Barton C Massey wrote:
> None of which (excepting 2a, which is perhaps a big deal,
> but I'm having a hard time imagining this being that hard to
> get solid) suggests to me that we shouldn't supply both raw
> battery voltage *and* usb-ready +5V to the nodes, since
> we're using a non-standard connector anyway.  I don't see
> the extra pair of wires as a huge drawback, and this would
> allow devices to choose what they needed.  In particular,
> this would let the microcontroller run off USB power, which
> means that groups like PARTS could reuse our layout and PCB
> for the microcontroller half-board as-is.
> Am I missing something?

Just a nit-pick.  :-)

The argument given for item 1 was a bit fallacious.  If it takes (for 
instance) 2W to run a transmitter and you supply 5V to it, then you will 
be obliged to reduce its resistance enough to draw 400 mA to run it.  If 
you supply it with 12V, then you only need 167 mA to get the 2W output.  
The 14 V wiring  could actually be smaller (and hence lighter) than for 
the 5V. 

I completely agree with your reasoning that two sets of wires is a good 
solution.  I don't see building a voltage divider circuit (to give 5V 
from the 14 wiring) as cost effective or weight effective.
Richard Johnson
not doing much, but still reading the mail.

psas-avionics mailing list

Reply via email to