What size inverter for 200w PC power supply? plus ATX shutdown question

**JiminyC** · 08-19-2005, 01:40 PM

Okay, if the answer is "200watts, silly" then I promise to stand in the corner for 15 minutes. But I'm going to ask because I don't think that's the answer because 200w refers to the amount of power it supplies, no?

Also, I'm thinking about hooking up my LCD to an ATX PS that's plugged into an inverter. Old AT power supplies used switches that are either on or off and would, therefore, power up my LCD as soon as the inverter supplied power. But ATX based computers use momentary switches.

So, does that mean that I will have to manually turn the PS back on every time the car is started and NOT have to manually turn it 'off' when I stop my car, because it will power down automatically?

Thanks

**emdzey01** · 08-19-2005, 02:00 PM

start your 15 minutes. lol

actually, you'd want something more than 200w. you'll never know when you'd need the extra power.

maybe 350w?

or just get an opus.

**JiminyC** · 08-19-2005, 02:28 PM

Originally Posted by emdzey01

start your 15 minutes. lol

PfffffT!

LOL

actually, you'd want something more than 200w. you'll never know when you'd need the extra power.

maybe 350w?

I just thought there might be some ballpark conversion from "DC power supplied by unit" to "AC power required by unit"

or just get an opus.

It's all money, convenience and ease of install right now. I've already got an inverter and even if it's not big enough, I can be ready to go within the next hour by running out and picking up a 400W inverter & an ATX power supply for $25-$30 each.

I've just browsed through some retail webpages and I can't find any info on power draw for PS units. The info's got to be out there......

Thanks

**JiminyC** · 08-19-2005, 02:53 PM

I guess this is a rough answer to my question.

[if] 300 is the maximum power of the PSU [and] 120 is your supply Voltage.

....The average PSU in a computer will operate at about 80% efficiency due to the nature of the circuits employed. This means that for the PSU to deliver 300W (va) as rated then it will actually draw about 375W (375va).

Whilst we know that your Computer will not run at full PSU load, if ever, we will use the full load to give the MAXIMUM cost that should be seen to any user.

So, a 200W PS could draw 250W if it was running at max and actually outputting 200W of DC. But my LCD draws much less than that, so I could probably get away with something even as small as a 75watt inverter assuming that there isn't some huge draw at the PowerSupply's startup.

**wizardPC** · 08-19-2005, 05:55 PM

BUY AN OPUS! OR AN M1-ATX

There's just no good reason not to.

**JiminyC** · 08-19-2005, 06:06 PM

Originally Posted by wizardPC

BUY AN OPUS! OR AN M1-ATX

There's just no good reason not to.

I appreciate your reply, but you're wrong. The good reason is called the money in my pocket. What you're suggesting will cost me four to eight times as much money that the PC power supply route will.

All I need to do is to power an LCD and I'd like something more stable at 12v than the cig-lighter plug that came with it.

So if it's a decision between spending $164.99 on a 150 watt Opus to power my LCD, or $19.95 on a 265 watt PC power supply, the answer is crystal clear. I'm buying the PC power supply.

**DarquePervert** · 08-21-2005, 10:23 PM

Originally Posted by JiminyC

I appreciate your reply, but you're wrong. The good reason is called the money in my pocket. What you're suggesting will cost me four to eight times as much money that the PC power supply route will.

Time is money, son. Remember that when you spend hours upon hours dicking around with your inverter, especially if you decide to go with a shutdown controller or add something to your setup.

All I need to do is to power an LCD and I'd like something more stable at 12v than the cig-lighter plug that came with it.

So cut off the cigarette lighter ent and wire it to a fused 12v line from the battery.

So if it's a decision between spending $164.99 on a 150 watt Opus to power my LCD, or $19.95 on a 265 watt PC power supply, the answer is crystal clear. I'm buying the PC power supply.

I wouldn't trust a $20 PC power supply as far as I can throw it. I know for a fact I can get some serious distance from one, especially if you use the connector cables and get some centrifugal force going....

**Nic** · 08-21-2005, 10:26 PM

Originally Posted by JiminyC

I guess this is a rough answer to my question.

So, a 200W PS could draw 250W if it was running at max and actually outputting 200W of DC. But my LCD draws much less than that, so I could probably get away with something even as small as a 75watt inverter assuming that there isn't some huge draw at the PowerSupply's startup.

i dont care if it says its a 200w power supply its not, power supplys are overrated unless of course you buy an expensive one

however the same goes with inverters, a cheap 200w invertor wont give you 200w of usable power

**JiminyC** · 08-23-2005, 12:43 AM

Originally Posted by DarquePervert

Time is money, son. Remember that when you spend hours upon hours dicking around with your inverter, especially if you decide to go with a shutdown controller or add something to your setup.

Thanks "dad"

Give me a break. I don't get paid for my weekend hobbies and I don't get paid for not spending my weekend on my hobbies. The fact is that I'll have more money in my pocket if I spend 6 hours on a $20 solution than if I spend 1 hour on a $200 solution.

And I didn't spend ANY hours "dicking around" with my inverter. I plugged it in and I was good to go. And in the near future I'll spend another couple bucks to hook up a silicon controlled relay and have my startup/shutdown needs taken care of as well.

So cut off the cigarette lighter ent and wire it to a fused 12v line from the battery.

Sounds like more "dicking around" than I'd like to spend my time on, but thanks for the suggestion.

I bought a $30 200-Watt atx power supply at microcenter and have it plugged into the 75 watt inverter I've owned for 6 years. I now have a very steady 12.1 volts of DC power running to my monitor and everything is working beautifully.