Date: Fri, 06 Mar 1998 20:34:07 -0800 (PST) From: Simon Shapiro <shimon@simon-shapiro.org> To: Mike Smith <mike@smith.net.au> Cc: Chuck Robey <chuckr@glue.umd.edu>, Terry Lambert <tlambert@primenet.com>, dmlb@ragnet.demon.co.uk, wilko@yedi.iaf.nl, julian@whistle.com, chat@FreeBSD.ORG, lada@ws2301.gud.siemens.at, Karl Denninger <karl@mcs.net> Subject: RE: Old farts blathering (was Re: SCSI Bus redundancy... ) Message-ID: <XFMail.980306203407.shimon@simon-shapiro.org> In-Reply-To: <199803070413.UAA02168@dingo.cdrom.com>
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On 07-Mar-98 Mike Smith wrote: > > Where I come from we shoot people like this before they get started. > The last time I had to put up with this, the geezer in question was > busy trying to explain how resistors were more vulnerable to static > electricity than capacitors. I see from the below, you have very little trouble joining in :-) >> >From R/C car racing, a sub-c NiCd battery will put out 60 AMp for about >> >3.5 >> minutes. > > That's 3.5Ah, which is substantially beyond the capacity of a "sub-c" > NiCd cell (usually around 1.1Ah until quite recently). In reality, > that sort of discharge rate will cause electrolyte depletion and > self-regulation after a few seconds, although even then in older cells > there's room for the sucker to pop on you. I thought so too. First, the cells are nominally 1,700MaH, then the chargers are really tricky, then the batteries have the life expectancy of an NHRA funny car engine, then they get hot enough during a run that you cannot solder the tabs, they must be welded, or the pack will fall apart, then the cells must be one particular Sanyo model. If not, all that you said happens. Quite amazing. > DC-is-better-than-AC is a comfortable myth with a grounding in FUD and > a fertile ground in the not-so-well-informed minds of Telco engineers. Yup. We are back to Edison-vs.Tesla all over again :-) > Some contributing factors to this have historical validity, but most > are overwhelmed by the drawbacks of low-voltage DC. IIR is not your > friend. > > And just harking back to Karl's earlier comments inre: AC:DC vs. DC:DC > conversion - AC:DC conversion these days *is* DC:DC conversion, and a > TL437 and some garden-variety magnetics will give you better power than > you might want to believe. > > You have to be outrageously stingy to produce rotten DC these days, or > just obsessed with doing it the hard way. (Of course, PC manufacturers > are typically outrageously stingy...) Yup. The WDT board I am polishing the driver for alarms for low-voltage on a new, EXPENSIVE, rackmount CPU box. No, the WDT is not broken, but the 5V is really 4.73. You are right, you have to try hard to mess up... ---------- Sincerely Yours, Simon Shapiro Shimon@Simon-Shapiro.ORG Voice: 503.799.2313 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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