Power Supply for PC

[mimosa]

Another layman question!

My PC has a bunch of stuff on it, and I want to add more. How do I know if the power supply can take it? Is there a way to calculate the power consumption of eg. HDDs, DVDRW, etc.? My unit has a 400W power supply.

[cmoszix]

P=VI where P is power (watts), V=voltage(volts) and I=current (amps).
Just add up and calculate. If u want, u should multiply by 0.8 for the rush current (P=V*I*0.8). But usually 400 watts should be enuf for the maximum stuff that can fit into your tower casing.

[mimosa]

Just read in yesterday's Star In-Tech that I need 700W above if I want to put in twin 7950GX graphic cards. Are there such power supplies with that rating in the local market?

[Firefly]

Not so sure about all the calculations. Firefly have a PC with 6 HDDs, CDRW and DVDRW. This does not include the 4 cooling fans...All Firefly did is add an extra Power supply. The extra powersupply is triggered by a 12v relay connected to the main supply's molex socket.

The main PSU (Power Supply Unit) powers the Mainboard and cooling fans. The secondary PSU powers all the drives.

There is only one problem, the secondary PSU cannot fit inside the casing. It sits behind. :eek:

[mimosa]

Ah, you must tell me more how to fix that. I have 2 HDDs (want to add 2 more), DVD, DVDRW, 6 cooling fans and 1 6600GT. Just how do I fix that relay external thingamyjig?

[blurrman]

Firefly have a PC with 6 HDDs, CDRW and DVDRW.

firefly, what interface are those hdd , cdrw and dvdrw using? sounds like u have a lot of things to store..

[Firefly]

Here is what I am doing. 4 HDDs are in RAID Strip & mirror. 2 are for storage. I dedicate the DVD writing to the DVD writer and CD to the CD writer.

The wiring setup it's simple. Any ATX PSU will have a big bunch of wires for the mainboard and 2 twin sets of molex for the HDDs and FDDs.

Picture of BTX and ATX PSU (http://www.overclockers.com/tips1137/)

This is how the connectors look like. The one on the right is the BTX and the one on the right is the ATX. Closeup picture (http://www.overclockers.com/tips1137/ps1.gif)


Get a 12 VDC relay. Assuming you have a spare ATX since the new BTX comes with your casing, If you were to short Pin 8 to any COM (Pin 3, 5, 7 15 17,18,19 or 24) the ATX goes on. Remove the wire from Pin 8 and connect to one of the contact points in your relay. and any of the COM to the other.

Connect the COIL of the 12V relay with the Molex connector (http://pinouts.ru/connector/4_pin_Molex_power_connector.shtml) Yellow (+12) and any of the other 2 middle one you get ground. So when you switch on your PC, the 12v becomes active powering on the relay. The relay NO (Normally Open) closes and switches on the ATX powersupply.

When you shut down your PC, the ATX shuts down at the same time.

Now for mimosa, you can power the Mainboard and Graphics card with the BTX PSU and the ATX PSU can power the fans and HDDs and everything else.

So imagine your BTX is 550W and the ATX is 500W !! you are now having a PSU that is 1050W!!!:eek: You can even power 4 X 6600GT..:D

Oh yes, if you cannot find a 12V relay, you can use a 6V unit then at the Molex connector, you use the Red (5V) and any of the 2 middle blacks.

[mimosa]

Thanks for the reply, but I must admit I'm :confused:.

On the other hand, I do have an old unused ATX PSU.
I just have to find out where to get the 12V relay VDC (vhatever dis cis) ... :confused:

[Firefly]

12 VDC realy...can get at any electronic shop or at car assoseries shop.
This is what I use. The relay (http://i23.ebayimg.com/03/i/07/41/16/9d_1.JPG) and the socket base (http://www.rpelectronics.com/Data/PYF08A.JPG)
The picture is a 240VAC. you just need to ask from an electronic parts shop for the type MY2 socket and base. Remember it's 12VDC.

You can actually use any PCU as the secondary PSU. Just require to know which is the triggering wire. AT type PSU you would be using 240V directly. :eek: connect that over the Normally Open terminals in place of the Signal/ Ground.