Big crowbar module for <4VDC?
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From: Jim Thompson on 20 Dec 2008 12:49 On Sat, 20 Dec 2008 16:36:49 +0000, John Devereux <john(a)devereux.me.uk> wrote: >Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> writes: > >> On Sat, 20 Dec 2008 15:49:59 +0000, John Devereux >> <john(a)devereux.me.uk> wrote: >> >>>Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> writes: >>> > >[...] > >>>> Jerk, Learn to read. AND: I DIDN'T post any diagram. AND: It DOES >>>> PROTECT the load... some people here are just TOO STUPID to understand >>>> simple solutions. >>> >>>I suppose it would not protect the load against externally- or load- >>>generated overvoltages. >> >> The "load" generated its own over-voltage ?:-) > >Sure, I was thinking of something like a motor controller, or perhaps >JL's NMR machine. On a typical "linear regulator". Gimme a break ;-) > >> This thread started as protecting the load from failure of a simple >> 3.3V linear regulator. >> >> Exotic systems would require case-by-case analysis... for example... >> >> After the Challenger disaster a complete system-by-system, >> component-by-component analysis was ordered to determine any possible >> fault mechanisms. >> >> It was yours truly (consulting at Sperry Space, later Honeywell Space) >> who found the power supply redundancy fault... one supply down, they >> all go down. >> >> It needed a fix that _wasn't_ a complete redesign (requiring all kinds >> of compliance/qualification testing). >> >> So I came up with a fix using HexFETs... all we had to qualify was the >> HexFET itself (they had no prior "S" rating). >> >> So I have the honor of getting the first HexFET into space ;-) > >Sounds like the "oring controllers" some of the semi manufacturers >seem to be peddling. > >> Simple crow-barring of a power supply output, without any well-defined >> relief/release mechanism seems down-right stupid to me. Citing that >> everyone is doing it doesn't make it good... it only means it's >> "cheap" ;-) > >No argument here. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine Sometimes I even put it in the food
From: John Devereux on 20 Dec 2008 13:32 Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> writes: > On Sat, 20 Dec 2008 16:36:49 +0000, John Devereux > <john(a)devereux.me.uk> wrote: > >>Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> writes: >> >>> On Sat, 20 Dec 2008 15:49:59 +0000, John Devereux >>> <john(a)devereux.me.uk> wrote: [...] >>>> >>>>I suppose it would not protect the load against externally- or load- >>>>generated overvoltages. >>> >>> The "load" generated its own over-voltage ?:-) >> >>Sure, I was thinking of something like a motor controller, or perhaps >>JL's NMR machine. > > On a typical "linear regulator". Gimme a break ;-) Well I confess I can't remember what the OP's application was now; it seems so long ago :) .....(goes up thread)... Aha, it's Joergs big old linear supply he found. Well who knows what he's controlling - ISTR he wanted very low noise, and specifically linear. Sounds fairly exotic to me. [...] -- John Devereux
From: Michael A. Terrell on 20 Dec 2008 13:59 Jim Thompson wrote: > > On Sat, 20 Dec 2008 15:49:59 +0000, John Devereux > <john(a)devereux.me.uk> wrote: > > >Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> writes: > > > >> On Sat, 20 Dec 2008 15:10:11 GMT, Jan Panteltje > >> <pNaonStpealmtje(a)yahoo.com> wrote: > >> > >>>On a sunny day (20 Dec 2008 10:06:18 GMT) it happened Jasen Betts > >>><jasen(a)xnet.co.nz> wrote in <giig2q$kmd$7(a)reversiblemaps.ath.cx>: > >>> > >>>>On 2008-12-19, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: > >>>>> On a sunny day (Thu, 18 Dec 2008 18:32:11 -0800) it happened Joerg > >>>>><notthisjoergsch(a)removethispacbell.net> wrote in > >>>>><TID2l.10279$yr3.2278(a)nlpi068.nbdc.sbc.com>: > >>>>> > >>>>>>> http://www.hobbyprojects.com/thyristor_triac_and_diac/thyristor_as_a_crowbar.html > >>>>>>> > >>>>>> > >>>>>>Has the author ever heard of a gate trigger voltage? Assume 1.5V for > >>>>>>now: Zener 5.1V plus Vgt = 6.6V. Phssst ... crackle ... pop ... *BANG* > >>>>>>... there goes the majority of connected logic chips. Many of those > >>>>>>won't take anything above 6V. > >>>>>> > >>>>>>The proper way to do a crowbar is with a TL431. > >>>>> > >>>>> Crowbars are to protect the LOAD, not the supply, and should be at the OUTPUT. > >>>>> In case of a 100K$ load and a 100$ supply, the choice is easy. > >>>>> Shorting before the regulator does not guarantee energy in any caps and > >>>>> or inductors in the circuit does not make it to the load. > >>>>> Simple. > >>>> > >>>>You can put the crowbar SCR across the input to the regulator and the > >>>>over-voltage detector across the output - a kind of feedback. > >>>>I suspect that is how Jim designs his. > >>> > >>>Yes you can do that, and he even showed a small kid diagram with a 7805 IIRC. > >>>But that will _not_ protect what happens on the supply line. > >>>Jimmy has the typical rightist republican thinking: > >>> His method protects his own design, not the load :-) > >> > >> Jerk, Learn to read. AND: I DIDN'T post any diagram. AND: It DOES > >> PROTECT the load... some people here are just TOO STUPID to understand > >> simple solutions. > > > >I suppose it would not protect the load against externally- or load- > >generated overvoltages. > > The "load" generated its own over-voltage ?:-) > > This thread started as protecting the load from failure of a simple > 3.3V linear regulator. > > Exotic systems would require case-by-case analysis... for example... > > After the Challenger disaster a complete system-by-system, > component-by-component analysis was ordered to determine any possible > fault mechanisms. > > It was yours truly (consulting at Sperry Space, later Honeywell Space) > who found the power supply redundancy fault... one supply down, they > all go down. > > It needed a fix that _wasn't_ a complete redesign (requiring all kinds > of compliance/qualification testing). > > So I came up with a fix using HexFETs... all we had to qualify was the > HexFET itself (they had no prior "S" rating). > > So I have the honor of getting the first HexFET into space ;-) I would rather you had put the first donkey into orbit. -- http://improve-usenet.org/index.html aioe.org, Goggle Groups, and Web TV users must request to be white listed, or I will not see your messages. If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm There are two kinds of people on this earth: The crazy, and the insane. The first sign of insanity is denying that you're crazy.
From: Jim Thompson on 20 Dec 2008 14:06 On Sat, 20 Dec 2008 13:59:58 -0500, "Michael A. Terrell" <mike.terrell(a)earthlink.net> wrote: > >Jim Thompson wrote: >> >> On Sat, 20 Dec 2008 15:49:59 +0000, John Devereux >> <john(a)devereux.me.uk> wrote: >> >> >Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> writes: >> > >> >> On Sat, 20 Dec 2008 15:10:11 GMT, Jan Panteltje >> >> <pNaonStpealmtje(a)yahoo.com> wrote: >> >> >> >>>On a sunny day (20 Dec 2008 10:06:18 GMT) it happened Jasen Betts >> >>><jasen(a)xnet.co.nz> wrote in <giig2q$kmd$7(a)reversiblemaps.ath.cx>: >> >>> >> >>>>On 2008-12-19, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: >> >>>>> On a sunny day (Thu, 18 Dec 2008 18:32:11 -0800) it happened Joerg >> >>>>><notthisjoergsch(a)removethispacbell.net> wrote in >> >>>>><TID2l.10279$yr3.2278(a)nlpi068.nbdc.sbc.com>: >> >>>>> >> >>>>>>> http://www.hobbyprojects.com/thyristor_triac_and_diac/thyristor_as_a_crowbar.html >> >>>>>>> >> >>>>>> >> >>>>>>Has the author ever heard of a gate trigger voltage? Assume 1.5V for >> >>>>>>now: Zener 5.1V plus Vgt = 6.6V. Phssst ... crackle ... pop ... *BANG* >> >>>>>>... there goes the majority of connected logic chips. Many of those >> >>>>>>won't take anything above 6V. >> >>>>>> >> >>>>>>The proper way to do a crowbar is with a TL431. >> >>>>> >> >>>>> Crowbars are to protect the LOAD, not the supply, and should be at the OUTPUT. >> >>>>> In case of a 100K$ load and a 100$ supply, the choice is easy. >> >>>>> Shorting before the regulator does not guarantee energy in any caps and >> >>>>> or inductors in the circuit does not make it to the load. >> >>>>> Simple. >> >>>> >> >>>>You can put the crowbar SCR across the input to the regulator and the >> >>>>over-voltage detector across the output - a kind of feedback. >> >>>>I suspect that is how Jim designs his. >> >>> >> >>>Yes you can do that, and he even showed a small kid diagram with a 7805 IIRC. >> >>>But that will _not_ protect what happens on the supply line. >> >>>Jimmy has the typical rightist republican thinking: >> >>> His method protects his own design, not the load :-) >> >> >> >> Jerk, Learn to read. AND: I DIDN'T post any diagram. AND: It DOES >> >> PROTECT the load... some people here are just TOO STUPID to understand >> >> simple solutions. >> > >> >I suppose it would not protect the load against externally- or load- >> >generated overvoltages. >> >> The "load" generated its own over-voltage ?:-) >> >> This thread started as protecting the load from failure of a simple >> 3.3V linear regulator. >> >> Exotic systems would require case-by-case analysis... for example... >> >> After the Challenger disaster a complete system-by-system, >> component-by-component analysis was ordered to determine any possible >> fault mechanisms. >> >> It was yours truly (consulting at Sperry Space, later Honeywell Space) >> who found the power supply redundancy fault... one supply down, they >> all go down. >> >> It needed a fix that _wasn't_ a complete redesign (requiring all kinds >> of compliance/qualification testing). >> >> So I came up with a fix using HexFETs... all we had to qualify was the >> HexFET itself (they had no prior "S" rating). >> >> So I have the honor of getting the first HexFET into space ;-) > > > I would rather you had put the first donkey into orbit. I tried, but the donkey turned to donkey doo during the acceleration ;-) ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine Sometimes I even put it in the food
From: Michael A. Terrell on 20 Dec 2008 14:12
Jim Thompson wrote: > > Michael A. Terrell wrote: > > > > I would rather you had put the first donkey into orbit. > > I tried, but the donkey turned to donkey doo during the acceleration > ;-) We have another donkey. Care to repeat the tests? -- http://improve-usenet.org/index.html aioe.org, Goggle Groups, and Web TV users must request to be white listed, or I will not see your messages. If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm There are two kinds of people on this earth: The crazy, and the insane. The first sign of insanity is denying that you're crazy. |