Isolation Problem

[Sceptre]

i have designed an aluminum case for a project i'm doing and I have two power supplies within that case. I have a computer PS to allow easy plug-in, and it had all the voltages I needed. and I also have a 48vdc power supply. The problem is, the case of the computer PS is earth ground, and the case of the 48v supply is negative. this is causing me some problems, mostly with safety.

is there an easy, and safe way to get around this? what would be the downfall of simply removing the earth ground from the PC PS and not grounding the complete unit? its a little harder to remove the grounds from the case as they have to be mounted in with screws/bolts

anyone have an easy way around this? or a way to mount the case without making an electrical connection (maybe inserts of some sort)?

any info would be greatly appreciated.

 

[Nigel Goodwin]

Without knowing many more details it's hard to comment, but I would suspect it should be fairly easy to disconnect the -48V connection from ground in that power supply. There's no need for the secondaries to be connected to ground - and a single supply will probably be easier then the multiple PC supply.

 

[ChrisP]

Of course, as you already surmised, a simple solution would be to mount the 48VDC supply to the project box using insulated standoffs. There are several alternatives available, from nylon screws, nuts, and spacers right up to Bakelite standoffs with threaded inserts.

For example, in the USA, Radio Shack has their P/N 276-1381 -- a set of four 10mm-long insulated standoffs complete with screws and lock washers...