Big crowbar module for <4VDC?
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From: Jasen Betts on 20 Dec 2008 05:06 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.
From: Jan Panteltje on 20 Dec 2008 10:10 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 :-)
From: Jim Thompson on 20 Dec 2008 10:26 On 20 Dec 2008 10:06:18 GMT, Jasen Betts <jasen(a)xnet.co.nz> wrote: >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. Blows fuse and it leaves no charred remains like certain other suggestions must do ;-) Linear regulator can be tested for failure mechanism with no worry that crowbar destroyed evidence. ...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: Jim Thompson on 20 Dec 2008 10:31 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. ...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 | Why are Europeons so ignorant? They think they know it all about the U.S.A. But never have bothered to visit
From: Jan Panteltje on 20 Dec 2008 10:36
On a sunny day (Sat, 20 Dec 2008 08:31:28 -0700) it happened Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in <5r3qk45auhj43ftd9qrkvr9d0r4ibskg0e(a)4ax.com>: >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. Yes, you. |