[time-nuts] 5370 processor boards available

[Chuck Harris]

That fix presumes that the power line never quits at
inappropriate times.  This winter has provided me with
ample reminders that power can go out anytime.

I think a better solution would be to find a very large
"super cap" and power the BBB from that while giving it
a power fail interrupt to quickly sync the file system.

-Chuck Harris

John Seamons wrote:
> On Feb 25, 2014, at 12:59 PM, John Seamons <jks at jks.com> wrote:
>
>> I may have a solution for the power-off problem that doesn't involve batteries
>> or supercaps. It has the added advantage of providing instant-on.
>
>> From the latest documentation:
>
> "One solution to the annoyance of having to halt the BBB before the instrument is
> powered off is simply to keep the BBB running by providing it a secondary source
> of power via the USB-mini port. The BBB already understands how to select between
> two sources of power: the USB-mini and +5V barrel connectors (the latter of which
> is actually being delivered from the 5370 via the board expansion connectors). The
> app detects when the instrument has powered down and resumes running when power is
> restored. USB power could come from an external USB hub or charger. You may have
> to obtain a longer USB cable than the one supplied. Be certain to only use the
> USB-mini connector that is adjacent to the Ethernet RJ45 connector. Do not use the
> USB-A connector on the other end of the board as that port will not accept input
> power.
>
> Some of you might even figure out how to derive +5V for the USB-mini cable from
> the 5370 oven power supply card that is always powered if the instrument is off
> but the line cord is plugged in. But beware of the potential problem of conducting
> noise from the BBB to the reference oscillator over such a connection. Some
> experimentation and measurement is necessary. The planned USB/Ethernet connector
> card that replaces the current HPIB one at the back-panel could host a voltage
> regulator. Aligator clip connections to the '+25V UNREG' and GND test points on
> the oven power supply would alleviate the need for any soldering."
>
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