dc-dc power supply wont work while car is on

**xen** · 02-11-2006, 01:25 PM

ok i have a dc-dc 100watt supply powering just a hard drive under my drivers seat. it works fine when the car is off or in acc. but when i turn the car on it no longer powers the hdd.

the +power is running straight from the battery(tried alt too) and the ground is hooked to a seat bolt(i tried it with ground hooked straight to battery too)

any suggestions/solutions to this will be appreciated

edit: also so you know, its not dying at crank

**DarquePervert** · 02-11-2006, 04:00 PM

You need to provide some specific information about what you have.
I don't know of any 100w DC-DC PSU on teh market. There's a 90w and 120w Opus Solutions unit.
We also don't know what the specs of the HDD or PC are, either.

It sounds liek you don't believe the PSU itself isn't providing output power. Get a digital multimeter and check the output power. It could be as simple as a blown fuse somewhere or as sucky as a dead PSU.

**xen** · 02-11-2006, 09:07 PM

Originally Posted by DarquePervert

It could be as simple as a blown fuse somewhere or as sucky as a dead PSU.

its not dead. like i said it works fine when the car isnt running

here is a link to the psu
http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MEWN:IT

the hard drive is a 10 gig seagate taken out of an xbox

**meddler** · 02-11-2006, 09:18 PM

I would make sure that your power supplying the PSU is still providing 12V when the engine is running. It might be at 12V when the key is in ACC buy not in the ON position.

EDIT: I just had a look and this PSU only has a +ve and -ve input. +ve is white and -ve is black.

**DarquePervert** · 02-12-2006, 06:14 AM

Also, that PSU doesn't regulate the 12v line. I know for a fact that XBox HDDs are 3.5" drives, which means they require 12v power. So you're basically sending fluctuating voltage from the car's electrical system. That can go as low as 8v, even when the car is running.

I do believe you need a regulator, my friend.

**xen** · 02-12-2006, 07:26 AM

do you normally need a regulator for a dc-dc psu? or did i just get a crappy one?

ok just tested the voltage and off its at 12.2 and running its 14.2

what would be a simple solution?

**DarquePervert** · 02-12-2006, 07:55 AM

Originally Posted by xen

do you normally need a regulator for a dc-dc psu? or did i just get a crappy one?

ok just tested the voltage and off its at 12.2 and running its 14.2

would would be a simple solution?

You just got a crappy one.
Actually, in general, these units aren't crappy, but they aren't designed specificatlly for vehicle use. They're designed to work off a onstant 12v power source, not a fluctuating one like your car.

Simple solution? Get a 12v regulator.

If you gave us some more information about the entire system, rather than just the HDD that you're trying to power, we might be able to provide some alternatives.

**xen** · 02-12-2006, 09:45 AM

Darqueperv i'm only trying to power a hdd. the front of my car stereo has a usb port. i origionally had an inverter and external case powering the hdd, but wanted to eliminate all that crap

ok so i have it working now but its kinda scary. i used the power from my glove box light (which never f'n turns of anyways) and no ground. actually it grounds when i plug the usb cord into the front of the stereo. the psu and hdd shutdown when i pull the usb out

everything seems to be working fine and there is no interference in the sound. but i'm kinda concerned about using the usb for ground. just doesnt seem right. actually i have no idea why it even does that considering that thats on the other end of the psu. but whatever works i suppose. i'll keep my fingers crossed that my car doesnt burn down(goes to check)

wallow in my newbishness