What you learn today
- Emergency mode instead of standstill
- Switch off partial functions
- Return
The CO₂ sensor in the living module fails. What should the filtration do? A cautious chip switches everything off because it does not know anything any more – and after an hour the air runs short. A good chip keeps working, just differently.
Emergency mode instead of standstill
Think about every sensor: what is the most sensible operation without it?
| Failure | Emergency mode |
|---|---|
| CO₂ sensor | filter runs all the time – costs power, but the air stays good |
| temperature sensor | heater off, warning on |
| airlock pressure sensor | doors closed, no pump |
| battery reading | comfort loads off |
The emergency mode is worse than normal operation, but better than nothing at all. And it is visible: a display or a flashing light says that things are not normal right now.
Switching off partial functions
Not everything is equally important. Decide on an order: air before light, light before workshop. If power gets short or the filter runs at full load in emergency mode, the unimportant loads leave the grid first. Life support stays until the very end.
Returning
When the sensor comes back, the chip should work normally again – but not on the first valid value. A loose data cable would otherwise switch between normal and emergency mode every tick. That is why the chip counts how many passes in a row the value was valid:
snanz tmp co2
add good good 1
mul good good tmp # invalid value: back to 0
min good good STABIL
sge normal good STABIL # only after STABIL good passesA single invalid value resets the counter. Only after three good passes does “normal” apply again.
The same counter also gives you a gentle start: right after inserting it is at 0, so the chip begins in emergency mode and only switches over after a few ticks. Better to filter a little too much than once too little.
Exercise
Task
The filtration “Luftfilter” runs normally by CO₂ (sensor “Luft”): on above 1 %, off below 0.5 % – switched as always via On and Mode. Without a valid CO₂ value it runs all the time (emergency mode), and it only returns to normal operation after 3 valid passes. The light “Komfort” switches off below 20 % battery (battery “Akku”) and back on from 30 % – and is always off in emergency mode. The display “Betrieb” shows 0 for normal and 1 for emergency mode, the flashing light “Notbetrieb” is lit in emergency mode.
Hints
Hint 1
The counter: add good good 1, then mul good good tmp with tmp = snanz co2, then min and sge normal good STABIL.
Hint 2
Compute the filter with hysteresis first, then select filter normal filter 1.
Hint 3
Comfort with hysteresis as in load shedding, finally and comfort comfort normal.
Quiz
4 questions. You pass from 60 % – the server does the grading.
Complete the day
- Passed the simulator exercise
- Passed the quiz with at least 60 %
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