Functional Casemods?

attercoppe asks: "I'm looking for opinions and advice from Slashdot readers on a case mod idea. I'd like to install a second (small, low heat, no fan) power supply to run a single CD drive. The idea is to basically integrate a CD player into the case, allowing me to ditch my bookshelf stereo (yay convergence!). But I want to be able to use it without having the computer booted (to avoid waste heat and all the associated fan noise - PS, CPU, and two 4" fans). The question is, can I wire an existing drive, and maybe one of the supplemental fans, into both the existing and the new power supplies? Will one PS get feedback from the other through the drive? Do I need a switch to choose which PS to use? I know I won't be able to use the sound card... that's ok. No, I won't have a tuner for radio - that may come later. Tips, ideas, ridicule?"

Comments

No workie

[pbox]

Connecting outputs of two power supplies directly is a sure way of blowing up one or the other. Think about it this way: one is outputting 5.00V, the other one is 5.02V. You connect them together and the 0.02V difference will have to be resolved. The wires have negligable resistance (let's say 0.01 Ohm), so you will have (I=U/R) current that is 0.02 V / 0.01 Ohm = 2 A ! Doing nothing than disspicating from both PSUs. In real life 5V +/- 5% will give you 0.5 V max difference, and the wires are not much, so it will actually be likely to dissipate much more than my example.

You can connect diodes from both PSUs, pointing towards the CD, but the diodes have a 0.7V drop...

Or you can just buy that MSI barebones system, that already has the functionality that you crave...

Use the Goggle, Luke!