Cutting power to USB after computer has shutdown

**aoLhaTer** · 09-13-2004, 12:51 AM

im trying to find tutorials on how to read schematics but google hasnt found anything beneficial
if i was an ee id understand this but im not

could you just try to explain it to me so i can understand what to do

**rando** · 09-13-2004, 01:25 AM

I already described it in plain english (before I posted the schematic) in the other thread (see pg1 of this thread for link to the other thread). People didn't understand the English so I posted the schematic. Do you know anyone who can read schematics? Mabye a car audio shop? Here is a basic set of steps you should follow.

0) Disconnect power from your computer and peripherals.
1) Buy an ATX power extension. Search google to find the pin outs. Locate and cut the PSON and +5VSB wires.
2) Hook the two sides of the +5VSB wire (the one you cut in step #1) to one set of your relays switch contacts. Do the same thing for the PSON wires -- on the other set of relay switch contacts.
3) Hook your IGN wire to a diode anode. Hook one a +12V PSU output to another diode's anode. Hook the cathodes of all three diodes together and to one side of your relay coil.
4) Hook the anode of your third diode to the other side of the relay coil and to ground.
5) Sandwich the ATX extension (with relay mod you just built) between your PSU and CPU.
6) Call a friend that can read schematics and ask them to verify your work. Double check it with a meter.
7) Reconnect the power and have fun.

Note: You can tap the +12V and GRND wires directly from the ATX extension also. This should help to keep your wiring clean. If you do it right, the only extra wire going into your ATX extension should be the IGN wire. Everything else can be zip tied and/or taped up nicesly. Throw on some loom if you want it to look really nice.

**aoLhaTer** · 09-19-2004, 01:54 AM

one more question
did you use a perfboard to assemble this or just wire stuff straight off the cables?

**trioptimum** · 09-19-2004, 03:22 AM

The Opus 150 will NOt let the computer drain your battery, it will cut off power whenthe voltage drops too low, so that the car will still start. There is no reason to wrry even if the computer doens't turn off at all, it will cut off power completely before the battery gets to low to allow your car to start again. At least they claim so :P. I've never left it running ot find out - if it doesn't shut odwn for me, I unplug it. It goes into hibernat,e not standby, so it should have no power after shutdown.

As for USB staying on, depending on your car battery and the devices you have hooked up, it shouldn't be a problem (mice and stuff are ok, USB lights and fans and vacuums and fish tanks - avoid high power stuff ^^). If yours dies often, try to find a fix, or just invest in a better battery. Another idea is to hook up a USB hub (either try to find a DC usb hub if one exists or plug one in to an inverter) and plug the stuff in to there. Worst comes to worst, run a seperate line for the USB power and put a switch on it.

Myself, I have a redcell deep cycle battery, and I haven't lost charge once since I got it 6 months ago, including leaving my bright lights on for 3 days in a row. It is safe to de-charge completely and re-charge, whereas doing that to a normal battery is harmful to it.

One problem I have wiht my Opus that I don't like is if the PC freezes for some reason it will NOT cut power when the PC doens't respond to the power switch being shorted. I wish it would try shorting the power switch for 4 seconds (Hard-off) followed by cutting the power after a minute or so if it dind't work, or to have a jumper for this setting anyway would be nice. I occassionally have to go unplug it if it gets stuck.

**aoLhaTer** · 09-19-2004, 03:31 AM

Originally Posted by trioptimum

The Opus 150 will NOt let the computer drain your battery, it will cut off power whenthe voltage drops too low, so that the car will still start.

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

**lookinco** · 09-19-2004, 04:18 AM

I have disconnected the 5v going to the USB port on my shuttle. Then I just use a usb hub with external power supply powered by a inverter (inverter also power other stuff like PS2 and VCR). This way power to USB is cut when car is off.

**aoLhaTer** · 09-19-2004, 07:06 PM

i metered my carputer with it off and got a reading of 214mA
is that high or low?

**rando** · 09-20-2004, 02:53 AM

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

So let's be precise here. The low battery protection only forces your computer off when your battery voltage dips too low. The 'off' state in this case is no different that the normal Opus off state. In other words, it will still leave the +5VSB rail on.

Let me repeat (and this has been said in probably 1000 other threads), the +5VSB rail on the 150W Opus is ALWAYS ON as long as it's hooked to the battery.

**rando** · 09-20-2004, 02:54 AM

Originally Posted by aoLhaTer

one more question
did you use a perfboard to assemble this or just wire stuff straight off the cables?

Just strait to the cables but you can use a perf board if you want.

**rando** · 09-20-2004, 02:57 AM

Originally Posted by aoLhaTer

i metered my carputer with it off and got a reading of 214mA
is that high or low?

Yes, I believe that is high and will negatively impact your battery life; it will probably also leave you with a dead battery sooner or later. The best way to tell is to compare that measurement against what your car pulls (when off) with the computer disconected.