The Maximum Length of USB Cables

[leon]

Hi To All.

I was just wondering about extension USB cables, as i was considering to use a couple of extension cables so that i may be able to relocate the Lappy when using it for imaging.

To run the set up i use three normal length cables, one for the image download, one for the Toucan guiding camera, and also one for the USB box thingy.

At the moment they are all operating fine with no drop outs etc, however i wish to extend the cables some 5 meters, would this effect the performance of the components they are running, or would this extension be OK, would i need a booster of some sort to keep the signal strong.

If anyone can help with this please let me know.

Leon

[g__day (Matthew)]

Leon,

USB2 cabling can extend to a maximum of 25 metres by using 5 lots of 5m USB2 cable - but only if its

1) the type that have inbuilt repeaters and
2) so long as the terminating device has normal / low current demands

Whereas a normal 5 metre USB cable is $20 - a cable plus repeater (which is the size of a cigarette lighter at the end of the cable) costs between $30 - $50 (Jaycar are the cheapest)

Secondly a device like say a Meade DSI needs alot of current - more than normal USB 2 cable supplies - so they use a 25 gauage (vs 16 gauge) 2 metre cable.

The solution for this type of situation is run 25 metres of repeater based cable into a cheap A/C powered hub, and run the 2 metre heavy gauge cable from the hub to the imaging device. A normal unpowered hub won't do it!

[rogerg (Roger)]

I run my portable setup using 5m USB extension leads. Before I got my external power supply cable for my 350D I found that if the battery in the camera was anything much less than full, there would be some drop-outs (connection loss, files come back zero size, etc). I think it's related to cable length, temperature (cold nights) and the canon battery strength.

I don't have the problem anymore as I power the 350D from my 12v SLA.

Something I'd considered doing was just having 1 USB extension between laptop and telescope, a hub at the telescope, then short leads to the devices. I would make the hub a powered hub so that it's got plenty of grunt. Pretty much any hub could be run from a 12v SLA with some voltage converter thrown in to get to the 5v or whatever they require.

I would have gone down the line of having an intermediatory hub in the first place if my devices didn't grow one by one over time, slowly leading to more cables.

Roger

[ballaratdragons (Ken)]

Leon,

My modded Toucam runs happily with 7m of normal USB cable (1m on the camera, 5m extension, the 1m in the control room).

Whereas the DSI (as finally discovered) needs a Booster 5m cable (repeater cable as mention by g_day). I got mine from Officeworks Ballarat for $20.

[leon]

Thanks Guys for your advice, now Ken i actually have been to Office Works about three times in the last month, and still they don't have any stock, Might give Jaycar a try i think.

Leon

[ballaratdragons (Ken)]

Originally Posted by leon

Thanks Guys for your advice, now Ken i actually have been to Office Works about three times in the last month, and still they don't have any stock, Might give Jaycar a try i think.

Leon

Yeah, Jaycar is worth a try.

Also don't forget there is a Wiltronics Electronics store in Ballarat (5334 2513) up on Ring Road. He is often cheaper than all the others! Wiltonics is the place that made my 10m GoTo extension cable for $8.

[leon]

Good one mate,forgot about that place.

Leon

[turbo_pascale (Rob)]

There are USB<-Ethernet CAT5->USB cables/adapters around allowing you to go quite a lot further (50m to 100m), but I don't know how they will go power wise for the current draw.

Here's one I googled: http://www.lindy.com/uk/productfolde...2801/index.php

Note that these are USB 1.1 cables so might not be good for all purposes.

Turbo

[g__day (Matthew)]

They won't help much if you can't recognise the device at the other end to load the USB driver for. Whilst they sound a great idea - I tried them and couldn't make them work with the Meade DSI (and I have 20+ years experience with PC's from building, tuning to configuring systems - stumped me!)

[h0ughy (David)]

Originally Posted by rogerg

..................................
Something I'd considered doing was just having 1 USB extension between laptop and telescope, a hub at the telescope, then short leads to the devices. I would make the hub a powered hub so that it's got plenty of grunt.

................................

Roger

thats how Paul (1ponders ) does his, nice idea to copy.

[[1ponders] (Paul)]

It's actually quite embarassing now as I have two USB 2 hubs connected to the laptop

But they are for operating 2 setups

[rogerg (Roger)]

For quite a while I didn't have problems using my 350D over 5m USB extension leads, and I thought it went away when I started powering the 350D from my SLA, but on the weekend just gone at astro camp the problem reared it's ugly head big time.

I ended up borrowing a USB 1 5m cable with reapeater from someone else at the camp, solved my problem.

I'm now going to take drastic action:
- ditch the 5m cables i have except for one
- put a 4 port hub at the scope, with the one remaining 5m cord to the laptop
- use a powered hub
- build a 12v - 5v box and power the hub from the SLA.

My understanding is that a powered hub is as good or better than an unpowered repeater so should be good.

Now I just need to find the coolest looking USB hub to match the style and class of the GM8

So in summary, I would recommend not using 5m unpowered/un-repeated SUB cables for DSLR's. Seem fine for webcam, RS232, etc.

Roger.

[ballaratdragons (Ken)]

For my DSI-c I have to run a 5v Powered Hub AND a repeater booster USB cable. If I don't, she no work!

It's only 7m travel. DSI's really suck the power!!!

[mill (Martin)]

I am running an 5m usb2 cable with the dsi cable and have no problems whatsoever, this is the silver coloured usb cable from jaycar.
The only thing is, i run it from my normal computer and not from an laptop (could be an laptop issue).