Has anyone tested a CarNetix CNX-P1260 using a 12V PSU?

**Vacheron** · 01-14-2005, 03:19 PM

I am currently in the process of assembling my new car PC indoors before installing it in the car and am attempting to get the CarNetix CNX-P1260 to work correctly from a 12V, 3Amp power supply I am using to simulate the car battery (with a switched feed from the PSU to simulate the ACC line).

With no load connected to the CNX-P1260's 12V output, both the LED indicators on the 1260 PCB behave exactly as the manual says they should and the measured output is a regulated 12V. However, the instant a load is connected to the 1260s output, the bench PSU's overcurrent protection kicks in and throttles back the power. The 1260's will then remain in this "high current drawing" state even when the load is removed. The only way to return it to normal is to cycle the input voltage to the 1260.

As every other element of the 1260's operation appears to be functioning (it is even controlling the ACPI, it just cant supply the power!), I am wondering if anyone else has attempted to test their 1260 in a similar way?

I have considered that perhaps the 1260 initially pulls a short high current burst that is tripping up the sensitive overcurrent protection in a PSU, but would prefer not to risk further damage by connecting the unit to the relatively unprotected, high current capacity of a car battery if there was a fault with the unit?

All comments appreciated!
Vacheron.

**RJP350Z** · 01-14-2005, 04:00 PM

I have my P1260 and my Xenarc MP-SC1 setup on my workbench right now. The only issue I had was I couldn't use the 12V Brick Power supply that came with the Xenarc because of basically the same issues you're having. I'm using a regular ATX power supply from an old desktop I had laying around and everything works perfectly.

**Vacheron** · 01-14-2005, 04:38 PM

Thanks RJP350Z.

I tried using the 5A brick power supply that came with my Travla C134 case as a supply too and got the same overcurrent fallback symptoms.

When run through the 1260 the 5A travla supply wouldn't even start my LCD and it's brick is only rated at 1.25A max!

It therefore definately sounds like there may be some large startup spikes from the regulators in the 1260. I will try an ATX supply tomorrow as you suggested and post back. (At least ATX PSUs are one component I have no shortage of!)

**MikeH** · 01-14-2005, 07:16 PM

You guys are correct. Most of the power "bricks" that come with the various peripherals (cases, screens) have a very sensitive overcurrent protection circuit that trips when the P1260 starts up. I have not yet seen anyone successfully use one of these bricks to power the P1260. HERE is an example of one that came with my Travla case & Morex PSU that does NOT work. However, the "spare ATX PSU" technique seems to work well.

**Vacheron** · 01-15-2005, 10:30 AM

Thanks for confirming that MikeH. Would you believe that I did check the Carnetix forums before posting, but only looked in the V1.5 forum.

I tried the ATX psu solution and it did manage to start up the PC but at it would only provide a 9V throttled output to the 1260 (more overcurrent protection no doubt, maybe the PSU was too clever for it's own good!)

. This resulted in a noisy output from the 1260 and massive amount of coupled audio noise from the onboard sound. The 1260 was having trouble coping with the input as well which could be seen by flickering and pulsing of the 1260s status LEDs.

This called for solution 3, Haul lead acid battery out of car and into house!

Still concerned that the 1260 may be damaged from my earlier encounters I test drove the output into half a dozen PC fans. No problem.

Happy now to connect the Travla, I did so and everything worked perfectly.

All I need to do now is replace the transorb on the VIn to the 1260 as it went up in smoke and failed s/c during the initial bench PSU tests (probably the high speed repetition and di/dt of the voltage fallback from the bench PSU).

..... oh well, that's what I get for being cautious! (If i had just stuffed it in the car I would probably have been one transorb better off and an extra day further forward!)

Thanks again for everyone's help.

http://www.vacheron.btinternet.co.uk/Dscf1687.jpg

**RJP350Z** · 01-15-2005, 01:40 PM

Glad to see you got everything working. As for the ATX PSU usage... I had to connect the ATX power supply to an old motherboard laying around and connected the P1260 to one of the hard drive power connectors. I did this because most newer ATX power supplies need to have a load on the 5V bus in order to power on and regulate correctly. You can't just short the PS-On (Pin 14.. I think) to ground like you could with older ones.

**Vacheron** · 01-15-2005, 02:02 PM

Originally Posted by RJP350Z

You can't just short the PS-On (Pin 14.. I think) to ground like you could with older ones.

Ah, That probably explains the regulation and why the old "short the black to green wire trick" didn't work properly then!
The PSU would power down whenever the link was removed.

Me being me though, I just jammed the wire in permanently and carried on!

**Arathranar** · 01-15-2005, 06:32 PM

Originally Posted by RJP350Z

Glad to see you got everything working. As for the ATX PSU usage... I had to connect the ATX power supply to an old motherboard laying around and connected the P1260 to one of the hard drive power connectors. I did this because most newer ATX power supplies need to have a load on the 5V bus in order to power on and regulate correctly. You can't just short the PS-On (Pin 14.. I think) to ground like you could with older ones.

I'm doing it with a pretty new SeaSonic psu (it's totally silent - I have to put my hand behind it to check the fan is running

) and it's working just fine. So not all new psu's don't allow this. It's suppling 7A @11.68V to my PW-200V just fine for indoor testing.