[Server-devel] smooth shutdown for 12V-DC powered XS

Kévin Raymond shaiton at fedoraproject.org
Thu May 10 05:10:43 EDT 2012

> Yes, nice aren't they?  I would not use Arduino where power was
> critical.  I had assumed that since a server was involved, one more
> device wouldn't stretch the power budget that far, especially given
> the benefit that voltage monitoring brings.

Oh yes, we will have a fitPC2 and a dreamplug (not sure, this one
could be merged on the XS if it has a WIFI AP).
It is just to design something best.

>> I still think that building our own board could be better as it will
>> be smaller and more robust (no unuseful I/O, no wasted components???)
> If you wish to lower cost and size, and do not need a log of voltages,
> then consider avoiding a microcontroller altogether; use a comparator,
> a reference voltage, generating a "voltage is low" output, that can
> then be fed into a serial port modem control pin, or drive a relay
> that briefly presses the power button on the server.

Yep that was my original plan, but already designed the backup plan.
I'll see if we have an analog input available.
Oh Xavier, I see that the XS has only one mini-DVI output display… Do
we have an adapter? (only for debug, of course).

>> >
>> > I suggest a 100k potentiometer with a 1uF capacitor.
>> I would prefer to choose only resistances, not potentiometer, as
>> people won't try to change settings! (And the threshold would be
>> updated on the host software).
> In that case, I recommend a three-fold divider, so that 15V is
> translated to 5V.  50k resistor to ground, 100k resistor to input
> voltage, common to analog input.
> I would use a potentiometer, then glue it down, or cover it up.

Ah ah, yes.

>> I need to catch the right tty port, and be sure to handle
>> connection/reconnection???
> My point about using /dev/serial/by-path is that you don't need to
> worry too much ... just label the port as dedicated to that purpose.


Kévin Raymond

More information about the Server-devel mailing list