Another Pico PSU question

taidi · Post by **taidi** » Thu Oct 08, 2009 5:39 am

I'd like to move my system into a wood (MDF) box and use a Pico Power Supply but have a couple of uncertainties about doing this.

Would a Pico 150 Watt PSU be sufficent to power the system as it is...?

Main Board = Asrock ALiveNF6G-DVI
CPU = Athlon 64 3800+ Lima Core
RAM = 2 x 1GB Crucial 1.8V
HDD = Seagate ST3160811S
DVD = Lite-On LH20A1S

I could if needed swap the HDD out for a drive with a lower power consumption - a 2.5" drive or a Samsung HD502HI and even use an external DVD writer.

My other concern is the earthing arrangement of the Pico PSUs. As I understand it there is only a 2 wire connection between the power brick and the PSU. Does this present any problem with earthing the system ?...I have to admit I don't know if a PC needs to be 'grounded' or not.

barefootzero · Post by **barefootzero** » Thu Oct 08, 2009 11:24 am

Concerning grounding. the most important concern is safety. With an ordinary system that has a internal PSU, an internal fault in the PSU could result in the rest of the metal case being live at 120V or 240V depending on your country. To prevent this they put in a grounding wire which connects the body of the suply and by extension the case to ground so if there is a short to the case it will short to ground and the user will not get shocked.

If you are using a external brick this is not a problem as the output voltage of the brick is relatively low so you don't have to worry about getting shocked. Your brick probably has a 3 pin power plug for the reasons mentioned above. It all comes down to the question of "how much voltage is going into the box" and "will that voltage kill someone if they touch it."

I am not sure why some products are not required or do not have three pin connections. Perhaps someone decided the risk of a user contacting high voltage was very low in those cases.

taidi · Post by **taidi** » Fri Oct 09, 2009 6:56 am

Thanks for the clarification - I wasn't thinking straight;

laptops obviously don't require a path to ground when running off the mains via the charger.

I've been playing with Antec's Power Supply Calculator

http://www.antec.outervision.com/PSUEngine.

and it advises 128 watts with no video card selected. Deselecting the DVD writer reduces this to 98 watts - is 30 watts a typical figure for a DVD writer ?? I seldom use it anyway.

I'm thinking a PicoPSU-150-XT plus FSP 12V 150W AC/DC Adapter would power the system OK but all the FSP power bricks seem to use a fan for over-heat protection.

Also, I noticed on another thread that the 2.5mm barrel type power connector might not be adequate for a power brick of this capacity (12.5A according to spec) - has this been resolved ?

barefootzero · Post by **barefootzero** » Fri Oct 09, 2009 9:08 am

I can give you my system for comparison.

MB: 785gm-e65
CPU: Athlon II x2 240
Ram: 2x2GB DDR3
HD: 2.5" Fujitsu 120GB IDE
DD: Sony Blu-Ray Drive (full sized)
PSU: Electrodacus's 130W DC-DC adapter with salvaged 90W 24V NEC brick.

Power measured at outlet using Seasonic Power Angel.
Max (Prime95 + Furmark+3.5" HD) 85W
Min (idle or web browsing): 33W
Bioshock: 65W

Sense then I have added a XiFi PCIe soundcard but I have not measured again yet. Using the 2.5" HD saved about 5W but that HD 3.5" was pretty lousy. Much better ones are now available.

You can find electrodacus on these forums and he sells his adapter on e-bay. Because his PSU runds off between 18.5-25V it is much easier and cheaper to find a brick that will work and is fanless.

What I did was build my system and use an old PSU first to check power consumption then once I determined what it needed I got the smaller PSU.

mark19891989 · Post by **mark19891989** » Fri Oct 09, 2009 11:32 am

here is my htpc for comparasion:

motherboard Asus P5KPL-AM iG31
CPU: E5200 @ stock vcore
HSF: mini ninja
RAM: 4gb ddr2 800
HDD: Hitachi DeskStar 1TB 7200 (not very quiet replacing asap)
GPU: GeForce 7300 GS
PSU: picopsu 150XT + Dell DA2 220W
DVD: standard full size drive, dont use it often.
power consumption
Idle: 45W

usage:
Playing 720p video: 50w

watching a 720p video a few torrents and mprime on both cores: 80w

taidi · Post by **taidi** » Fri Oct 09, 2009 12:07 pm

Thanks...those comparisons look encouraging. I have found a couple of fanless AC/DC converters from a UK company which should work with the PicoPSU-150; 150W and 180W - I'll call them Monday.

http://www.relec.co.uk/product743.html

http://www.relec.co.uk/product744.html

Oops....that should be 180W and 200W !

piglover · Post by **piglover** » Fri Oct 09, 2009 12:51 pm

taidi wrote:Thanks...those comparisons look encouraging. I have found a couple of fanless AC/DC converters from a UK company which should work with the PicoPSU-150; 150W and 180W - I'll call them Monday.

http://www.relec.co.uk/product743.html

http://www.relec.co.uk/product744.html

Oops....that should be 180W and 200W !

They both use Mini-DIN power connectors. You'd need to do a small mod on the Pico-PSU side to accept it, or use an adapter cable. Not a big deal.

barefootzero · Post by **barefootzero** » Fri Oct 09, 2009 6:29 pm

piglover wrote:
taidi wrote:Thanks...those comparisons look encouraging. I have found a couple of fanless AC/DC converters from a UK company which should work with the PicoPSU-150; 150W and 180W - I'll call them Monday.

http://www.relec.co.uk/product743.html

http://www.relec.co.uk/product744.html

Oops....that should be 180W and 200W !
They both use Mini-DIN power connectors. You'd need to do a small mod on the Pico-PSU side to accept it, or use an adapter cable. Not a big deal.

If I recall correctly the Pico-PSU has a 4 pin connector like is used on a P4 plug with an adapter that converts to a barrel connector. He could take the adapter and cut the barrel connector off, cut the connector off the PSU and soulder the 4 pin plug from the adapter in its place. This would be good as the barrel connector isn't rated for the current the PSU draws at full load anyway.

taidi · Post by **taidi** » Sat Oct 10, 2009 1:33 pm

Mini-box.com ship their 150W adapter with one of these...

http://resources.mini-box.com/online/PW ... -5A-b1.jpg

I'm sure I couldn't fabricate that even if I could get hold of the connectors

But I shall ask Relec if they can provide the same.

taidi · Post by **taidi** » Wed Oct 14, 2009 7:50 am

I finally got some power readings for my system.

Boot, peak watts = 80
Idle, watts = 65 (53 with C&Q running)
Running Linx 0.63 using all spare memory, peak watts = 92.
I ran this until the CPU temp stabilised and then gave it another five minutes - about 15 minutes altogether.

Out of interest I also checked a couple of routine tasks...

Copying a CD using Nero, peak watts = 80
A large back up to an external USB powered laptop drive, peak watts = 80
Defrag of system drive, peak watts - 75

Before I started the PC I was surprised to see it was pulling 10W from the wall socket, - would this be the power supply ?...and is it an overhead I can discount with a Pico PSU ?

So far it looks as though I could comfortably power this system with a 120W Pico PSU......but have I missed anything ?

reddyuday · Post by **reddyuday** » Wed Oct 14, 2009 9:13 am

taidi wrote: Before I started the PC I was surprised to see it was pulling 10W from the wall socket, - would this be the power supply ?...and is it an overhead I can discount with a Pico PSU ?

So far it looks as though I could comfortably power this system with a 120W Pico PSU......but have I missed anything ?

We shouldn't take these power readings too seriously. I was assuming that the little watt meters that we plug into the wall sockets were good for measuring the power draw accurately. But they are not. It appears that the 10W idle power draw is bogus. Secondly, the watt meter is probably not able to detect the high speed peak draws that computers do. So these readings are only a rough approximation of sustained power draw. Thirdly, the PC takes power from three separate voltage rails and each of them should have enough power. You can look at the doveman's old thread that I bumped this afternoon for some of the complexities.

I think you would be better off with a PicoPSU-150-XT as you originally planned, not 120W.

taidi · Post by **taidi** » Wed Oct 14, 2009 12:41 pm

reddyuday wrote:
I think you would be better off with a PicoPSU-150-XT as you originally planned, not 120W.

There isn't much difference in the cost so I shall settle on the 150w version.

I figured out what the 10W draw was - I have a little USB battery charger plugged into one of the rear ports via an extension cable which works even though the PC is shut down.

Hope you'll post your findings when yours arrives.

barefootzero · Post by **barefootzero** » Thu Oct 15, 2009 9:57 am

reddyuday wrote:
taidi wrote: Before I started the PC I was surprised to see it was pulling 10W from the wall socket, - would this be the power supply ?...and is it an overhead I can discount with a Pico PSU ?

So far it looks as though I could comfortably power this system with a 120W Pico PSU......but have I missed anything ?
We shouldn't take these power readings too seriously. I was assuming that the little watt meters that we plug into the wall sockets were good for measuring the power draw accurately. But they are not. It appears that the 10W idle power draw is bogus. Secondly, the watt meter is probably not able to detect the high speed peak draws that computers do. So these readings are only a rough approximation of sustained power draw. Thirdly, the PC takes power from three separate voltage rails and each of them should have enough power. You can look at the doveman's old thread that I bumped this afternoon for some of the complexities.

I think you would be better off with a PicoPSU-150-XT as you originally planned, not 120W.

What is your reasoning behind thinking they are not accurate at measuring average power consumption?

I am inclined to believe the numbers mine gives and I have compared it in the high end using a true rms current and volt meter. Of course I was not able to measure power factor that way but the unit says my PF is almost 1 and the current and voltage readings seam accurate. My current meter is not accurate enough below 0.1 A to make a good comparison so I suppose it might be less accurate down there but I don't have any reason to believe that.

I don't really care if it is averaging over a little bit of time to give me power draw. It is not actually "missing" it so much as averaging over a practically useful length of time. If the display was constantly jumping all over the place it would not be helpful and if it read the peak instead of average it would also not be useful for what it was designed. It is my belief that a good brick designed to handle computer use should be able to handle any very short spikes if they are typical in that environment.

reddyuday · Post by **reddyuday** » Thu Oct 15, 2009 12:08 pm

barefootzero wrote: What is your reasoning behind thinking they are not accurate at measuring average power consumption?

Oh, they are probably ok for measuring average power consumption. But I am not confident that they do a good job of measuring the peak power draw, which is what we need to know to decide the capacity of the power supply.

I had bad experience with PW-200-V which, coupled to an FSP 150W power brick, couldn't power a system that according to Brennenstuhl was drawing a max of 112W. I should admit that I didn't get to the bottom of the discrepancy because I needed to get on with things. But I was warning taidi not to go strictly by what the power meter says because it may not be accurate enough to display the peak draws. Do you think that 120W would be enough for his system?

electrodacus · Post by **electrodacus** » Thu Oct 15, 2009 4:20 pm

The 10W power consumption is from the 5V standby usually this 5V standby is not very efficient is in the range of 50 to 70% efficient and the 5V standby also supply the USB posts when computer is power down. So the 10W power consumption is normal.
Peak power is not important if is under hundred of ms and not registered by the power meter but is important to know the individual line power consumption especially the 12V and 5V line on most picoPSU including the PW-200-V the max load on 5V line is 6A and this is usually not enough on some systems.
I do not know if the picoPSU will work with your system because I do not know the power draw on 5V line but if it will work it make no difference if is PicoPSU 150 or 120 they will both work or not depending on the 5V load.