Load shedding

A long Mars night, the panels damaged by the last storm. The batteries sink. Instead of waiting until everything fails at once, a good chip sheds the loads one after another – first the unimportant, last of all what keeps you alive.

Loads by priority#

With area power controls (yesterday) every area becomes a switch. You divide the base into priorities:

Life support does not hang on the chip at all. Whatever must never go off does not get a switch either.

Stages as the charge falls#

Each stage is the familiar pattern for a load that switches off below a threshold:

sge tmp level C_OFF   # still above the shedding limit?
and comfort comfort tmp
sge tmp level C_ON    # already above the reconnect limit?
or comfort comfort tmp

Three times in a row, just with other defines. Because the limits are staggered, the order comes about by itself.

Reconnecting with hysteresis#

Shedding lowers consumption, the charge recovers a little right away. Without a gap the area would come straight back on, then off again – every other second. That is why each reconnect limit lies clearly above its shedding limit. And because the reconnect limits are staggered too, the most important comes back first.