Cutting power to USB after computer has shutdown

**aoLhaTer** · 09-20-2004, 02:59 AM

ive already had a dead battery after i left my car for a day or two
thats why im so interested in all of this

thanks for your help
im gonna buy parts soon

**ptk** · 09-20-2004, 10:03 AM

just a suggestion
some might want to consider using DC-DC convertor by Universal Microelectronics to power your hub directly
http://www.umec-web.com

the UM2800 series comes with it's own remote power on/off circuitory.
you can hook up the power to the battery and the ACC to the remote power.

specs
Input Voltage Range,12V1 ..……….……………......… 9-18V
Isolation Voltage .……………….………..….... 500 VDC min.
Isolation Resistance .……………..………..... 108 Ohms min.
Case Grounding ......…………... Capacity Coupled to Input
Switching Frequency …………..……………..…….. 400KHz
Storage Temperature Range …………..... -55°C to +105°C
EMI/RFI ...........……………….. Six-Sided Continuous Shield
Dimensions ............……….........…....... 2.0×2.0×0.4 inches
(50.8x50.8x10.4mm)
Case Material ....……………...... Black Coated Copper With
Non-conductive Base

Control Voltage …………………..……………………………
On …..…………………………. >+2.5 VDC or Open Circuit
Off …………….………..…. < +0.8 VDC or Jumper to Pin 3
Converter Shutdown Idle Current ……………..……. 10 mA

**aoLhaTer** · 10-05-2004, 11:08 PM

i think im reading the schematic right but just want to make sure

is one of the diodes supposed to connect both contacts of the coil like this?

(possibly opening up a a can of worms here

)

**aoLhaTer** · 10-06-2004, 02:34 AM

hooked it up in the car and it works awesome

cut draw from 233mA to 7mA (which i think is just draw from the LED)

**rando** · 10-06-2004, 01:56 PM

Yes, that diode in your picture looks right. Congratulations on getting the solution put together and working! The 7mA draw you're seeing is just the Opus' internal consumption. That's consistent with my measurements.

**tejesh83** · 10-17-2004, 08:53 PM

I started having low battery issues again last week. Last time this happened, my battery died after repeated full discharges, so I replaced it with a Optima Yellow Top. Its held up for quite some time, but the problem reappeared recently. I was on vacation for a week, and I when I came back the battery was drained. Then last week, I didn't drive it for a few days because I got busy with classes, and the battery discharged again.

I came across this post while searching the forums. I applied the 5VSB mod yesterday. It appears to be working correctly. Hopefully, it solves my low battery problems.

Thanks for the schematics and other information!

**xtentialyst** · 10-20-2004, 01:50 PM

I have a slightly different hook-up. I wire nut the IGN, and Car Voltage in together, and use a switch to kill power to the PC. Though when the switch is on, the pc is always on, unless i turn it off in software or the hard switch. My question is, can't i get around the standby issue by taking one of the 12+ atx leads putting it across the coil so when its energized the switched 5vsb is closed, and once i lost 12+ like standby mode, that the 5vsb drops out?

That way i don't see any need for the diodes, and seems much easier too me. Any ideas?

**rando** · 10-20-2004, 02:39 PM

The M10k needs the +5VSB signal to be on in order to properly sequence the power supply. Without the SB voltage, the motherboard will pull PSON low and the power supply will come on as long as the BATT input is engergized. In the case where your IGN line is still low, this will cause the Opus/Computer to go into a never ending on/off/on/off cycle. In your case where your IGN and BATT Opus inputs are tied together, your solution might work (albeit somewhat by accident). For everyone else with an M10k, it wont.

Though I haven't tested it, the situation is probably the same for other mother boards.

More information is available in the the original thread on this subject (see the link in post #3 of this thread).

BTW, you still should put a diode across the relay coil to protect your Opus from kcik back.

**rando** · 10-20-2004, 02:47 PM

All of the above assumes you did a software only shutdown and didn't shut your Opus off with your switch. In that latter case, you don't have a 5vsb issue since the Opus is completely unpowered.

**EBJUSTIN** · 10-20-2004, 03:41 PM

Originally Posted by aoLhaTer

You are misinformed
The Opus WILL drain your battery
The 11v undervoltage protection only works if the computer is running; it will NOT work if the computer is powered off or in standby

The car will not start if it is battery is at 11V anyway...