Powered USB Hubs

[Andy Wilson]

I’m in the process of setting up a new observatory. This is larger than my old one and so I’ve had no option but to go for 5 meter usb cables. Not too surprisingly I’ve been getting problems with my main and guide cameras loosing connection.

I understand the solution is to get a powered usb hub. I have a couple of questions on how to use these as I expect other BAA members have similar setups.

1 – Does it matter whether the hub is next to the computer or the telescope?

2 – Would I link both my main and guide cameras to the hub with a single cable linking to the computer? I’m guessing the hub has a single computer connection to multiple devices. So I’m not sure if I’d need separate hubs for high transfer rates to avoid putting too much data through a single usb.

I’m sure I could work this out by trial and error, but if anyone has any advice then that would be most helpful.

Thanks,

Andy

[Roy Hughes]

You are using 5m USB cables. Are these passive or active?

Several years ago I came across a 5m active USB 2.0 Extension cable in Poundland and at 1 pound it was was a no brainer to buy one in case I ever had a use for it. I never have.  

Ebay (try USB CABLE ACTIVE) has a large selection of them, one even claiming to be USB 3 and supporting 5Gbps data rate.

Might be an alternative, if they work!

Roy.

[Dominic Ford]

Roy is right.

5 metres is right at the limit of how far USB signals can travel without dispersion leading to an unacceptable error rate. So you really need to have something on the end of the cable acting as a repeater.

An active USB cable does exactly this: there’s a small repeater in the plug furthest from the computer. I’ve used cables like this and they seem to work.

I imagine that plugging the far end of a passive 5m cable into a powered (or even unpowered) hub would have the same effect, but I’ve not tried it.

[Martin Mobberley]

Hi Andy,

Back in 2003 I faced the same issue with my C14/Paramount/SBIG ST9XE system, some 35 metres from the indoors PC I wanted to use. The Paramount was controlled via a serial port in those days, and the JMI focuser was just voltage controlled. I simply extended the wires by 100 feet! However, the camera was USB 1.1 so that was the real problem…. I solved it by purchasing a USB extender manufactured by Icron and marketed by Scene Double. This consists of two boxes, named REX and LEX. LEX sits indoors by the PC and REX sits on the telescope plinth. The LEX box is powered, the REX is not. They are joined by a single Cat 5 cable under the lawn. There are 4 USB ports on the outdoor Icron REX so 4 USB inputs can be used, although I usually use just one. Of course, USB 1.1 is very slow these days, but, the system still works, after 12 years outdoors and with the outdoor REX box a bit rusty now! Icron still make these units and Scene-Double still sell them. They are not cheap, BUT, when something has worked flawlessly for 12 years, in all weathers, that’s pretty good. The current webpage can be found here, with USB 2 and 3 systems now:

http://www.scene-double.co.uk/USB-extenders/

Of course, you are just talking about a distance more than 5m, whereas my system is 35m, so you may not need such an expensive overkill solution, but, that’s the system that has proved reliable for me.

Martin

[Andy Wilson]

Roy, Dominic and Martin,

Thank you for your responses. I hadn’t realised you get get powered cables, which gives me another option.

Martin, the Cat 5 to usb solution is also interesting. Like you say probably overkill for what I need, but worth looking at in more detail if I can’t solve the problem with simple extenders or hubs.

Thanks,

Andy

[Dominic Ford]

Cat 5 cable is pretty amazing stuff. It’s built to carry very high data rates with minimal dispersion over long distances, and it works!

I know somebody who wanted to have a PC they could access in their shed and indoors. He wired the keyboard, mouse and SVGA data signals down 30 metres of CAT 5 cable buried under the lawn. Normally SVGA deteriorates even more than USB over long distances, but his set up worked perfectly.

Then again, I think he paid an arm and a leg for the connectors (impedence mismatches can be a nightmare if you bodge the cables together), so probably best to try a simpler solution first.

[Nick James]

Hi Andy,

Depending on what you are doing it may not be relevant here but I’ve always found it much better to put a cheap headless PC by the telescope pier. You can then connect all of the telescope/camera USB cables to this directly and remote desktop to it over a network from anywhere.

Nick.

[Callum Potter]

Another option is USB over Ethernet – i’ve not tried it but have been told it works well.. YMMV.

Callum

[Andy Wilson]

Dominic, Nick and Callum,

Some interesting ideas.

I’ve decided to opt for a middle of the road powered USB hub. If it doesn’t work then I’ve only spent £25. The computer is in the observatory at the moment, but I think 5m cables is just over the limit for stable usb camera connections. I’ll give some of the other suggestions a go if this doesn’t work.

I actually had 2 cat5 cables laid from the observatory to the house when I had the original observatory built. That gives me internet in the observatory, and also gives me the option to remotely control everything in future if I want to. However, they only go to the wall of the observatory, not to the pier.

Thanks,

Andy

[Paul Anthony Brierley]

Good morning Andy,

I use two x 5m active repeater USB cables, that go from my control room, via a mains powered USB hub. At the pier end. I use another 4 port hub, this is powered via a 12 volt portable supply, made for a sony play station.

I plug all my imaging gear and other equipment into this hub, and then control all, from the “Whirlpool Observatory”

The secret is. “HOT” glue the extension cales, to prevent moisture from causing drop outs. I also have all my USB cables Hot glued into position on my pier.

I and another imager from my society. Have never had any problems with loss of single.

[Andy Wilson]

Hi Paul,

Thanks for the advice. Your setup sounds not too disimilar to mine so it is good to hear that a powered USB hub and active cables worked for you.

I got things working with a powered hub for an observing run last weekend, and I am now waiting for another clear night to see if this really has fixed the problem. I’ve found everything just works fine in the daytime, it is only when I start proper night time observing that I get drop outs! From the sound of it powered USB cables will be the way to go if I still have problems.

Thanks,

Andy

[Mr Nicholas John Atkinson]

I have a USB hub which can handle multiple inputs in my case the filter wheel, main camera and guide camera. This feeds into a 5m cable that is connected to the lap top. Using Maxim DL; The Kenderick 12 volt USB hub provides connectivity and is powered by a Maplin Regulated Transformer. This also powers the dew controller and the mount Drive.

The planiterium software runs through a seperate cable to the mount

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