Question on powering USB devices off of 5v line on molex connector

S4Per · 11-02-2006, 10:32 PM

Hey Folks,
So I got the answer back from Aopen that there's no way I can have the USB bus powered off during standby. This forces me to the old way of cutting open the USB cable, cutting the +5v and ground lines on the USB cable, and splicing these into the respective lines on the molex connectors on the mobo so the USB device receives power only when the PC is on. Questions on this:

1. Can I connect 3 seperate USB cords to the same spot of a single molex connector? i.e. I have 3 USB cords that I need to do this with (some devices are not happy being on a hub, otherwise it'd be one cord) and I'm wondering if I need to pick 3 seperate molex connectors or sections on molex connectors to power these correctly? Can all 3 be spliced into one spot on the molex lines?

2. If I can do all into one spot, I'd like to do this via some type of connector, do such things exist? Example: the molex cables terminate on a connector that has inputs for 3 other connectors...something like a 3-to-1 AC power outlet.

4. Is there a better way to do all of this?

TIA,
Per

Emo · 11-02-2006, 11:07 PM

my question is.. why do you want to shut off the power at all?

I have all of my devices plugged in and they dont shut off when the car/pc are off but that doesnt bother anything does it?

Wiredwrx · 11-02-2006, 11:13 PM

Quote: Originally Posted by Emo

my question is.. why do you want to shut off the power at all?

I have all of my devices plugged in and they dont shut off when the car/pc are off but that doesnt bother anything does it?

Ya, it draws power, which will drain his battery.

Michael

S4Per · 11-02-2006, 11:14 PM

right. battery drain.

Wiredwrx · 11-02-2006, 11:14 PM

Quote: Originally Posted by S4Per

Hey Folks,
So I got the answer back from Aopen that there's no way I can have the USB bus powered off during standby. This forces me to the old way of cutting open the USB cable, cutting the +5v and ground lines on the USB cable, and splicing these into the respective lines on the molex connectors on the mobo so the USB device receives power only when the PC is on. Questions on this:

1. Can I connect 3 seperate USB cords to the same spot of a single molex connector? i.e. I have 3 USB cords that I need to do this with (some devices are not happy being on a hub, otherwise it'd be one cord) and I'm wondering if I need to pick 3 seperate molex connectors or sections on molex connectors to power these correctly? Can all 3 be spliced into one spot on the molex lines?

2. If I can do all into one spot, I'd like to do this via some type of connector, do such things exist? Example: the molex cables terminate on a connector that has inputs for 3 other connectors...something like a 3-to-1 AC power outlet.

4. Is there a better way to do all of this?

TIA,
Per

What is a "molex connector on the mobo" What are you refering to?

Michael

S4Per · 11-02-2006, 11:21 PM

molex connector = the connector that supplies power to your standard IDE hard drives. These are a great source for tapping power if you want something only on when the PC is on. The 4 wires supply +12v, +5v, and two grounds (yellow, red, black, black). These only receive power when the PC is turned on. So - you connect the power and ground cables from your USB cable that leads back to your device/hub (it has 4 wires, the other 2 are for data) and splice these into the red and black wires on the molex connector.

perhaps wording was poor..i mean to say tapping the wires that lead to the molex connector (although getting a male/female pairing on the connector itself is also possible).

good info at: http://www.playtool.com/pages/psucon...tml#peripheral

Wiredwrx · 11-02-2006, 11:25 PM

Quote: Originally Posted by S4Per

molex connector = the connector that supplies power to your standard IDE hard drives. These are a great source for tapping power if you want something only on when the PC is on. The 4 wires supply +12v, +5v, and two grounds (yellow, red, black, black). These only receive power when the PC is turned on. So - you connect the power and ground cables from your USB cable that leads back to your device/hub (it has 4 wires, the other 2 are for data) and splice these into the red and black wires on the molex connector.

perhaps wording was poor..i mean to say tapping the wires that lead to the molex connector (although getting a male/female pairing on the connector itself is also possible).

good info at: http://www.playtool.com/pages/psucon...tml#peripheral

Dude, I know what Molex connectors are. They come from the PS, NOT FROM THE MB. That was the confusing part. (Don't take this the wrong way)

Yes, you can tap into a single molex to power your USB devices. USB is specd at 500ma per device. 3 devices will use 1.5 amps. That connector is easily capable of that. The wires should be at least 18 gauge, and preferable 16 gauge, if you are gonna run 5 or 6 feet or less.

Michael

P.S. That link is great, I will try and get them to add it to a FAQ or something.

S4Per · 11-02-2006, 11:29 PM

i figured it was my wording..typing in a hurry, sorry ;-)

what if i have 2 devices and one hub? the hub has 4 devices on it: touchscreen, OBD-II cable, RF keyboard, and DVD player. The DVD player and the hub have external power being supplied by the second output of the Carnetix 1900....think I'm still good to go?

Wiredwrx · 11-02-2006, 11:31 PM

Quote: Originally Posted by S4Per

i figured it was my wording..typing in a hurry, sorry ;-)

what if i have 2 devices and one hub? the hub has 4 devices on it: touchscreen, OBD-II cable, RF keyboard, and DVD player. The DVD player and the hub have external power being supplied by the second output of the Carnetix 1900....think I'm still good to go?

I am not very familiar with the carnetix, but maybe you can power all the USB stuff off the carnetix.

In any event, the connector is good for, I think I read, 14 amps. You should be fine, as long as your cable is sufficient to handle the amperage. I would not go smaller gauge then 16, perhaps 14 to be ont he safe side, and don't run it too long. EDIT: I MEAND LENGTH WISE, not time wise.

Michael

S4Per · 11-02-2006, 11:34 PM

cool. thanks Michael :-)

Wiredwrx · 11-02-2006, 11:36 PM

Quote: Originally Posted by S4Per

cool. thanks Michael :-)

My pleasue.

Michael

PSYKO_Inc · 11-03-2006, 01:50 AM

Not trying to totally derail the thread here, but would it cause any problems with the OS, etc., to shut down power to the USB accessories while the pc is still powered on? I was throwing around the idea of building a simple 5v voltage regulator (possibly using something like these: http://cgi.ebay.com/5-National-LM267...em190028231041 ) to power a 7-port USB hub and a USB DVD drive in my dash. I could power this regulator with a relay triggered by the ACC line from my ignition switch, so the USB items would power down when I turn the key off, and my shutdown controller would put the PC into standby from the same trigger. Would this be feasable, or is there something else that I'm not taking into account here?

Wiredwrx · 11-03-2006, 10:43 AM

Quote: Originally Posted by PSYKO_Inc

Not trying to totally derail the thread here, but would it cause any problems with the OS, etc., to shut down power to the USB accessories while the pc is still powered on? I was throwing around the idea of building a simple 5v voltage regulator (possibly using something like these: http://cgi.ebay.com/5-National-LM267...em190028231041 ) to power a 7-port USB hub and a USB DVD drive in my dash. I could power this regulator with a relay triggered by the ACC line from my ignition switch, so the USB items would power down when I turn the key off, and my shutdown controller would put the PC into standby from the same trigger. Would this be feasable, or is there something else that I'm not taking into account here?

The link you provided would probably work, but there may be easier devices to use, the easiest among them being your DC-DC PS. It is fully regulated, and if you are not exceeded the specs, that would be the easiest.

There are also Point of Load devices on the MP3car store.

Also, while perhaps "old school", I like the LM338K regulator. It is adjustable, and will supply up to 5 amps I think (3 or 5, I forget), and needs just 2 external components. I am not sure how many parts the link you proveded requires. Also, the link looks prett SMD like, so it might be hard to work with.

As for powering the USB devices with the computer off, there should be no problem. In the long run, it MIGHT cause the device to "wear" quicker, but I doubt you will notice.

Michael

Emo · 11-03-2006, 01:47 PM

Quote: Originally Posted by Wiredwrx

Ya, it draws power, which will drain his battery.

Michael

yeah I figured that much but just wanted to make sure..

the thing is... how long does this have to go on until you actually drain your battery? I mean I drive my car every day and the most it stays in my driveway is less than 8-10 hours a day the most

-Emo

S4Per · 11-03-2006, 02:44 PM

Emo - mileage will vary. For me, the battery gets low / potentially won't start if I don't run it for 2 days. That's WITHOUT any USB devices still being on while in standby, i.e. only the mobo is being powered for its standby state.