Re: connecting two 12V power supplies together

On Mar 6, 10:57 am, z <gzuck...@xxxxxxxxxxxxxx> wrote:
On Mar 6, 9:13 am, panfilero <panfil...@xxxxxxxxx> wrote:





On Mar 6, 7:58 am, "Greg Neill" <gneill...@xxxxxxxxxxxxxxx> wrote:

"panfilero" <panfil...@xxxxxxxxx> wrote in message

news:e0ee75d3-3cbd-40bd-9d21-d3effbc37083@xxxxxxxxxxxxxxxxxxxxxxxxxxxx

Hello,

I'm trying to figure out a way to have two power signals coming into a
circuit and the output remaining the same.... what I mean is that I
have two inputs where I need to connect 28V DC, and I should have the
same result whether only one of my 28V inputs is plugged in or both
are plugged in... I'm going to try and feed these inputs into a 5 Volt
regulator.... if I connect both the positive connections of these two
inputs into the regulator.... would that be ok?  Like connecting to
battery or power sources in parallel?  Something feels funny about
that to me... and I'm not sure if it makes sense to connect two power
sources together like that.... my gut is saying no.  But I'm not sure
why.

It's unlikely that both 28V supplies will be
precisely the same voltage (due to design
differences, component tolerances, etc.),  
thus you will end up with an undesirable
current loop between the supplies.

What is the purpose of having two 28V supplies?
Just to add current capacity?

I think that's what was bugging me... that the two power supplies
aren't going to be clean regulated 28V sources... so I'm a little
rusty on my electronics theory but there is something that leaves me
uncomfortable about doing that.... just connecting them in parallel
like that.  I'm thinking a Diode OR type solution would be the way....
basically I'm trying to pass the DC power on to somewhere else... but
the DC power may come from two different sources and either source (or
both) may be plugged in at any time, but I just need to pass that 28V
on through regardless of which source is connected.

much thanks- Hide quoted text -

- Show quoted text -

yeah, if you're not concerned about sharing the load equally so as to
maximize the output current available, just OR them and whoever's got
the most voltage will carry it; being off constituting a very low
output voltage.- Hide quoted text -

- Show quoted text -

DIODe Or Solution sounds best... the only con about using that is the
voltage drop across the diode, if at all possible I'd like to get the
whole voltage across...

much appreciate the responses
.

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