4 ms·

Synchronizing phase, and/or hitting that switchover window is trivial for even the cheapest microcontroller. One cycle at 60Hz seems fast but its an eternity fo

Synchronizing phase, and/or hitting that switchover window is trivial for even the cheapest microcontroller. One cycle at 60Hz seems fast but its an eternity for a 20Mhz uC. I'm going to guess "detects the drop and hits the window" simply because this is how cheap UPS units work and I'd bet a month of lattes that its made of cheap UPS guts.

andrewcooke 17y ago
can you explain how synchronizing phase is trivial? the previous post made sense to me. it is hard to shift phase. i agree that you could not try, and instead "hit the gap" (in which case synchronizing phase isn't important), but if you don't do that, and instead want to connect two supplies at once, how does a microcontroller make that easy?
- nearestneighbor 17y ago
  Firstly, you don't need to phase shift here, because you'll need to generate AC from DC (battery), so you may as well generate it in phase with the signal from the outlet. Secondly, if you need a phase shifting device (for something else), depending on the requirements, there are a number of options starting with something as simple as an RC unit. Thirdly, generating "AC" [periodically changing signal] of a given voltage and an (approximate) frequency in sync with some other signal is what CRT TVs did (for the CRT). > it is hard to shift phase. Not to the engineers building these kinds of devices (I'm explaining high school to freshman Physics here)
  - andrewcooke 17y ago
    maybe instead of explaining the obvious you should read the original comments. the comment i was defending was about converting ac to ac. their conclusion was that it would need to go through dc (which no-one, including me, has disagreed with).
teuobk 17y ago
Yes, 20 MHz is a higher frequency than 60 Hz. While that would help for the sensor version of the design, it would not directly help for the synchronization of the AC sources. It might help you while building a switching supply to do the AC to DC conversion, and it could help when approximating a sine wave on the DC to AC conversion. Still, all of that is quite a bit more complicated than just quickly switching in a new source when the other source drops out. (Credentials: I'm an electrical engineer and have designed and built power supplies.)

andrewcooke 17y ago

can you explain how synchronizing phase is trivial? the previous post made sense to me. it is hard to shift phase. i agree that you could not try, and instead "hit the gap" (in which case synchronizing phase isn't important), but if you don't do that, and instead want to connect two supplies at once, how does a microcontroller make that easy?

nearestneighbor 17y ago
Firstly, you don't need to phase shift here, because you'll need to generate AC from DC (battery), so you may as well generate it in phase with the signal from the outlet. Secondly, if you need a phase shifting device (for something else), depending on the requirements, there are a number of options starting with something as simple as an RC unit. Thirdly, generating "AC" [periodically changing signal] of a given voltage and an (approximate) frequency in sync with some other signal is what CRT TVs did (for the CRT). > it is hard to shift phase. Not to the engineers building these kinds of devices (I'm explaining high school to freshman Physics here)
- andrewcooke 17y ago
  maybe instead of explaining the obvious you should read the original comments. the comment i was defending was about converting ac to ac. their conclusion was that it would need to go through dc (which no-one, including me, has disagreed with).

teuobk 17y ago

Yes, 20 MHz is a higher frequency than 60 Hz. While that would help for the sensor version of the design, it would not directly help for the synchronization of the AC sources. It might help you while building a switching supply to do the AC to DC conversion, and it could help when approximating a sine wave on the DC to AC conversion. Still, all of that is quite a bit more complicated than just quickly switching in a new source when the other source drops out. (Credentials: I'm an electrical engineer and have designed and built power supplies.)