Plug & Jack

[SavannahLion]

This is a little bizzare I guess. Probably why I can't figure out where to get the parts.

The biggest thing here is I want it to be bone stock. I don't want to have to pay $30 for just one part.

I was going to try using a C13/C14 combination (ie your bone standard PC power cord) but since I'm trying to feed multiple sources from this supply, a PC cord would be unsuitable. In theory, I think I can easily overload the 10amp limit of the PC cable trying to feed a PC, light, monitor, etc.

Then I thought I might just use a suitable extension cord and plug the female in into a male in from the cab. So I was going to go with a pigtail from the cab that I would plug into. But when I crushed the male end of the power cord moving one of my other cabs, I realized this was a dumb idea. A pigtailed power cord is just asking for it.  So then I thought having the male end of the standard NEMA 5-15 countersunk and installed as a wall plate, it would work well. Essentially a power "inlet" on the cab.

But for obvious safety reasons I don't think such fob would even exist. A cursory search seems to confirm this.

Well.. crap. What are my options now? I really want to be able to just use standard parts. An extension cord is about as standard as you're going to get. So is the C13 power cord. What else can I leverage for this? Any ideas?

[protokatie]

Not much help to you as I had a hard time following your post; but how in the HELL are you going to exceed 10 amps!!?? Computer ~ 1 amp, CRT ~ 1-2 amps, speakers ~ 1-2 amps, cold cathode tube ~1 amp. You aren't even half way to 10 amps. As far as I know, most entire circuit lines in a house are set at 15 amps each. Do you intend to have a vacuum cleaner as an input device for this thing???

[SavannahLion]

Basically, I want to use the standard plug you find on an ATX PSU and put it on the cab then use the standard power cord for that to plug in the cab and power the PC, LCD, etc. However.....

I was wondering about that myself, I think my math is way off.

I figured a hair under 1A on the PC so I tacked on 2A to pad. The LCD I calculated at 1/3A so I bumped it up to 1A. I actually forgot about the speakers. After my calculations and some number padding (for exactly the reason I forgot to consider the speakers), I came up with about 4A consumption at worst.

But when I start looking at specifications to get an idea of what I need to care for, my numbers get all out of whack. For example, looking at a selection of PSUs from Newegg, the lowest input rating I found was 6A with the highest at 10A for the "upper end" models. Even if I take a high end model and figure out how to actually use the full 900 watts it is supposed to have, I can't come anywhere near the 10A input value.

Looking at other cab examples here, it only further reaffirmed that I was missing some fundamental detail.

What am I missing here?  

Do I need to calculate waste energy lost in the conversion? If so, that's an insane amount of power being lost.

[protokatie]

Think Watts, not Amps. 10 Amps @ 12 volts is only 1 Amp @ 120 volts. Converting power usage to Watts will be easier to deal with. A 10 Amp rated power cord @ 120 volts is a 1200 watt power cord. You may be taking the amp values of things without considering the voltage.

[Ed_McCarron]

I was going to try using a C13/C14 combination (ie your bone standard PC power cord) but since I'm trying to feed multiple sources from this supply, a PC cord would be unsuitable. In theory, I think I can easily overload the 10amp limit of the PC cable trying to feed a PC, light, monitor, etc.

10A at what, 120v?  No clue where you are or what line voltage is - is 1200-ish watts.  Figure a few hundred for the PC, about the same for a monitor, and whatever the light is rated.  You hit 6-7A and it'd be impressive.

[SavannahLion]

I was going to try using a C13/C14 combination (ie your bone standard PC power cord) but since I'm trying to feed multiple sources from this supply, a PC cord would be unsuitable. In theory, I think I can easily overload the 10amp limit of the PC cable trying to feed a PC, light, monitor, etc.

10A at what, 120v?

Yes. Though those Home Depot and Rat Shack jack asses keep insisting my house is 100V. The pop shop agrees with my meter, but then they told me I couldn't build my Gorf adapter. So I can't win either way.

  No clue where you are or what line voltage is - is 1200-ish watts.  Figure a few hundred for the PC, about the same for a monitor, and whatever the light is rated.  You hit 6-7A and it'd be impressive.

Oh thank god, I was going ape ---steaming pile of meadow muffin--- crazy trying to figure why my numbers seemed all skewed. I was using Ohms law and using formulas like like this which came out with numbers both you and Protokatie are pointing out.

OK, so to prevent my brain from slipping again. Why does Random PSU have a total output of a mere 850W but show an input current of 12A? Is there something I'm not understanding about that? Is the power supply really only (counts off fingers) about 60% efficient? If I assume I find a way to load the PSU up to 850W (I know that's not possible, but for the sake of argument let's say I did) would I really blow off that much waste energy?

I'm actually embarrassed at this point.  I feel so 

[Ed_McCarron]

OK, so to prevent my brain from slipping again. Why does Random PSU have a total output of a mere 850W but show an input current of 12A? Is there something I'm not understanding about that? Is the power supply really only (counts off fingers) about 60% efficient? If I assume I find a way to load the PSU up to 850W (I know that's not possible, but for the sake of argument let's say I did) would I really blow off that much waste energy?

12A @ 120v = 1440W, if it were 100% efficient (in that perfect world we hear about in physics exams...)  But, yes, if it says that its a 850w power supply then 590W are being wasted at 100% load.  69% seems about right, mathwise.  Reality?  Probably not.

I suspect the 12A label is inrush current and nowhere near what it runs at.

[SavannahLion]

Jesus, I thought efficiency went up.

Oh well... thanks for the clarification. I'm reverting back to my original two ideas for powering the cab.

Now I have to figure out where to put the speakers I forgot to incorporate.  Maybe I can just punch a hole in the front and add a chrome jobbie.

Darn it.

[Ed_McCarron]

Jesus, I thought efficiency went up.

Not if you want price to keep going down.

[SavannahLion]

Jesus, I thought efficiency went up.

Not if you want price to keep going down.

Interesting trend. Environmentalists are a funny bunch. 

[pmowry]

Thanks for the thread  I bought a Schurter DD11 Series plug to put on the back of my cabinet before I thought about the current drawn.  It 's rated for 7 amps. So from this thread it sound like I'll be ok.  I'll solder a powerstrip to it this weekend and see what happens.

[MonMotha]

FWIW, most PC supplies are ~75-85% efficient at mid-load and ~60-75% efficient at full load.  It's pretty pathetic.  There's an "80+" initiative that you can look for the logo on the box of a supply.  That, in theory, means that the supply is at least 80% efficient at near full load.  Some of these can top 90% at mid-load.  Remember that if you don't have it fully loaded, it won't draw the nameplate current.  It'll just draw what it needs to power the PC plus any losses in the PSU.

The nameplate logo usually does NOT include any inrush, believe it or not.  Inrush on most cheap PC supplies can be on the order of 50-100A (no kidding!).  It's just short enough to not trip your breaker.

I generally would not recommend actually running a PC supply at more than 80% of its stated capacity.  They're usually just not actually designed for it.  Most cheapies aren't even capable of much more than 60% of stated output capacity for more than a few minutes.  Some REALLY cheap supplies are even rated in INPUT, not output, meaning that the "850W" rating means that you can (maybe) safely pull 850W from the wall, not deliver it to the load.  Fortunately, most PCs don't actually need more than ~250-300W of DC power.  People have been conditioned to buy really big PC supplies due to this overrating activity that goes on.

As for wall voltage, it does vary.  Most places I've checked in the USA run between 115-120V circuit unloaded, which is generally accepted as the norm in the USA.  I have a friend who's house runs a little high at ~123V, and some older dwellings are at more like 110V.  USA wall voltage is "supposed" to be 120V but can be as high as 125V.  100V is considered very low in the USA, but Japan still runs 100V for some reason.  If your wall voltage is 100V, you should have the power company turn it up some; they can do that.  Europe has standardized on 230, IIRC.  The rest of the world just picks something - usually 220-240V or 110-120V, and it's usually a "nice" number, but there is of course local variability which includes not just what the power company actually delivers but how loaded the circuit is.

[Ed_McCarron]

Inrush on most cheap PC supplies can be on the order of 50-100A (no kidding!).  It's just short enough to not trip your breaker.

Wow. No ---steaming pile of meadow muffin---.

[protokatie]

Inrush on most cheap PC supplies can be on the order of 50-100A (no kidding!).  It's just short enough to not trip your breaker.

Wow. No ---steaming pile of meadow muffin---.

I knew it was bad, but never figured it could be that bad, so I had a looksee on wikipedia and found this:

When a transformer is first energized a transient current up to 10 to 50 times larger than the rated transformer current can flow for several cycles. This happens when the primary winding is connected around the zero-crossing of the primary voltage. For large transformers, inrush current can last for several seconds. Toroid transformers can have up to 80 times larger inrush, because the remnant magnetism is nearly as high as the saturation magnetism at the "knee" of the hysteresis loop. This is caused because the transformer will always have some residual flux density and when the transformer is re-energized the incoming flux will add to the already existing flux which will cause the transformer to move into saturation. Then only the resistance of the primary side windings and the power line are limiting the current.

TEN to FIFTY TIMES!!! 

[MonMotha]

Actually, PC power supplies don't have 60Hz transformers in them.  Most of the inrush goes to charging up the bulk ripple filter caps on the output of the bridge rectifier.  An NTC component is often used to limit this, but cheap designs won't have that (I'm not seeing one on a 430W Antec I've got disassembled next to me), and they only limit the inrush so much.

So yeah, no ---steaming pile of meadow muffin---   The transient is pretty quick though (on the order of a few dozen msec).  You'd probably even have trouble catching it with an analog multimeter.  The quickness is why it won't trip your breaker, but why your lights dim a little bit (if you watch carefully) when you first plug in your PC supply.