Why does this cable not work on my iMac?

[The.316]

Its a simple USB splitter. What I wanted to do is add my Logitech MX mouse and Logitech keyboard USBs to it. When I connect one of the two USBs to the port on the back of the iMac, it works fine, but nothing works when both are connected. I tried one of the two, with my HD webcam as well, and again, nothing works. I tried a different port, but again, nothing works. Is the power from the USB just not powerful enough?

I have all the USB ports taken up. I have the following connected:

-LG external Bluray drive
-A Belkin USB/firewire HUB that has my current wired keyboard connected
-Logitech c910 Webcam
-USB extension cable to the front of desk, to plug in thumb drives

This is what it looks like in System Report:

Also, I use to have a powered usb hub connected to the iMac, where the extension is now, but ever since I upgraded to Yosemite, the hub does not work. It will read a thumb drive, but would freeze my keyboard and MX mouse. If I tried to plug in my iPad or iPhone, it would not charge, and again, the keyboard and mouse would not work. Is too much power being used, or is there something else going on?

 

[YanniDepp]

Because USB devices send data up and down the cable. If you want more than one device in a USB port, you need a hub to control which data flows to and from each device. You can't just solder two data wires into the same connector like that.

I have no idea why that cable even exists. I've seen cables that feed two USB ports into one device (e.g. power for external hard drives), but never one that splits the other way.

 

[Julien]

Don't believe there is any such thing as a simple usb splitter like an audio cable splitter. The 'splitter' must have a USB controller chip in it. There may be some incompatibility or it may be defective.

 

[The.316]

Because USB devices send data up and down the cable. If you want more than one device in a USB port, you need a hub to control which data flows to and from each device. You can't just solder two data wires into the same connector like that.

I have no idea why that cable even exists. I've seen cables that feed two USB ports into one device (e.g. power for external hard drives), but never one that splits the other way.

Gotcha. But...why is the hub not working with the iMac? I had a generic one which didnt work, and I also have a Belkin one that does not work either. Its a simple 7 port hub that has its own power adaptor. I even tried using different USB cables, just to see if that was the problem. Is it because there are too many things in the USB ports already? If so, I can remove the Belkin USB/FW hub, since I do not use it that much anymore.

 

[Gav2k]

That cable is for power only like splitting a sub charger or one device and power to another.

 

[YanniDepp]

I can't think of any reason why a hub would stop working, let alone two hubs.

Sometimes I have issues with the USB ports on my Macs, where a port just won't see a device. It happens occasionally with every Mac I own. Unplugging it and plugging it into a different port usually works. I'd try swapping your USB ports around.

 

[The.316]

I can't think of any reason why a hub would stop working, let alone two hubs.

Sometimes I have issues with the USB ports on my Macs, where a port just won't see a device. It happens occasionally with every Mac I own. Unplugging it and plugging it into a different port usually works. I'd try swapping your USB ports around.

Should the USB hub still at least charge my iPhone or iPad? I tried plugging in the hubs to a power outlet in my kitchen, and I plugged my iPhone into it to see if it charged, and it didnt even do that. Do they work only when plugged into a USB port as well?