power leaking through USB hub????

spiro · 01-02-2007, 08:46 AM

this is driving me grazy! I dont understand the connection!!!!

after I shut of the ignition, unless I cut external power to the USB hub or disconect the "OPUS" from the battery, the touch screen stays illuminated with a faint glow as if its "underpowered".
If I power another device through the ignition 12 v line it reduces the glow as if the two devices are sharing the power
Where is it coming from?
I initially had the LCD powered from the same 12V line as the hub (through the cars ignition switch), and I thought power was leaking backwards from the computer USB to the hub and to the LCD throught the Touch Screen controller (USB) but then I put the LCD power feed on a different line (still through the ignition switch) and there was no change
Strangelly when I disconnect the OPUS psu completelly from the battery the problem goes away!

I m looking for crazy answers because I went through all the logical explanations/scenarios....
Im thinking of bringing in an exorcist next.....

spiro · 01-02-2007, 08:56 AM

sorry here is the connections diagram!

strohj · 01-02-2007, 08:59 AM

unplug the USB connector on the screen to see if it is getting power that way...

the way you describe it.... you either have the opus wired weirdly and it is "leaking" current back.. or it is stilll giving power on the 5v line.. and your screen is somehow using that power to power up(albeit very faint)

spiro · 01-02-2007, 09:13 AM

the 5v line from the PSU definetelly has power (i didnt do the modification to the OPUS because I would have to send it back) but i dont see how it could be leaking back to the screen!

"unplug the USB connector on the screen to see if it is getting power that way..."

I was hoping not to have to do that but I will try it next (still doesnt solve the problem)
thanks

strohj · 01-02-2007, 09:16 AM

the 5v line should have power .. that way you can put your carpc in standby...

im just hoping that its not something with your screen that is screwy...

spiro · 01-02-2007, 10:36 AM

I ll let you know what happened after I unplug the screen USB connector...

I m gonna put a voltmeter on the USB lead coming from the PC to the screen to identify if there is voltage on IT after shutdown ,I think there is (in compliance with the MINI ATX architecture), but even if LILIPUT screwed up and somehow there is a connection between the USB TS and the rest of the cirquitry why is it that its visible on the screen ONLY when I feed power to another USB hub which is not even in the same circuit with it?