Hi, again -
I'm getting ready to commit to my new power scheme and before I start
drilling holes and spending money on wire, eurostrips, etc., I just
wanted to double-check my scheme with you all.
I've put up a PDF with a diagragm of what I'm tryin to do:
http://www.freeclyde.com//guest/FreeClyde_MOTM_Power_Scheme.pdfI've gotten some conflicting ideas about whether this is the right way
to fuse . . . . I've been told that the fuse in the AC input
connector is all I need, but I've also read that each power supply
needs a fuse after the switch as well.
The other issue I'm fuzzy on is tying grounds.
For the earth grounds to the power supply chassis: The most
convenient thing for me is to place one power supply right next to the
AC area (input connector, switch, and AC eurostrip). The other supply
would be 5-6 feet away. Should I a) just make sure the earth wires
from the AC terminal block to each of the chassis are the same length,
b) wire one chassis to the mains' AC earth and tie the two chassis
together, or c) something else altogether?
If it would be better for the power supplies to be next to each other,
that can be arranged.
Also, what about the two analog commons and the digital ground? Are
they all supposed to be tied together?
Last, I was told to use 12 AWG if I was going to daisy chain
distribution boards, but since I'm going to do a star configuration, I
should be OK with 14 AWG, right? The runs will be 2-4 feet (at least
if I separate the power supplies). Should I cut all the cables to be
the same length (from the power supplies to the distribution boards)?
Thanks for any thoughts! Sorry to newb out on you like this ...
- James
--- In motm@yahoogroups.com, "jamesabaxter" <motm@...> wrote:
>
> Hi -
>
> I've inherited responsibility for maintaining a >40 module MOTM.
>
> Paul advised me to ditch our Power One HDCC 150W (3A) in favor of two
> CP131As:
>
> 5VDC@8A w/OVP
> +/-15VDC@...
> Max Current/Fuse Rating 3A@120V
>
> I was hoping to get some guidance and reality checks before I get
> started . . . .
>
> First, fuses: I see that there is a 4A fuse in the AC input connector
> drawer. I plan to replace it with a 1.5 Amp fuse and do the same
> thing with another AC input connector for our second power supply.
> Does this sound right? Are these the only fuses necessary?
>
> Second, wire gauge: I understand that 12 gauge wire should be used to
> bring power from the supply to the distribution boards and to daisy
> chain other distribution boards. However, I notice that 18 gauge wire
> is being used to connect the AC input connector to the power switch
> and the power switch to the transformer on the power supply. I would
> have thought that 12 gauge wire would have been required there, as
> well. Is it not?
>
> Third, I understood from Paul that it would be OK to daisy chain the
> distribution boards as long as I use 12 gauge wire. We're talking
> 990, 960, and 900 on one supply, and a 960 & 900 on the other. From
> what I've been reading it seems it might be better to use barrier
> strips. Is this true? I don't really understand how this would work
> (I've never dealt with barrier strips) -- Is it sort of like a mult
> and works with jumpers?
>
> Last, just to double check: I wire to the terminals on the power
> supply that say +12V, -12V, +-RTN (for analog GND), 5V.RTN (for
> digital GND), and either of the +5V terminals. I ignore all the rest,
> which have 'S' in front of them (for remote sensing?).
>
> Thank you so much for any advice you can offer.
>
> - James
>