P2140 Setup Question

**mdd5148** · 03-11-2008, 03:37 PM

*Edit: It looks like there are wires going to no where unless you view the full-sized thing.

so here is the diagram of my installation.

I know that it isn't the best diagram but it should work... I got a multi-meter the other day and I am going to test everything tonight. In the diagram you should see that there are some things that connect to the car's head unit labeled "wiring harness". I know this is a horrible description but to be honest it is a proprietary plug that goes into the back of the head unit. I assume for the screen that there is a power lead and a ground as well as a few other things but I am not sure. Same for the Car2Pc plug.

**Bugbyte** · 03-11-2008, 04:11 PM

What powers the Car2PC adaptor?

All I can say is that I would suspect the USB cable from the hub to the Mac. I'd get the Mac working first before hooking ANYTHING up to it besides the VGA out. That includes audio.

**mdd5148** · 03-11-2008, 04:51 PM

I just went and checked the current of the usb devices that are sitting in the car right now. The screen and the Car2Pc adapter (I guess I left out the bluetooth dongle that I have too in my diagram.) Right now the car does not have the carnetix or the computer I was just checking the current on the devices to see what I am plugging my computer into as bugbyte suggested.

So I took one lead on my multi-meter and grounded it with the cigarette lighter and the other end and tested the hot end of the usb leads. I got nothing on the screen. But then to my suprise I got 14v on the Car2PC usb (wowza) think I found the guilty party....

**mdd5148** · 03-11-2008, 04:55 PM

Originally Posted by Bugbyte

What powers the Car2PC adaptor?

The car2pc adatper plugs into the back of the head unit and works fine without the usb part as a simple aux. line in. I guess the head unit must power the unit? This is an area where I do have limited knowledge.

**Bugbyte** · 03-11-2008, 05:58 PM

Originally Posted by mdd5148

So I took one lead on my multi-meter and grounded it with the cigarette lighter and the other end and tested the hot end of the usb leads. I got nothing on the screen. But then to my suprise I got 14v on the Car2PC usb (wowza) think I found the guilty party....

Ouch. That would do it, methinks.

**mdd5148** · 03-13-2008, 08:12 AM

Ok so I think that I had my points wrong when I was using the multimeter and therefor was reading the wrong voltage (I didn't feel right about a USB cord carrying 14v). So I rechecked it and found that the Car2PC is really carrying .005v I think (It was on the 2v selector and screen read .005) This is still the only device that has current on its own but would that be enought to zap the computer... I mean I guess it would as it is going in the wrong direction.

Also I hooked my laptop up to the screen usb and got a USB error code 10. I think if I find the right drivers for this thing then I will be in business.

**NeonDev** · 03-13-2008, 10:14 AM

i thought usb would work on + or - 5 volts... so i don't think that is your problem is the direction of the current. Im not an electrician tho. have you googled a USB error 10?

Edit: i googled that error and it seems to point to INSUFFICIENT power

**Bugbyte** · 03-13-2008, 10:30 AM

Originally Posted by mdd5148

Ok so I think that I had my points wrong when I was using the multimeter and therefor was reading the wrong voltage (I didn't feel right about a USB cord carrying 14v). So I rechecked it and found that the Car2PC is really carrying .005v I think (It was on the 2v selector and screen read .005) This is still the only device that has current on its own but would that be enought to zap the computer... I mean I guess it would as it is going in the wrong direction.

Current is different from voltage. .005 volts is practically zero and wouldn't be able to 'push' enough current to hurt the Mini.

Voltage is like water pressure. The higher it is, the more electrical 'pressure' there is.
Current is like the volume of water delivered.
Resistance is like the size of the hose. Lowering resistance (making the hose bigger) allows more current to be delivered.

So .005 volts is very, very little pressure, which means any current that is being delivered is very little. Not enough to short something out.

When you measure voltage, make sure you use the next highest setting on the meter. If you expect to measure 5 volts, set the meter to higher than 5, say 12 or therebouts.

**mdd5148** · 03-13-2008, 12:15 PM

Originally Posted by Bugbyte

When you measure voltage, make sure you use the next highest setting on the meter. If you expect to measure 5 volts, set the meter to higher than 5, say 12 or therebouts.

Ok, good advice... I probably need to do round 3 of testing. The 2v setting is deff. the wrong setting for this testing situation.

**mdd5148** · 03-16-2008, 10:26 AM

I now have the touch screen working! I really want to thank everyone for their help. I did some more testing with my multi-meter and I think that the reason that my computer is not turning on and off from the carnetix is due to a bad y-cable. One of the ends was broken in the box when I got it and I tried to solder it back on but the multi-meter meter confirmed that this was not a good connection. This must be the problem, I will try to get a new one.

On a side note, my screen has some scan lines and color issues so I think that I will be taking apart my dash this today to see if I can swap out the vga cable to solve that.