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

**yanksfan_98** · 04-14-2004, 12:42 PM

The people that wanted to use the HDD power to drive the relay to completely disconnect the OPUS are going to have a problem. The OPUS will never turn on until that relay gets 12v across it, which will never happen unless that relay is closed.

There might be other ways to devise a switch, but that aint it.

Sorry.

**Laidback** · 04-14-2004, 12:53 PM

Originally Posted by yanksfan_98

The people that wanted to use the HDD power to drive the relay to completely disconnect the OPUS are going to have a problem. The OPUS will never turn on until that relay gets 12v across it, which will never happen unless that relay is closed.

Sorry.

Then you activate the relay from two different sources.

**MSUC5Vette** · 04-14-2004, 07:01 PM

Originally Posted by Laidback

Then you activate the relay from two different sources.

My understanding was that you would run the relay 12v output parallel with the ignition trigger. When the ignition is triggered it will turn on the opus, and opus will close the relay, completing the power loop even when the ignition is removed.

I would highly suggest using the HDD connector to power the relay, even if it is a low current relay, simply because the HDD connector is designed for high current applications (ie spinning the HD motor) as was mentioned above, the PS/2 port is probably not a high current output device.

**MSUC5Vette** · 04-14-2004, 07:03 PM

Just in case anyone is looking to do this with an inverter, I wired up a relay on the HDD output accross the on/off switch of my inverter to do basically the same thing. I also put a relay accross it which was triggered by the ignition in the on position. My old MB automatically booted when power was supplied, so this worked well as an auto on feature.

**Ricky327** · 04-15-2004, 03:05 PM

The people that wanted to use the HDD power to drive the relay to completely disconnect the OPUS are going to have a problem. The OPUS will never turn on until that relay gets 12v across it, which will never happen unless that relay is closed.

Check the circuit diagram I posted :

The ignition will supply the power initially to the opus > PC will then turn on > then the relay will hold it until the PC is switched off

The only problem is the ignition trigger of the OPUS. Some unit dont like to be triggered as soon as power is applied. The safest way to do this is > apply power > wait a few seconds > then switch the ignition on to tirgger the OPUS.

The circuit diagram I have posted turn both the power and trigger at the same time. I dont know if OPUS like this...but that can be solved by adding a resistor and a capacitor as most likely the trigger mechanism of the OPUS doesnt require high current at 12v. All it should need is a 12V in milliamps so a resistor and a capacitor should be enough to delay the triggering of the OPUS on receiving the main 12V supply.

Hope thats clearer

**Ricky327** · 04-15-2004, 03:10 PM

Just in case anyone is looking to do this with an inverter, I wired up a relay on the HDD output accross the on/off switch of my inverter to do basically the same thing. I also put a relay accross it which was triggered by the ignition in the on position. My old MB automatically booted when power was supplied, so this worked well as an auto on feature.

Good post...Im sure alot of inverter ppl will follow the idea

**Riff** · 05-19-2004, 05:13 PM

Okay, I'm going to need to do the diode/relay mod. What kind of diode and relay will I need (links to radioshack models would be very helpful)? Would these work:

Diode

Relay

I'm a total electronics noob, so any noob advice appreciated! Thanks for your help.

**NoPistonPC** · 05-20-2004, 01:17 AM

Does anyone with an EPIA motherboard have this problem? I'm surprised this issue hasn't come up before. It seems like a significant one...

**gospeed.racer** · 05-20-2004, 01:28 AM

I have a epia M10000 and my solution for the usb hub staying powered up is this. And, keep in mind, mine is internal so accessing the usb wire was much easier than if it were external, but the same theory. All of my USB's appear to have constant power without this relay setup.

Cut the usb's red wire that runs to the motherboard, and connect it to the switched portion of the relay. Normally open contacts

Wire the relay coil to one of the molex connectors...5v or 12v depending on which relay you got. Mine was 5v.

When you turn on the pc, it fires up the buss and thus turns on the hub. Mine works great, never had a single problem. I have not had to install a cap or diode either. Your mileage may vary!

**NoPistonPC** · 05-20-2004, 04:14 PM

gospeed, that's too bad, i was hoping i wouldn't have to worry about this.

Do any of the standalone shutdown controllers have this problem? I will be using a regulator-bypassed ITPS in conjuction with an Arise 810H PSU. I posted my setup on this thread: http://www.mp3car.com/vbulletin/show...295#post206295

I know the ITPS pulses the reset button on the mobo on shutdown, but doesn't it also completely cut power to the 12V line going to the PSU (after the 45 second delay)? If so, I wouldn't have to worry about the USB current draw issue, correct?