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USB Extenders?
Davej wrote:
On Feb 13, 11:20 am, Paul wrote: Mike Easter wrote: Davej wrote: Anyone tried using low-cost USB extenders? They use Cat5 cable. I am wondering if they could be used to place a webcam up high where a more interesting view would be available. This company makes and markets a family of such extenders and related products with their tech and has a faq about their products and invites questions about particular applications for the products they make. http://www.icron.com/products/usb/faq.php We extend USB up to 10km over fiber optic cabling with our USB extender products, and extend HD video up to 500m over Cat 5 cable with our KVM products. also Video, Audio, and USB 2.0 over one single cable 500 meter distance over Cat 5 cable (Fiber distances over inexpensive Cat 5) Uncompressed HD video and USB 2.0 over a single Cat 5 cable LAN connectivity Up to 1920 x 1200 video support The icron usb-2.0-ranger-2212 is $366, and pumps power to the other end. 100 meter reach. http://www.smartvm.com/icron-usb-2.0...-extender-hub-... The icron rover-2650 is $110 and is USB 1.1. http://www.l-com.com/productFamily.aspx?id=2183 There is a bit of a price difference to watch out for. If the price is really cheap, it could be USB 1.1. To pump 480 megabits per second through the Cat5, you probably wouldn't want to do that on one pair of wires. GbE Ethernet, pumps more than that through the wire, but uses 125MHz 5-level logic signals, carried on all four wire pairs. It means GbE Ethernet tried to keep the spectral content down, for reasons of crosstalk. (Crosstalk being an issue, if multiple Cat5 cables are pressed together with nylon cable ties.) Pushing 480 meg through a single pair, using ordinary logic levels, would be more challenging. Doing it for USB 1.1, might not be nearly as challenging. It would be interesting to see whether the Cat5 wire in each case, is specified to have all eight wires or not (to see whether they use all wire pairs or not). Paul Well, it is interesting that while I can google and find various inexpensive products which claim to extend USB 2.0 it is much more difficult to find such products on a respectable site such as NewEgg. Here is one on amazon, and although it is not the extra-long Cat5 type, there are some positive reviews regarding use with some webcams. http://www.amazon.com/PTC-Meters-Ext...ref=pd_vtp_e_5 Unfortunately, that is not a Cat5 style device. There are two kinds of USB extenders. The one on the Amazon page is a "Native" extender. The wires carry standard USB electrical signals at all times. The one in particular you have selected, could be one that "cheats". The USB spec says an active repeater can be up to 5 meters long. This is a non-cheating one, with one "lump". It is 5 meters long. http://www.newegg.com/Product/Produc...82E16812120087 This cable is 10 meters long, and nobody seems to notice an extra "lump" on this one. For that to work, the time of flight of the electrical signal, would need to be half of what it was on the previous one. I can't understand how this is possible. http://www.newegg.com/Product/Produc...82E16812156026 And this company, sells some different ones. You can connect four of their 5 meter products, four of their 10 meter products (one lump), two of their 20 meter products (two lumps each?), or use one of their 50 meter products (five lumps ?). Adding an active hub to the end of the 50 meter product would not work, so only a 100mA load could be put at the end of the cable (or, you could arrange to power the device yourself). http://www.vpi.us/usb-extender.html ******* To detect cheating, you look for "lumps" in the cable. The lump has a one port USB hub chip inside it. And that is used for regeneration of the signal (plus the usual hub thru-delay). In this example, the lumps do digital regeneration. If you had a program which listed the USB devices, each of the lumps would register as a "hub". USB USB USB USB Host ----- lump ------ lump ------ lump -------- device In the Amazon picture, I see a lump in the middle of the cable, plus a lump on the end. Since the cable is coiled up, I cannot determine if there are more lumps or not. It could be two 10 meter designs placed end to end, like the Sabrent one. The 5 meter limit on USB, is a time domain limit. It assumes a certain dielectric constant and time of flight. With an exotic dielectric, perhaps the distance can be changed a bit. But I doubt you could change things by a factor of four. And therefore, the cable in question is undoubtedly cheating by having multiple regenerators. The Cat5 solution, changes transmission methods, and gets the extra reach that way. I'm not sure how they manage to beat the latency requirement. USB Ethernet_over_cat5 USB Host ------ Cat5_Box -------------------- Cat5_Box -------- device You can buy 5 meter active repeater solutions, with one "lump" per cable. Since the regenerator is on the end of the cable, you can have 5 meters more of passive cable to the webcam. USB Host ------ lump ----X ---- Plug in another passive cable plus webcam, here The thing is, bus powered devices have a current limit on them, so once you start using extenders, you have a 100mA limit. This is not sufficient for any good USB webcams (ones with motors and autofocus). To solve that problem, you need an active hub down at the end. The active hub, has its own wall adapter. That changes the current limit on the active hub, to 500mA. USB USB USB USB Host ------ lump ----X ----- (passive cable) ----- Active_hub ------- webcam | 500mA | Wall adapter 5V @ 500mA or greater Now, the other detail, is the maximum number of hubs/regenerators, allowed between a host and a peripheral. And this is further complicated, by certain recent Intel Southbridges, where the idiots burned up a hub inside the Southbridge, cutting down the max number of repeater cables by one. http://www.usb.org/results?q=faq&sub...%2F home&ref= "I really need to put a USB device more than 30 meters away from my PC. What should I do? A: Build a USB bridge that acts as a USB device on one side and has a USB host controller at the other end. Use a long-haul signaling protocol like Ethernet or RS-485 in the middle. Using cables or short-haul fiber, you can get ranges upwards of a kilometer, though there's no reason why the long-haul link in the middle of the bridge couldn't be a pair of radio transceivers or satellite modems. Embedded host solutions capable of doing this already exist. Also, two PCs connected via USB Ethernet adapters are essentially a slave/slave version of this master/slave bridge." So that tells you, the max reach (according to the USB.org site) using regenerators, is 30 meters. If you want more than 30 meters, then it's the "Cat5 bridge" solution, which doesn't use USB to make the extra distance. If we use those "double-reach" native USB cables, it would seem we could hit 60 meters. To do the 30 meters, you'd need four repeater cables, two passive cables, an active hub with 5V power adapter, and the web cam. I'm drawing this, to match the 30 meter claim on USB.org. Host ----- lump ----- lump ----- lump ----- lump --------- active --------- webcam hub 500mA -------- -------- -------- -------- -------- ------- 5 meter 5 meter 5 meter 5 meter 5 meter up to 5 active active active active cable meter repeater repeater repeater repeater cable If you have the Intel chipset with an "internal" hub in the Southbridge, you have to remove one of the repeater cables, and the total reach is 25 meters instead of 30 meters. Note that this is a "feature" on recent chipsets. If you had a motherboard from the LGA775 era, chances are you could build out the full 30 meters. On AMD chipsets, they might not have done the same thing as Intel did, so they might be 30 meters as well. By comparison, the Cat5 bridge, doesn't have these limits. But may still have practical limits, if the device has its own response latency requirements (buffer overflow). So doing it this way, for $300 or so, removes the 25 meter or 30 meter limit, and takes you to 100 meters over copper. (And a lot further with a $900 fiber setup.) USB Ethernet_over_cat5 USB Host ------ Cat5_Box -------------------- Cat5_Box -------- device electrical signals There are a number of aspects of this question, I cannot adequately answer. Time of flight is proportional to SQRT(Er) and looking at some velocity factor values, I don't see a span of a factor of two, between the best and worst cable dielectrics. So I don't understand how they can make a 10 meter length with one regenerator on it. And on the Cat5 device case, if the left hand Cat5 box terminates the USB protocol, on behalf of the right hand end, aren't there going to be situations where that will foul up ? I can't claim to understand even half of the details here. What I can say, is reading the product reviews is important. I have seen cases, for the 5 meter products, where the product fails when you concatenate them. So check the reviews, and if you see lots of complaints, it could be the +5V and GND wires are too thin in the cable. HTH, Paul |
#12
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USB Extenders?
In the last episode of
m, John Doe said: DevilsPGD boogabooga crazyhat.net wrote: John Doe jdoe usenetlove.invalid said: Davej galt_57 hotmail.com wrote: Anyone tried using low-cost USB extenders? They use Cat5 cable. I am wondering if they could be used to place a webcam up high where a more interesting view would be available. Issues of extending cables include signal strength and noise. USB extenders or active repeaters largely solve the signal strength and noise problems by appearing as hubs and regenerating the signal. I can't tell for sure, but I had the impression he was talking about a simple unpowered extension cable. It depends on the unit he's looking at, I've seen some going both routes. What's the difference between your "extender" and your "active repeater"? The only difference I can guess is that your "extender" does not include a buffer. In that case, it would not regenerate the signal. Something labeled as an "extender" might be a passive cable or might be an active repeater (which is pretty much just a 1-port USB hub) -- It's always darkest before dawn. So if you're going to steal your neighbor's newspaper, that's the time to do it. |
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