Maximum length of USB cables to control a camera is 50+m !

[Hibou]

In an earlier post about remote control of USB cameras via WiFi I suggested that active USB cables would be a simpler solution.

I have now obtained a batch of Delock 10m cables from Amazon and find that I can operate both SX Lodestar-X2 and Atik 414EX USB cameras over a distance of 50+ meters ! This was tested under Win-7 on an old Acer Aspire (Atom CPU) and under Win-10 on a modern Intel NUC (i5 CPU); both Nebulosity and StarLight Live (for the lodestar) worked fine. I didn't even need to use an externally powered hub for the Lodestar, since the USB power was still sufficient; of course the cooled Atik camera required a 12V supply.

The 5 chained hubs limit is imposed by USB, and Windows tells you that when you try to add a 6th cable. So 50+ meters over USB works, and maybe with 15m cables you could go even further. Timing does not seem a problem with these relatively low data-rate cameras.

[stash_old]

Its not quite that simple - e.g. some 7 port hubs are in fact 2 hubs and therefore leave only three more . Secondly not all cable is the same and so std electronics rules applies - power loss over distance and size of cable. thirdly the "standards" are followed by all Hub or cable makers.

I use single active 20M usb cables plus a hub at both ends (the further is powered) and all devices work. Take the power from the remote hub and bang I lose 1 device (Canon Camera).

The bottom line is - if it works for you great - but just dont expect it to be universal 

[Hibou]

33 minutes ago, stash_old said:

Its not quite that simple - e.g. some 7 port hubs are in fact 2 hubs and therefore leave only three more .

Perhaps, but I'm talking about active cables, not multi-port hubs. But yes, if  you don't have enough power,  you can use an externally powered hub - as the last link only. The length of the cable is limited by the transmission time required for two-way communication rather than power loss. So 5 chained cables, the USB limit for Windows, will work in general, provided very high data rates are not required. I did try lots of computers, operating systems and different cameras, and it worked every time with 5x good 10m cables.

It is however essential to plug in the active cables and wait for Windows to load drivers for them, before plugging in the camera, and again wait for the camera driver to be loaded. Windows loads a driver for each of the active cables in the chain in succession.

[Physopto]

Yes, the limit of 5 hubs?

Came across that on Friday night. I wanted a bit more length from the scope to the house, so I added another active cable. At first I could not get the computer to see the Com ports, even when all had worked previously. As I had just reconnected every thing I suspected I had missed a connection at first. Then whilst adjusting various things it gave intermittent connections, then a note from win 7 saying the maximum number of hubs had been exceeded. So I removed one active USB cable and everything worked, (I normally only use one).

I have three Lindy active powered 4 port USB hubs at the scope end and one active cable going to the scope. The simple fix was to use a none active extension cable of only 3 metres between the active cable and hubs.

USB can be a right pain in the rear end. When it fist was announced we were told you could daisy chain up to 128 devices. In practice I doubt you could.

I prefer to use cat 5 cable and a Belkin hub, but the cat cable is very easily damaged. I may now change over to USB to network adapters and use armoured cable, as I use it where it can be stood on.

Derek

[stash_old]

1 hour ago, Hibou said:

Perhaps, but I'm talking about active cables, not multi-port hubs. But yes, if  you don't have enough power,  you can use an externally powered hub - as the last link only. The length of the cable is limited by the transmission time required for two-way communication rather than power loss. So 5 chained cables, the USB limit for Windows, will work in general, provided very high data rates are not required. I did try lots of computers, operating systems and different cameras, and it worked every time with 5x good 10m cables.

It is however essential to plug in the active cables and wait for Windows to load drivers for them, before plugging in the camera, and again wait for the camera driver to be loaded. Windows loads a driver for each of the active cables in the chain in succession.

You are correct about the signal times however and I quote from the USB ORG " Active extension cables violate the USB Specification since they do not allow for proper bus topology management. A one-port hub integrated into the end of a 26ns cable is legal, and fulfils the same role without raising the possibility of violating power distribution and turnaround time requirements. The hub must be a bus-powered hub unless a power supply is used to meet the requirements for a self powered USB port."

Using Active Repeater cables is the same as daisy chainng hubs as each active cable extention is counted towards the magical 5 limit. So 2 active cables and 2 Hubs would count as 4. So using 5 active cables ifs the limit - in theory.

So while it works for you if you are keeping to a standard then stacking active cables may raise other issues. I am not saying you are wrong just trying to point out that what might work for you may not for other people,in their setup, even though you have tested "lots" of computers and kit combo's. A warning to other people to be aware and take it as read it will always work.

As USB Org have stated using Ethernet,fibre or other "converters"  usb will work over  kilometers but i would ask ,in the case of Astro , would you want to do that (in the UK).

Again if it works for you great and if others want to try this route do so but bear in mind the USB standard.

[andrewluck]

Another downside is all those unreliable USB connectors chained together. If you have a problem, which one is it!

There's no way I'd want those pulled through in the duct to my observatory.

Andrew

[Hibou]

2 hours ago, stash_old said:

...bear in mind the USB standard.

 

1 hour ago, andrewluck said:

There's no way I'd want those pulled through in the duct to my observatory.

If I had a 50m observatory with cable ducts, I too would use ethernet, just as I do in my home. But for 10-20m USB is probably best since it can power cameras like the Loadstar directly (yes I do know about PoE). The USB-2 standard is 16 years old, and 5m was once the theoretical maximum just like 9600 b/s was for copper telephone cable. And sometimes you can't run cable, so I'm also interested in wireless. Horses for courses.

[andrewluck]

What hasn't changed in the last 16 years though is that the maximum cable length is still specified at 5m.

What happens over the years is that people discover that the standard can be 'pushed' over the original specification. The laws of physics haven't changed in this time, they're just working closer to the physical maximum. The risk in this is that the original specification will have allowed for tolerances in manufacture along with changes in temperature and everything else that affects the performance of electronic devices. By working outside of the specification you stand a higher chance of running into performance or reliability issues. The Maxim DL Yahoo group has loads of posts with people complaining about lock ups in the program. In pretty much every case, the root cause is traced to USB problems.

Sorry if this sounds a bit pedantic. Have I used cables over 5m in length; yes. Did it work; yes . Use whatever you have to get something to work. But, be aware of what you're doing. As you say - 'Horses for courses'.

Andrew

[Hibou]

14 minutes ago, andrewluck said:

The laws of physics haven't changed in this time, they're just working closer to the physical maximum.

As a physicist I would like you to define "physical maximum" Are you going to insist on no transmission errors ? If we don't allow corrections for errors, reflections and other interference then the physical maximum for DSL would still be 9600 b/s and not 24,000,000+ Same  for USB, ethernet, TV broadcasts... No, I wouldn't chain 5x10m usb cables either, but the fact that it does work shows that the "physical maximum" is now more like 50m than 5m, so I'm happy to back off a little to 10-20m. OK, if people are continually plugging/unplugging USB cables they will have more problems than with a normally fixed cable like ethernet. But versatility is a big advantage for USB... and for wireless.

[andrewluck]

Sorry, bad choice of words with 'physical maximum'.

The maximum specified distance for USB 2 is 5m per cable. So, you can chain 5x 1 port hubs to achieve 25m and still be within the specification. Increasing this distance can be achieved using things like low capacitance cabling but, the fact remains that you're operating outside of the design.

Neither of us would chain 5x 10m usb cables. From a reliability point of view it doesn't make sense when there are usually more suitable connection methods. My main criteria when selecting equipment is reliability. If my camera locks up 5 minutes after I've gone to bed then that's a clear night wasted and with those being in short supply I can't afford that .

Andrew

 

[stash_old]

I have,as previously stated, used a 20M usb active cable  with 2 USB hubs (one powered) for months with no problems(famous last words) - Agree with Hbou Wireless would be nice but my experiments with VirtualUSB over wired/wireless IP have been mixed and as you say Andrew a "stable" link is a must else you are wasting precious astro time (sadly lacking at the moment). So USB is not ideal but it works and is cost effective - £15 for a stable 20M active cable link a bargain. If Hibou is lucky enough to have a working system  with just one 20m active cable and no hubs great. 

[pyrasanth]

If you seek stability then there is only one way to go in my opinion get an Icron 4 port extender & move to the data to your telescope by Ethernet. I have had many cheap hubs with mixed results. The one I have now seems pretty good & not as many issues but definitely I will be going the Icron route when funds permit. 

[stash_old]

On 1/26/2016 at 11:48, pyrasanth said:

If you seek stability then there is only one way to go in my opinion get an Icron 4 port extender & move to the data to your telescope by Ethernet. I have had many cheap hubs with mixed results. The one I have now seems pretty good & not as many issues but definitely I will be going the Icron route when funds permit. 

Up to a point but £200 quid and "not as many issues" I could not justify that - its nearly 1/2 way to a Lodestar X2 - I think I will give that a miss as I don't need 100m+ but interesting just the same

[Physopto]

Some one needs to bring out a cheap, reliable working USB to network extender that is USB 3 as it's bidirectional (both ways at same time) unlike USB 2, one way only at a time. Also get rid of the ridiculous mini usb plugs and sockets. They are useless for use in the field as they are far too easily broken.

The Chinese will always beat them in the end, albeit after some wasted time, if they don't get ahead now.

Derek

[pyrasanth]

13 hours ago, stash_old said:

Up to a point but £200 quid and "not as many issues" I could not justify that - its nearly 1/2 way to a Lodestar X2 - I think I will give that a miss as I don't need 100m+ but interesting just the same

I see where this is going but you can have the best equipment in the world being let down by a £20.00 hub- my hub currently cost me about £40.00 and is independently power switched. I don't get problems with it but the previous cheaper hubs with the current extender cable were quite temperamental. I went through the pain of a potential beautiful nights photography ruined because my "Mickey Mouse" FleaBay hub failed- never again!

If you go the Icron route you will get NO issues at all created by the interface. The more expensive powered hubs can still present issues but certainly not as prevalent as the very cheapest usb hubs.

[prusling]

Maplin currently have an active 5m USB2 extender for £5 online only.  Seems like good value if it works. 

I have one on order to extend a 3m cable from my USB3 hub in the obsy.

Reviews seem generally positive so fingers crossed! 

[stash_old]

2 hours ago, pyrasanth said:

I see where this is going but you can have the best equipment in the world being let down by a £20.00 hub- my hub currently cost me about £40.00 and is independently power switched. I don't get problems with it but the previous cheaper hubs with the current extender cable were quite temperamental. I went through the pain of a potential beautiful nights photography ruined because my "Mickey Mouse" FleaBay hub failed- never again!

If you go the Icron route you will get NO issues at all created by the interface. The more expensive powered hubs can still present issues but certainly not as prevalent as the very cheapest usb hubs.

Touch wood my £7 powered hub and £15 20m usb cable have not let me down but there is a lot of truth in what you say.  

[pyrasanth]

16 hours ago, Physopto said:

Some one needs to bring out a cheap, reliable working USB to network extender that is USB 3 as it's bidirectional (both ways at same time) unlike USB 2, one way only at a time. Also get rid of the ridiculous mini usb plugs and sockets. They are useless for use in the field as they are far too easily broken.

The Chinese will always beat them in the end, albeit after some wasted time, if they don't get ahead now.

Derek

Cheap & reliable in the same sentence. That would be a rare occurrence sadly proven time after time you get what you pay for as corners are always being cut to bring the lowest price to the masses irrespective of the frustrations which occur when the device inevitably fails. The USB specification is very loose & many of the ports can't deliver power to the "agreed" standard. Generally powered hubs are more reliable but even those sometimes have ports not able to deliver the full power as per the USB specification- it really is a minefield ready to be stomped on!

[Physopto]

At least the Icron  type have a full sized USB input socket, not the stupidly unreliable mini USB socket as in the Startech one. trouble is the approx. £100 extra cost!

 

[Stub Mandrel]

I found a reference to some Texas instruments work that determined that at 2000 baud the practical limit for RS232 is 3,000 feet (~1km).

1 hour ago, Physopto said:

At least the Icron  type have a full sized USB input socket, not the stupidly unreliable mini USB socket as in the Startech one. trouble is the approx. £100 extra cost!

 

"The newer micro-USB receptacles are designed for a minimum rated lifetime of 10,000 cycles of insertion and removal between the receptacle and plug, compared to 1,500 for the standard USB and 5,000 for the mini-USB receptacle."

So mini is supposed to last three times as long as standard - not sure if these translate into real-world experience. Scary only to than 1,500 insertions for that regularly used socket on top of my PC...