Solved: USB bus stays powered after shutdown

**S4Per** · 04-13-2004, 05:35 PM

Hi All,
We had a thread on this the other day, and the solution I implemented is slightly different than the one that was proposed.

Problem: USB bus stays powered even after Opus shuts down computer, thereby draining the battery. Secondly - I needed to power my USB hub.

Solution: I have 6 USB ports on the Shuttle, but unfortunately the 4 on the back of the computer are integrated into the board. The two front ones are not, and therefore have a cable that connects the ports to the mobo. Here - we spliced in a relay for the two USB ports (splicing into the power lines) that is powered by the molex connector. So - power is supplied to the bus only when the hard drive (for example) is powered. In essence, as soon as the computer shuts down, so does power to the bus. The second relay is essentially the same, except that it's for the 5v line that runs from another molex connector to the USB hub. So - power is supplied to the hub only when the computer is on.

It's essentially like the solution that was drawn up on the other thread, but note that no diode's, and therefore no drop in voltage, were necessary to do this. It works like a charm.

Thanks for all of the help and suggestions.

-Per

**MSUC5Vette** · 04-14-2004, 06:05 PM

Just curious, why did you decide not to use the relay?

**S4Per** · 04-14-2004, 06:39 PM

Not sure what you mean. I used two relay's, but no diode's.

So, relay 1: from HD connector to 2 front USB ports (power down ports when computer shuts down), and
Relay 2: from HD connector to USB hub power (power down hub when computer shuts down).

-Per

**Ricky327** · 04-15-2004, 02:23 PM

S4Per read shchua post #31 on :

Looking for a creative solution: USB bus still powered after CPU is off

Its a protection diode and you do need it...theres no voltage lost concern in that.

You dont wanna risk damaging your PSU, HDD or anything thats connected to that relay coil...I did say dont miss that diode...and do connect it the right way.

Glad you got it working anyway.

**S4Per** · 04-15-2004, 02:28 PM

a-ha...thanks much for the pointer. looks like i'll need to get that in there. thanks again!

**UncleGeek** · 04-17-2004, 07:02 AM

Do you need BOTH 5V power sources? Would this work with using only one relay on either the hub external power supply or the 5v power off the motherboard USB connector feeding the hub? Thereby eliminating one or the other power source?

**S4Per** · 04-17-2004, 09:30 AM

I needed to do 2 things:
1. Make sure that when the computer is off, no power gets supplied to the bus, and
2. Make sure that when the computer is off, no power is being supplied to the 'external' power supply of the USB hub.

So - two different things, therefore 2 relays.

HTH,
Per

**MSUC5Vette** · 04-17-2004, 01:05 PM

Originally Posted by S4Per

I needed to do 2 things:
1. Make sure that when the computer is off, no power gets supplied to the bus, and
2. Make sure that when the computer is off, no power is being supplied to the 'external' power supply of the USB hub.

So - two different things, therefore 2 relays.

HTH,
Per

Others who are considering doing this may want to look for a DP (Double Pole) relay. In this application a DP would do the same job as two relays, but would save some wiring etc. You would connect the bus to one pole, and the PS to the other.

Is anyone doing anything similar to this to control the power to their monitor? This way if you wanted to have the screen on when the car is off, but the computer running, but not supply power to the monitor to save the battery you could.

**UncleGeek** · 04-17-2004, 01:24 PM

S4Per,
Do you HAVE to have two seperate sources for power and why?

MUSC5vette,
I currently use a relay to power up/down my LCD display.

**Ricky327** · 04-17-2004, 03:51 PM

http://www.maplin.co.uk/Search/results.asp?CartId=040417214534929&Level=1&Menu=18 &Name=Relays

As MSUC5Vette advised :

Yes use DPDT relays on the list and save a diode too