Maximum cable length for USB ??
18 October 2003, 08:03 AM
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I'm thinking of putting up a security camera, well, web cam in a waterproof box....
Trouble is the Garage is at the other end of the house (approx 30m away)
Can the camera be connected to the pc over this length via USB. ?
Andy
Trouble is the Garage is at the other end of the house (approx 30m away)
Can the camera be connected to the pc over this length via USB. ?
Andy
18 October 2003, 11:27 AM
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From what I have seen looks like the max is 15ft.
You can however extend this with a line extender to 150ft.
You can however extend this with a line extender to 150ft.
19 October 2003, 03:49 PM
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From usb.org: http://www.usb.org/faq/ans5#q3.
Q2: Why can't I use a cable longer than 3 or 5m?
A2: USB's electrical design doesn't allow it. When USB was designed, a decision was made to handle the propagation of electromagnetic fields on USB data lines in a way that limited the maximum length of a USB cable to something in the range of 4m. This method has a number of advantages and, since USB is intended for a desktop environment, the range limitations were deemed acceptable. If you're familiar with transmission line theory and want more detail on this topic, take a look at the USB signals section of the developers FAQ.
Q3: How far away from a PC can I put a USB device?
A3: With the maximum of 5 hubs connected with 5m cables and a 5m cable going to your full speed device, this will give you 30m of cable (see section 7.1.19 for details). With a low speed device, you will be able to get a range up to 27m, depending on how long the device's cable is. With a straightforward cable route, you will probably be able to reach out 25m or so from the PC.
Q4: I need to put a USB device X distance from my PC. What do I do?
A4: If X is less than 25m or so (see previous question), buy a bunch of hubs and connect them serially with 5m cables. If you need to go farther than that, put another PC, or maybe a laptop, out where you need the device to be and network it with the first PC using something that's intended to be a long-range connection, such as Ethernet or RS-485. If you need to use nothing but USB, consider using USB based Ethernet adapters to hook the PCs together.
Edited to add: that; the hubs mentioned above need to be the powered variety. If you must use a PC based camera then a network webcam might be the solution. A cheap mono camera (colour can't see in the dark) linked to a simple video sender and a basic tv / capture card in your pc will probably be better in every respect and cheaper too. Unless you intend to view your (now empty) garage remotely via a webcam site then I'd consider making a regular camera cordless and adding a remote VCR starter.
Hope this helps
Simon
[Edited by GC8 - 10/19/2003 3:58:49 PM]
Q2: Why can't I use a cable longer than 3 or 5m?
A2: USB's electrical design doesn't allow it. When USB was designed, a decision was made to handle the propagation of electromagnetic fields on USB data lines in a way that limited the maximum length of a USB cable to something in the range of 4m. This method has a number of advantages and, since USB is intended for a desktop environment, the range limitations were deemed acceptable. If you're familiar with transmission line theory and want more detail on this topic, take a look at the USB signals section of the developers FAQ.
Q3: How far away from a PC can I put a USB device?
A3: With the maximum of 5 hubs connected with 5m cables and a 5m cable going to your full speed device, this will give you 30m of cable (see section 7.1.19 for details). With a low speed device, you will be able to get a range up to 27m, depending on how long the device's cable is. With a straightforward cable route, you will probably be able to reach out 25m or so from the PC.
Q4: I need to put a USB device X distance from my PC. What do I do?
A4: If X is less than 25m or so (see previous question), buy a bunch of hubs and connect them serially with 5m cables. If you need to go farther than that, put another PC, or maybe a laptop, out where you need the device to be and network it with the first PC using something that's intended to be a long-range connection, such as Ethernet or RS-485. If you need to use nothing but USB, consider using USB based Ethernet adapters to hook the PCs together.
Edited to add: that; the hubs mentioned above need to be the powered variety. If you must use a PC based camera then a network webcam might be the solution. A cheap mono camera (colour can't see in the dark) linked to a simple video sender and a basic tv / capture card in your pc will probably be better in every respect and cheaper too. Unless you intend to view your (now empty) garage remotely via a webcam site then I'd consider making a regular camera cordless and adding a remote VCR starter.
Hope this helps
Simon
[Edited by GC8 - 10/19/2003 3:58:49 PM]
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