kablooey

[snip]

Except for the thieves ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

any buck-derived converter can over-voltage its output, if poorly designed. large L and small C means lots of overshoot when a large load (or worse still, overload) is removed, and there is not a damn thing the controller can do about it. At best the controller can add no energy to the output inductor, so all the energy stored there gets dumped into Cout. the cure is lots of C and not much L.

likewise a real slow controller and not much capacitance can also give lots of overshoot (undershoot, too), but that is easily fixed by choosing a higher closed-loop bandwidth.

Cheers Terry

...and hookers.

--
  Keith

Or a shunt regulator for such short-term events. And a crow-bar system... I did one years ago that had a circulating current of over

100A... fuse went like a flashbulb ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

Ain't that the truth. My wife took her troop to a Girl Scout convention up there a few years ago, and said the loitering around the hotels convinced her to never go to SF again.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

I did a 6-volt, 85 amp, three-phase [1] buck switcher for a CAMAC crate, a long time ago. I had to use a load dumper to meet the transient response specs, to gobble up the stored energy in the L's when the load dropped. It drew a couple of amps all the time, so it helped reduce noise and ripple, too. They show up on ebay now and then.

John

[1] this was a polyphase buck switcher, in about 1983. Anybody know of a previous example? Did I invent this? I *did* invent the dual-slope integrating A/D converter when I was a kid, but I wasn't smart enough to patent it, so Fairchild re-invented it and got all the money.

That's what happens in big city downtowns, what with the profusion of horny tourists with lots of time and money on their hands. Supply rises to meet demand.

I always suggest small hotels out near the ocean for my visitors... Ocean Park Motel, Robert's, or the Seal Rock Inn. They're way cheaper, neat, quiet, and you can walk on the beach or take a streetcar downtown any time you like. Seal Rock will give you an ocean-view room with a fireplace, steps from the Cliff House and the Land's End trails, for half of what you'd pay at the hideous Mariott downtown.

And don't even *think* about going to Fishermen's Wharf.

John

I'd be very surprised if any VME supplies+backplanes actually met this spec as stringently as you suggest.

Most of them will have no problem meeting that spec after startup with a fairly steady load. But most off-the-shelf linears are liable to bounce all over the place (at least +/- 0.5V) when driving a lumpy inductive backplane Vcc at startup. And switchers (which I'm guessing

95% of VME 5V supplies will be - I haven't seen that wasn't a switcher in the past 20 years) usually are a lot worse in terms of transient response.

What's strange is that everyone here is shocked, SHOCKED that backplane power supplies are this crappy. And then they go on to tell how much superior every power supply they ever designed is. Maybe I'm much more cynical but I can tell you that even for well-respected name-brand linear supplies, if you set the crowbar on the 5V line lower than 5.7V or so, it'll be tripping all the time with any real-world load!

Tim.

You mean, actually complied with the mandatory provisions of the IEEE spec? My customer tested crates from two other suppliers, and they do conform.

When I designed CAMAC crate power supplies, I actually read the spec and made sure I complied. And I did include a crowbar. If *** had included a crowbar set to even 7 volts, they would have promptly discovered the problem, before tens of kilobucks of gear was fried.

Roger the cynical.

John

Other than the times-square section of NYC and once in DC, I've never seen them as obvious as in NYC. In most cities the cops hassle em into hiding, at least.

Wher does the street car go, but the warf? I spent about a week in the financial district in the late '90s. My hotel was right at the top of the street-car run (can't rmember the name offhend, but it was one of the Holiday Inn group). The hookers didn't wander into the financial district but after dart they were thicker than flies a block away.

--
  Keith

Two of the three *cable* cars go near the warf. Take the Hyde street line, the most fun to ride, then walk around in Fort Mason, have an Irish Coffee at the Buena Vista to warm up, then ride back.

The *streetcars* go all over the place, including all the way out to Ocean Beach.

This is the Wild West. My new company building is just a few doors from The Power Exchange, one of America's biggest bondage and fetish establishments.

John

Ok:

I thought my hotel was at the top of the Hyde St. line (see above). It was a nice area, and the cable car (sorry) went down through Chinatown to the Warf. Again where else do they go? (see map, above). Don't get me wrong, I would have loved to have brought my wife along for that trip, but I really didn't know I was staying in the financial district.

Sorry. Ok, the *cablecars* go to hookerville. ;-)

It's wild, alright, but I think it's more NYC than anything I'd call "west".

Hey, I don't care what you do on your "lunch" break. ;-)

Honestly, I do like SF and I wished my wife would have been with me on that trip. It's a *great* place to visit[*], but...

[*] You have very intersting work, I'd love to try a hand at what you do, but SF isn't on the list of places to live. ...can't afford it.

--
  Keith

While it seems clear that the crate is out of spec, when is all said and done it seems likely to be a three way near tie on picking up the tab. likewise that crate vendor has likely seriously lost a customer whatever the outcome.

--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
--Schiller

nonsense, i would do it for 90e9 $ each, 30 second warranty. 10e6 $/m service time portal to portal. too bad only a few governments could afford that.

--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
--Schiller

Like most of the best, you got tough lessons like that early in your career and learned from them.

--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
--Schiller

You just made it into my file of snappy sayings :-) Should I attribute this to you Spehro?

Jeroen Belleman

Sure.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

For some 1 is the right number, for others none, for me it was 6.

--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
--Schiller

For real fun, try having to teach your mother while on the road while you are just 14.

--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
--Schiller