ATX PC startup problem

SuperMatty · 10-14-2001, 09:31 PM

I have an ATX PC hooked up to a relay and a 140W inverter in my car. When I turn the key on the ignition, the radio comes on. I then go to press the momentary button to power up my computer, but it will not start. Upon looking at the inverter, I see that the light on it is flashing instead of being constant. Now, if I cycle the on/off switch on the computer's power supply, the inverter light suddenly becomes constant now, and I power the machine up again using the momentary button. So my question is, what is the problem here and what is the easiest way to solve it. I had previously used this inverter with an AT style computer (but not with a relay) and it worked perfectly starting the machine up.

SuperMatty · 10-14-2001, 09:32 PM

Just to clarify, after I cycle the power switch on the PC's power supply, and again attempt to power up the machine using the momentary switch, the PC *successfully* boots up.

Aaron Cake · 10-15-2001, 08:51 AM

It sounds like the ATX supply is trying to start the computer as soon as it receives power. Is there an option in the BIOS to disable automatic startup (or power failure recovery)? The inverter may be going into fault mode because of this.

SuperMatty · 10-15-2001, 09:32 AM

There is no option like that in the BIOS, and I need to use the momentary switch to start it each time.

Aaron Cake · 10-16-2001, 08:46 AM

Hmm....Have you tried plugging it into a regular outlet? Does it behave the same way?

SuperMatty · 10-16-2001, 09:33 AM

In a regular outlet it works perfect. I am going to be replacing it with a different power supply today to see if it makes a difference. I found out last night that this problem is somewhat intermittent. Occasionally when I go out, start the car, and try to turn the computer on it will actually come on, but about 3 out of 5 times it won't.

SuperMatty · 10-21-2001, 06:19 PM

Well after replacing with a different (switchless) power supply, still when I start the car, the inverter goes into a fault mode and the light on it just flashes until I unplug, and re-plug in the computer at which point the inverter light remains constant and I am able to start the computer up. Any suggestions? Anyone?

jboy · 10-21-2001, 07:59 PM

I see 2 possible problems

1)The inverter sounds small
140w may be enough to maitain the computer, but during startup the computer ps may draw much more power , at the same time the car is drawing much more power and may be droping the supply voltage below the inverters limit causing the inverter fault.

2)if the inverter remote input is hooked up to the acc from the ignition this would cause the inverter to turn on in the acc position then off when you crank the engine then on again when the key returns to acc because of how the switch is wired. this short on off on cycle may be the cause,
try just turning to the acc position w/o cranking the engine, if this works and you want the key to there is another circuit in the ing switch that stays on in all but the off position, possibly the coil or fuel pump power.

SuperMatty · 10-21-2001, 08:21 PM

Well, the inverter is is capable of putting out 400W for short amounts of time according to the specs. I tried just turning the key to accessory, still the same problem, even without cranking the engine. The inverter just flashes on and off until I unplug the PC, and then if i wait a few secs and then plug the PC back in and try to fire it up it will work.

SuperMatty · 10-21-2001, 08:41 PM

Just another thing, could it be that the relay isn't large enough? I believe it only supports up to 10A.

jboy · 10-22-2001, 09:11 AM

What is the PS rated for,
even a small 120w ps can draw over 400w for a very short surge at startup

SuperMatty · 10-22-2001, 02:47 PM

250W power supply in the computer.

jboy · 10-22-2001, 04:04 PM

The inverter is way too small!
the 250w ps may only draw about 100w cont. to meet the power needs of your system but inrush current can be 2-5x the ps max rating until the internal caps are charged

Solution 1
Get a bigger inverter, 300-400w cont.to be safe

Solution 2
find the total power your system needs,
and get a smaller PS that meets the systems power needs + say 10-20% more for stable operation and an inverter that can provide
20-30% more than that cont. due to the computer ps inefficiency w/ a surge rating that can handle the startup

Solution 3
Get a DC-DC ps/2 power supply, they seem expensive but a powerfull enough inverter can cost nearly as much and the inverter and pc ps are both wasting alot more power than a dc-dc converter alone.

SuperMatty · 10-23-2001, 12:45 PM

Where is a good place to purchase a Dc-DC ATX power supply?

jboy · 10-23-2001, 08:31 PM

Keypower has afew to chose from depending on case (at/atx) check this site
http://www.keypower.com/dcdcnew.html