USB 2.0 over longer distances

Jun 15, 2005 4 Replies
C

One of the major requirements for an inspection camera I'm designing is that it needs to be connected upto



15 meters (45ft) away from the host PC. From the integration point of view I'd like to use USB2.0 to connect the camera to the PC. The speed is ample, hardware is simple (just one chip) and software is quite managable too. But it looks like I can't bridge 15 meters without using active repeater cables and since the cable will be moved back and forthconstantly, this is not realy a feasible option.

My question is, if the cable length can be extended to 15 meters by using a better standard cable or by using some extra line driver hardware (when maximum speed will be around 200Mbit).



Antoon


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P

Define inspection? That is a very wide field from object present or not through bar code type work and measurements to complete orientation with colour analysis. Each has different requirements and I wonder what resolution you have with the USB camera, compared to the inspection accuracy you require.

So if USB is not practical or meant for that type of distance (even with repeater cables you can get problems of reduced speed in some circumstances) the big question is WHY are you trying to do USB?

Consider using a better method of overcoming the distance, which all depends on your application as to resolution of the camera and how many images a second you can acquire and process. Let alone what is available for powering the device and capabilities of the host.

Unless the camera is very close to the host I would never even consider USB, and then for inspection or other analysis work only for SLOW capture frequency of 2 pictures/second or SLOWER.

Paul Carpenter | paul@pcserviceselectronics.co.uk PC Services GNU H8 & mailing list info For those web sites you hate
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M

Use an analogue camera, with 75 ohm coax, 100m would not be a problem. Have the AD video converter near the computer

martin

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H

No. USB will not work on cables considerably longer than the specced

5 meters. It may already take a bit of luck (i.e.: quality cables) to reach those 5. The problem is not signal strength either, but timing, so stronger drivers won't do you any good at all. You *need* repeaters to go beyond the limit.

Summing it up: forget about USB, use a proper video cable.

Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de) Even if all the snow were burnt, ashes would remain.
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K

I've seen cables with built in tranceivers which allow extended distances. Its possible to chain several of these together.

Ken

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