Subject: Re: serial port control
To: None <current-users@NetBSD.ORG>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
Date: 02/18/1998 14:41:45
> Its not clear to me yet that sine wave output wins. Square wave
> should be more efficient since you don't have the big dead-time
> between, the two peaks.
Of course, it depends on what you're feeding; I certainly wouldn't want
to drive a normal incandescent lightbulb, since the effective RMS
voltage will be well above what such a bulb is designed to handle. I
don't think trying to run a room light off the UPS is unreasonable;
perhaps you disagree. :-)
> If the load is your typical PC switching power supply then it would
> really prefer to have the full ~170v peak voltage applied all the
This all *sounds* very reasonable.
However, just recently I had occasion to inspect two power supplies
taken from disk enclosures. They didn't have killer transformers on
them, but they also weren't multiple-hundred-watt power supplies. I
followed the etch runs (single-sided pc board, y'know, piece of cake to
trace) and line voltage fed directly into *something* inductive. I
didn't take an ohmmeter to it to determine whether it was a normal
transformer or co-inductive chokes in series with each wire...but
either way, feeding it anything with sharp edges is not going to keep
If you're really that sure what you're feeding is as you describe, why
not just feed it 170VDC and be done with it?
> It just doesn't pay to round the corners of the wave unless one is
> running a motor or transformer or something like it that will get
> very upset at the high dv/dt of the square waves.
...or something like an incandescent light bulb that will get upset at
the higher V RMS even though the V P-P is the same as line voltage.
No, I want at least approximately sine-wave output for anything I can
just plug regular line cords into. (If it's closely coupled with the
machine's power supply, sure, do anything that's convenient.)
Of course, I also want continuous conversion, not cutover. :-(
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