USB advice

[Carole]

My laptop only has 3 USB ports.

1. Guidecamera
2. Imaging camera
3. EQMod

I can't have extra USB ports added (already checked that out with PC world and there is no-where to put any).
I am considering getting an EFW but obviously this is going to need a USB port.

I tried the other week to add a USB hub so I could add a cabled mouse (while I was fine tuning the alignment).  I know for certain that the imaging camera did not want to run off the hub and I wasn't sure whether it would be wise to run guiding off it, so in the end ran EQMOd and the mouse off the hub.

As the EFW is only being used when none of the cameras are in action, does it sound feasible to run this off the hub?

As you know I am pretty useless with technical stuff when it comes to knowing how much power items need and likely IT problems, so would be grateful for your advice.

Don't really want to change my existing set up as it all works, I am used to it and it's just more money.

Currently using a manual filter wheel which works OK but does have some limitations.  

Thanks

Carole

[RobertM]

There's a bit more to USB hubs than meets the eye.  For a start there are powered and non powered of which I would only use a powered hub.  Secondly, some hubs have internal buffers that allow both USB2 and older devices to be plugged in without dragging all the communications down to the lowest speed (the vast majority do just that).

In short I have not had any problem using just one USB2 laptop port with a powered USB2 Hub that allows both low and high speed devices to share.

I used a DLink 7port USB2 powered hub without trouble for quite a number of years but even all their hubs aren't good enough.  At the moment I'm using a Mount Hub Pro so the DLINK is a backup, as such you're welcome to try it out if you wish.

Robert

[Carole]

Thanks for the offer Robert.  I should have said that my hub is powered.  I can't remember the make as it's out in the Obsy but I'll take a look later.

I just wondered whether some items may or may not be amenable for use on a hub.
Basically I don't want to buy an EFW and then find I can't get it running.

Thanks will check out the make of my powered hub.

Carole

[RobertM]

You should be able to plug all your devices into just one USB hub but whether it will work with your particular setup is another question.  The hub I have can fully power all seven outlets to 500mA but I think many are much lower powered.  Some devices also draw current when you wouldn't expect and yet others supply power due to voltage tolerances.  In the end you may end up just trying it out to see if it works.

These are based on my experiences and may not be much help but it at least gives you some info.

Robert

[Carole]

Thanks Robert. 

Carole

[Ian]

I would think the best thing to do is to plug each camera into it's own port on the laptop and then everything else into a hub. A camera's going to use pretty much all the bandwidth available. EQMOD I would think should play nice with other usb devices like an EFW and a mouse.

[Carole]

Thanks Ian, that was what I was thinking.

Carole

[RobertM]

I never saw that being a problem Ian.

Carole, label all the ports.

[Carole]

I know which goes into what port on the laptop, but you are right I need to label the Hub ports, especially as that can get turned upside down. 

Carole

[The Thing]

Hi Carol,

I use a ten meter USB2 powered hub/extender with four ports (from Lindy,com). It has always run everything. At present 1x USB/serial, 1x USB/TTL (EQDIR equiv.), QHY5L-II Mono for guiding and 1000D. I have used it with a second hub chained for extra serial ports. The only thing I have found is that if I want high frame rates from the QHY for planetary imaging I need a seperate cable.

[Ian]

I never saw that being a problem Ian.

Carole, label all the ports.

it's not necessarily a problem, but generally each port into the laptop has it's own root hub internally so they each have access to the full bandwidth of the port. Each camera will use all the available bandwidth when it's downloading an image so either the download takes longer for one or more devices, or smaller, time sensitive data arrives late while it waits for the bus to become free like guiding or positioning info.

To be honest, I'm only applying my networking experience in general but USB is a shared access bus. If you can give your bandwidth intensive devices a whole bus to itself you're utilizing your resources most effectively. YMMV

[RobertM]

Yes but USB2 should be able to sustain 30-40MB/s so I'm doubting that it would cause any problems plus that bandwidth is shared to prevent device hogging.  If there's a hub between the device and the PC then there will be short synchronisation delays which make it less suitable for web cam type traffic such as high frame rate cameras; this is especially true if other devices are on the same hub... as you mentioned YMMV

[Carole]

So in summary - have I got this right?

If I use the 2 PC USB ports from my imaging and guide cameras and the 3rd port for my powered hub (EQMOd/ EFW/ mouse if required) it sounds like it is probably going to be OK, and if my hub isn't up to it there will be something that is. 

Thanks for all your help guys.  Haven't ordered the EFW yet, wanted to get some reassurance first.

Carole

[MarkS]

I always give EQMOD it's own USB.  If you run it via a hub and something goes wrong then EQMOD can freeze leaving the mount still doing whatever the last command to the mount was.  This happened to me mid-slew leaving me unable to halt a fast slew.  Luckily I was in the obsy and managed to rip the power lead from the mount.  If I had been doing it remotely, the result would have not been pretty.

If a guide camera freezes up because of a hub problem you'll only lose an imaging run.

The imaging camera, mouse and EFW are not in constant use and are not so critical so I would put those on the hub.

[Carole]

My imaging camera did not like it at all when I put it on the hub.

Thinks it's best then to stick with what I have.

The manual filter wheel can't wrong, it's just more faff to have to keep going out to change the wheel, and also I am forced to do flats at night because of light leak (Until I can find an efficient way of keeping the light out).  Plus the wheels only hold 4 filters, so I have to have a separate one for LRGB and NB. 

Carole