[senit] power for trackerball plus

This is an interesting thread. We had a spate of compaints about 
rollerballs stopping working during lessons on desktop PC's. Sometimes 
plugging it into a different USB socket (at the front or back) worked. 
Not being in the classroom I didn't realise it was on the same PC until 
last week I was told the monitor had failed. On going to the class I 
plugged in a new mains lead and it worked. What was at fault was the 
'Y' power cable that powered the PC and the monitor. The PC kept 
running but the monitor didn't. Having now read this thread I'm 
begining to think the issues with the rollerballs was due to power 
fluctuations... but not being an electrician I'm no expert. Since 
changing the power lead the rollerballs have been fine!

----Original Message----
From: charlie.danger at googlemail.com
Date: 18/03/2007 12:30
To: <senit at lists.becta.org.uk>
Subj: Re: [senit] power for trackerball plus

Hmm... is the USB voltage getting lower in newer laptops?

USB is a very tight specification and the upstream voltage provided by 
the
sockets on your laptop has to be between 4.35 and 5.25V. USB devices, 
such
as the joysticks, must be happy with that range or they're not allowed 
to
have a USB plug on the end of them. Naughty naughty.

Maybe its an issue with power. The current provided by USB cards (i.e. 
the
sockets on the laptop) has to be 100mA but most USB cards can provide 
a
current up to 500mA. Windows will tell you how much power a device 
requires
and how much each socket is willing to provide:

www.bltt.org/hardware/usbpower.htm

How many joysticks have been suffering from this problem? And do they 
work
ok on older laptops or desktop PCs?

If it's true that the joysticks won't work lower in the voltage range 
then I
think traxsys probably have a duty to fix them. As Geoff points out 
it's
possible to boost the voltage using batteries but it's pretty 
impractical to
expect all joystick users to start doing this.

On 16/03/07, LONGEATONPMIS at aol.com <LONGEATONPMIS at aol.com> wrote:
>
>
> What about a battery powered hub. I don't expect mice take a great 
deal of
> current and you could use rechargeable 9v batteries and a bit of 
circuitry
> to
> make a stabilised 5v USB supply. Actually you wouldn't even need the 
hub,
> just
> a  feed through on the signals. You could have an LED for the 
battery
status
> but  the power for the LED could come from the computer.
>
> Just a thought.
>
> Geoff,
> LEPMIS.co.uk
>
>
> In a message dated 16/03/2007 11:43:16 GMT Standard Time, 
CENMAC4 at aol.com
> writes:
>
> Already  thought of that, but the issue is that the pupil is using 
it in a
> mainstream secondary school and would like to use it at his desk,
(not  near
> a
> socket) but may be the only  solution.
>
> Thanks
> Trish
>
>
>
>
>
>
>
>
>
>
> Long  Eaton Powered Mobility Integration Service
> Special Controls for Special People
> Integrated  Systems for an Integrated Life Style
> on the Web LEPMIS.co.uk e-mail Geoff at LEPMIS.co.uk
>
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Mandy Griffin
Senior ICT Technician
Southview School
T: 01376 503505
F: 01376 503460

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