dedicated fan/lights PSU

[honegod]

for fun, while building my computer, I decided to run all four 120mm case fans with a second powersupply.

I used an old fulltower AT case, which has a [H]uge powersupply case with lots of room for two modern supply boards so I filled it up with a 350w sparkle for the motherboard and drives, and a 250w AT from an old case for the fans.

I rigged a relay to switch the ground of the fans between ground and 5v+

when I first switched the fans to 7v (5v ground) only two of the four fans would run.

I had learned that the powersupply will want a load on the 5v rail so I had a couple 6v dash light bulbs running to provide the load. adding 3 more got the other two fans running @ 7v.

sweetness.

after about 100~200 hours of running, mostly at 7v (it is much quieter at 7v :D )
the fan supply stopped working.

it was an OLD psu, so it might well have simply reached the natural end of its life, what I fear is that I stressed it abnormally with the wierd grounding of the fans.

I need to replace the AT psu, I have several old boxes with psus that I can use

BUT I don't want to have to repeat the procedure every 200 hours ( adapting the psu involves a fair ammount of soldering )

is there an obvious error I am making here that has escaped my notice ?????

[Vertigo Acid]

Yes, you have made a mistake. There is no reason to put in a second power supply just for lights and fans. But, if you really want to do it again, I would suggest something besides small light-bulbs as load, because they really don't pull enough to keep the PSU in regulation, hence the death from non-load you may have experienced. I do question whether it has died or not tho.

[honegod]

Yes, you have made a mistake.

naturally, but exactly what ?


There is no reason to put in a second power supply just for lights and fans.

depends, eh ?
I had onhand a mid power sparkle, and a spiffy new raid motherboard with 8 drive slots for me to fill, so it seemed reasonable to just run the drives and processor and motherboard and video off the 350w, not overburdening the capability of the nice PSU.

since I have several old AT cases, with PSUs it seemed most reasonable to use one for the fan array, plus I wanted a engraved window, with the engraving lit, no reason to load the computer PSU with all that draw.

600w of available power, at the cost of a bit of soldering.


But, if you really want to do it again, I would suggest something besides small light-bulbs as load, because they really don't pull enough to keep the PSU in regulation, hence the death from non-load you may have experienced.

reasonable, I had a bad time finding big 6v DC bulbs and sockets to fit them so I used several of the little units I found.
I didn't want to just stuff a resistor inline and have a pure heater in the case, I was rather pleased at what I came up with to use the light from the bulbs while ducting cooling air across the bulbs and out of the case WITHOUT letting any of the light escape but to where I wanted it. {making the window engraving glow.}



how many amps/watts @ 6/5v worth of bulbs do you figgure I should run to be safe ???




I do question whether it has died or not tho.

I turned on the main power switch, the cases stock AT power switch which passes AC wall current to both PSUs, the fans and lights didn't come on, I failed to notice as I was busy at the moment.
I turned the key which turned on the motherboard and booting commenced normally.

as the bootscreen was doing its thing I noticed that my remote thermometer was indicating the CPU temperature was abnormally high and rising.
got to the desktop and MBM said the CPU temp was abnormally high, and rising.

I stopped being busy with other stuff and kicked the fans to 12v, and it DIDN'T WORK !!

the fans failed to get loud, so I looked at the window and it was not lit.

I clicked the start/shutdown button and watched the thermometer start dropping.

I tried the power switch a few times but nothing came on.



so, I got AC power through the switch to the motherboard/drives PSU.

I solder well, so the fans/lights PSU is getting power, but nothing is coming out.


how should I check the AT PSU ????

[Format _C:]

Instead of lights use a coupple of 25 Watt 5 Ohm power resistors

[Vertigo Acid]

Lights and fans do not draw enough power to make it worth a seperate power supply. How many drives you do have? The mistake you made was putting all the fans and lights on one supply, that draw <60watts combined, and all of the high draw things on the other supply, mobo/cpu/drives that draw >60w. If you must use two PSUs, spread out the load more evenly.

[honegod]

Lights and fans do not draw enough power to make it worth a seperate power supply.

but it's FUN !
I had that great big fulltower AT powersupply box, and two moderatly powered supplies that would BOTH fit in it.
why NOT fill the box with all the power I can ?
overkill for future coolness demands


How many drives you do have?

the motherboard has onboard raid, I plan to use up most of the 8 available drive plugs, eventually. :D




The mistake you made was putting all the fans and lights on one supply, that draw <60watts combined, and all of the high draw things on the other supply, mobo/cpu/drives that draw >60w. If you must use two PSUs, spread out the load more evenly.

it seemed a logical division of the electron flow, both the fans and lights are isolated from case ground so any noise they might induce into their power flow should be isolated from the data power.
silly, but I liked it.

[honegod]

Instead of lights use a coupple of 25 Watt 5 Ohm power resistors

I found a couple toyota taillight bulb sockets that take 25 watt 12v bulbs,they had no ground wire so I soldered some on.

I made a mount out of 1/2" closed cell foam sheet to hold them above the cd recorder at the top front of the case.

I wired them in parallel with the window lights.

with the case cover on, the buttons glow really faintly, otherwise there is no light leakage.

the airflow through the buttons { pressurised case, air leaks blow out} seems to keep the temperature from building up because of the bulb heat.
I have noticed NO change in powersupply output air temperatures

so my thinking is that the 12v bulbs HAVE resistance, and two of them, in parallel, should have a power draw something along the lines of one 25watt 6v bulb.


I yanked the 200w AT supply that din't work and adapted in a 250w sparkle AT from another dead antique.

so far I have no balls to run it @ 7v, although a brief test showed it working fine