Hello respected engineers! I've built myself a frame where I've put six hard disks for a RAID5 system, and six 8x8 cm fans to cool them down (they live in a quite hot environment!). The PSU is a 500W one however I was concerned that the fans may pollute the hard disks' supply too much.. since they're motors after all! I've accidentally put a finger into a fan (what a pain!), and this stopped the fan for a moment and also caused hard disk errors, and thus convinced me even more that I need to decouple the fans' motors supply from the hard disks supply.
But how? I'm just a hobbyst when it comes to electronics, so I may even intuite correctly, but I won't be really sure of my thoughts. Right now, they are that I need some big inductors (with as low DC resistance as possible), some (big?) capacitors and maybe also a big rectifier as well.
The best scheme I've thought so far is to link all 6 fans together in parallel, then apply power through a circuit like this:
6 fans--*-ind-*-ind-*-ind-*-ind-*-ind-*-ind---diode------*-----PSU +12V | | | | | | | cap cap cap cap cap cap 6 HDs---PSU +5V | | | | | | | Gnd ----*-----*-----*-----*-----*-----*------------------*-----Gndof course in the above scheme I don't even need them to be six, it's simply the more the better, I just happened to have six of them on my bench (more or less a coincidence).
But now the big question: what's the right size of the caps, also to not overload the PSU at start? Will the diode really help the hard disks to not get some bad bad bad back EMF? Notice also that the wire that feeds the fans is AFTER all the wires that feed the hard disks (otherwise the voltage drop caused by the fans would have affected the hard disks). Yes, at least I know this. ;)
Is my scheme ok? What can I do to improve it? I really care about the hard disks and the data they contain!
Thank you very much, Mike