标签: power cycling

We recently lost electricity at the house. I am sure this an experience you have all had. When the power came back on a few hours later (what a relief), it was as if the house had come alive—both figuratively and literally. I say this because as power came back, there were all sorts of "hello, I'm here" beeps and sounds emanating from every corner, from the PCs, the printer, the cordless phones, the TV, the VCR (yes, we still have that!), the answering machine, the microwave, the stove, the cable modem, various clocks, and more. It was as if each of these had just been born, and was demanding parental attention. And some of them really needed it: there were clocks to reset, PCs to reinitialize, settings to restore; the list went on. As I went around taking care of them, all I could think of was Mary Shelley's classic book Frankenstein where the protagonist of the title creates artificial life, who we have come to know as the "monster" (don't want to read the book? You can also enjoy the classic 1931 movie version with Boris Karloff). There's an eerie parallel between the house's awakening and the monster's: in the book, the monster is brought to life by a bolt of lightning which comes from a rod on the roof to the lab where the experiment is under way. Sounds sort of like having the AC mains come on, in a way.... The AC-power cycling was like a creature coming to life, for sure. But it also reminded me that engineers should fully, thoroughly exercise and verify random power-off/power-on cycling of their products for every operating mode and scenario. Most of us have seen products which crashed when power failed, and had to be manually power-cycled few times to restart them—and have even seen some which failed outright when the power failure or restart occurred at just the wrong moment. So I'll deal with my personal "creature" coming back to life, and you can help by doing thorough job of designing and checking the cycling of the ones with which you're involved, please. Even if your product has a back-up battery, it too can run down, of course, or need special consideration. Have you ever experienced "bad behavior" due to random power cycling?

Recently, we lost electricity at the house, an experience I am sure you have all had. When it came back on a few hours later (what a relief), it was as if the house had come alive—both figuratively and literally. I say this because as power came back, there were all sorts of "hello, I'm here" beeps and sounds emanating from every corner, from the PCs, the printer, the cordless phones, the TV, the VCR (yes, we still have that!), the answering machine, the microwave, the stove, the cable modem, various clocks, and more. It was as if each of these had just been born, and was demanding parental attention. And some of them really needed it: there were clocks to reset, PCs to reinitialize, settings to restore; the list went on. As I went around taking care of them, all I could think of was Mary Shelley's classic book Frankenstein where the protagonist of the title creates artificial life, who we have come to know as the "monster" (don't want to read the book? You can also enjoy the classic 1931 movie version with Boris Karloff). There's an eerie parallel between the house's awakening and the monster's: in the book, the monster is brought to life by a bolt of lightning which comes from a rod on the roof to the lab where the experiment is under way. Sounds sort of like having the AC mains come on, in a way.... The AC-power cycling was like a creature coming to life, for sure. But it also reminded me that engineers should fully, thoroughly exercise and verify random power-off/power-on cycling of their products for every operating mode and scenario. Most of us have seen products which crashed when power failed, and had to be manually power-cycled few times to restart them—and have even seen some which failed outright when the power failure or restart occurred at just the wrong moment. So I'll deal with my personal "creature" coming back to life, and you can help by doing thorough job of designing and checking the cycling of the ones with which you're involved, please. Even if your product has a back-up battery, it too can run down, of course, or need special consideration. Have you ever experienced "bad behavior" due to random power cycling?