USB extensions, how far?

[viper150]

Hello,
I have researched this but i hope to get a difinitive answer here. It has been suggested that USB should only be extended 16 feet. Others claim as much as 36 feet. I extended a usb device nineteen feet, one ten foot and one six foot cord plus the three foot device usb cord. The device was originally equipped with a serial input and a usb adapter card was supplied with the machine. The device was working fine for several days but the usb adapter card failed. One of the tiny chips became very hot and there were signs of heat damage on the back of the pcb. The supplier has replaced the card and everything is working once again but i am now using a laptop with only the three foot device cord attached until i can verify that extending the usb could not have caused the failure. And that is my question. What are the consequences if any, of extending a usb device? Would it simply affect transfer rate or cause communication failures or could it actually cause the failure of circuits within the device? Any help would be greatly appreciated. It is truly a pain having to use a laptop near the device. Others have stated absolutely not, using extensions could never cause failure of the circuits, they could only cause performance issues. Are they correct?

 

[DelJo63]

The maximum length of a standard USB cable (for USB 2.0 or earlier) is 5.0 metres (16.4 ft). The primary reason for this limit is the maximum allowed round-trip delay of about 1,500 ns. If USB host commands are unanswered by the USB device within the allowed time, the host considers the command lost.

1394 Cable length is limited to 4.5 metres (14.8 ft), although up to 16 cables can be daisy chained using active repeaters; external hubs, or internal hubs are often present in FireWire equipment. The S400 standard limits any configuration's maximum cable length to 72 metres (236 ft). The 6-circuit connector is commonly found on desktop computers, and can supply the connected device with power.

Assuming you can afford them

Of course you an ignore those theoretical limits and may actually get away with it ; again assuming you're willing to live with corrupted data that may result.

 

[viper150]

Thanks for the info jobeard. Maybe my post was long winded but i wanted to clarify the problem i was having. My main question is whether or not pushing the limit of extending usb can actually damage circuit boards? As i stated, i extended mine 19 feet using three usb cords. A usb adapter card on my device failed. I have a new card installed and everything is working fine again but i want to be absolutely sure that the extensions had nothing to do with the failure of the card before re-connecting to the same computer. I realize that exceeding the limit might cause communication issues but again, my main question is whether doing so could actually fry a circuit board.