire HD and some earlier models will not be getting a full charge because USB switches to 500mA per port in sync mode. Once the host computer is disconnected, all the Kindle Fire HD tablets will automatically switch into charge mode and the devices will be charged at the highest optimum level prescribed by Amazon.
For charge-only and security applications, Kindle Fire HDs can be used (using Amazon-provided cables) with Datamation’s DS-C-U8 or DS-C-U16 Universal hubs, which provide the optimum charging level for all connected devices. Datamation Universal Charging and sync charge hubs are available in cart, cabinet, safe and transport case configurati