USB 2.0 manual mechanical Switch

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Hi there, not sure if this is the right NG, I have a Q in regards to
computer electronics :-)

I am trying to put together a manual USB 2.0 switch, one output to four
inputs (or viceversa). I use:

One Female A USB connector PCB
Four Female B USB connectors PCB
One four-way three contact rotary switch make-before-break (from Jaycar
El'nics)

To test, I have wired just one output and the input to the switch. However
when I try to connect the USB printer through it, I get 'Unrecognized
device' on the PC and the printer does not work . WHY ?? This is purely a
four-way contact - well actually the USB grounds are tied together and only
+5V, Data A and Data B are switched.

So I wonder, why does it not work ? It is a dumb manual switch. Another
switch I bought that uses semicon switching and a touch button is claimed to
be USB 2 but the PC always says it is USB1.1. How does it realise it is USB
1.1, and how it knows that my connection is not good ? I have wired straight
thru and also tried to reverse the data connections, to no avail.

Any ideas pls ? Do I have to connect any capacitors etc somewhere in my
manual switch ? BTW the manual  switches you can buy are ugly and huge, but
basically the same; A rotary switch and many USB connectors. So what do i do
wrong ?

Many thanks



Re: USB 2.0 manual mechanical Switch



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You really want break before make, otherwise you will get data
colliding on the bus.

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Also, USB is fairly fussy about the condition of the data on the bus,
so you will need to keep everyting as short as possible. You are
gettting into an are that will more likely cause you greif rather than
success. Its pretty much the same reason as why your purchsed 2.0
switch will only run at 1.1

You would be honestly better off spending the money on a decent
quality unit that probably terminates the bus correctly when
switching.


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Re: USB 2.0 manual mechanical Switch


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Why manual? You can get 4 port USB 2.0 hub for around $15, I've seen
some at my local Woollies supermarket. You'll probably spend more on
parts...

Tom

Re: USB 2.0 manual mechanical Switch



AdvarP wrote:
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The USB bus operates at a high frequency and requires properly
terminates lines, and properly laid out PCB tracks etc.
If you add a switch you upset all this it may or may not work depending
on how careful you've been with your wiring.
USB1.1 is lower speed so you may get it to work for that, but USB2.0
would be much harder with a manual switch.

Why do you need a manual switch anyway?

Dave :)


Re: USB 2.0 manual mechanical Switch



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What is your application? Why do you want to switch manually when hubs
do it automatically?

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It says there's an unrecognised device connected because the drivers for the
printer aren't installed.

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USB hubs and other components are powered either by the +5V from the
USB port on your pc, or by another power supply inside your equipment,
ie printer. So, if you're switching the +5V, and data lines on and off with
a manual switch, you would be getting corrupt data from the USB device
because of the bouncing of the switch contacts.

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You've probably got the port connected to a USB1.1 port. Either that, or you
have connected to a USB2.0 port, and there is signal degradation so the
USB controller switches to a lower speed.

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Get yourself a USB hub. They are low cost, and are designed to switch data to
different devices as needed, without having messy manual switching.

Jaycar have the following hubs which they say comply with USB2.0
4 port XC-4824 @ $29.95
7 port XC-4823 @ $49.95

Then again, some of the computer shops will be likely to have cheaper hubs.


Re: USB 2.0 manual mechanical Switch



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Short the unused ones with a 10kohm resistor across the data and you should
see improvement.



Re: USB 2.0 manual mechanical Switch





Short the unused ones with a 10kohm resistor across the data and you should
see improvement.


***** Could someone explain how does one "short" anything with a 10k
resistor?

The mind boggles.

Brian Goldsmith.



Re: USB 2.0 manual mechanical Switch


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EASY !!
Just apply it across 66kv mains.

--

Cheers ......... Rheilly P

Where theres a will, I want to be in it.



Re: USB 2.0 manual mechanical Switch



. . .
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Cut one wire off the resistor.

Solder one end of the wire to one of the pins.

Solder the other end of the wire to the other pin you want to short.

Wrap the rest of the resistor carefully in tissue paper.

Chuck the wrapped resistor in the bin.


Andy Wood
snipped-for-privacy@trap.ozemail.com.au

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The same way you "short" something with a zero ohm resistor.

Dave :)


Re: USB 2.0 manual mechanical Switch



does one "short" anything with a 10k
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The same way you "short" something with a zero ohm resistor.

Dave :)

***Ha ha!!!! :-)

If it is Zero Ohms,it has NO resistance therefore it cannot be called a
"Resistor".

Brian G.


Re: USB 2.0 manual mechanical Switch


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Yet one can buy a "zero ohm resistor"
http://au.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU50%8792

Even a zero ohm resistor has *some* resistance. So when you "short"
something you are actually just using a very low value resistance.

Dave :)


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how

Yet, as I'm sure you know, they're not an uncommon component, and supplied
by most, if not all manufacturers of resistors.





Re: USB 2.0 manual mechanical Switch


to keyboard and composed:

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They even come with a datasheet.

For example, here's a datasheet for a Vishay zero ohm (metal film?)
resistor:
http://www.ortodoxism.ro/datasheets/vishay/frj5055.pdf

The maximum resistance is 10 milliohm, and the max current is 25A at
25 degC and zero amps at 150 degC.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Re: USB 2.0 manual mechanical Switch



. . .

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So at 150 degC you have a zero amp zero ohm resistor. Maybe you can
use it as a zero amp fuse?


Andy Wood
snipped-for-privacy@trap.ozemail.com.au

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6 watts - crikey!

Dave :)


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. . .

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How can that be the same? You would need a zero ohm 10k resistor. Try
asking for one of those at DSE - you could get an interesting
reaction.

Andy Wood
snipped-for-privacy@trap.ozemail.com.au

Re: USB 2.0 manual mechanical Switch



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I get an interesting reaction when I ask for most things I want from DSE :-)

I saw zero ohm resistors in the mid 70's, used on DEC PDP/11 computer
boards. Yes, it was simply a shorting link, but an offical part with a
part number.

Used for board configuration, much the same as you now use shorting
blocks (or links) and header pins to hardware select drive config for
instance.

Don...


--
Don McKenzie
E-Mail Contact Page:               http://www.dontronics.com/e-mail.html

We've slightly trimmed the long signature. Click to see the full one.
Re: USB 2.0 manual mechanical Switch


Hi, many thanks for all the answers :-)

I need a USB switch for the following reason:

I have a 2PC network. I have bought a Canon PIXMA MP760 Multifunction which
is USB2 but not network enabled. I have avoided the HP network-enabled
multifunction (because I heard its s'ware was terrible - anyway, now I may
regret that a bit).

I have now got a D-Link router with USB print server. Thius works great for
pirnting but NOT for scanning or mem card reading.

So to be able to scan from both machines, I need to shift the USB cable from
one to another. I do NOT believe I can use a USB hub - can I really ? That
would be nice, I have not tried - so i would connect the input to the hub
tio the printer and the outputs to the 2 PCs ? I do not think this would
work. - hmm

Anyway, the 'manual' switch comprises the *break before make* (sorry I got
it wrong first time) rotary, 3 way 4 positions and the connectors.

In the meantime I also got the wizz-bang ATEN US-421 4 port USB2 switch.
Well this one has all the features including hotkey switchign and software
switching and you name it, BUT one of the PCs still cannot scan. Scanning
stops and I get 'connection lost'. The other PC has no probs. Both use PCI
USB cards so I am lost as to the cause of the prob - but that is off topic I
guess.

So the answer is NO because USB2.0 needs proper 'termination' ? Meaning what
? a 10k resistor from Data A to Data B on each port EXCEPT the one being
switched on ? That is a bit hard to do with the rotary.

In the end if I did get the HP I did not need all this. The HP also works
wirelessly I understand, so the wire crossing the room would not be there.
Ughhh. On the other hand there is a new Canon wireless printer available now
!

Many thanks



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----- Original Message -----
Newsgroups: aus.electronics
Sent: Monday, July 10, 2006 11:20 PM
Subject: USB 2.0 manual mechanical Switch


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Re: USB 2.0 manual mechanical Switch



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<snip>!
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Jaycar have a share switch, which may be what you require.

XC-4862 @ $59.95

http://www1.jaycar.com.au /

It allows 2 pcs to communicate with up to 4 USB devices, and is USB 2.0
compliant.


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