Big crowbar module for <4VDC?
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From: Paul Hovnanian P.E. on 18 Dec 2008 23:25 Joerg wrote: > > Hello All, > > After modding a 5V linear to 3.3V I feel a bit iffy about the crowbar, > considering the Dollar amount that is going to be connected to it. The > original crowbar is partially under (!) a big electrolytic, a bear to > modify. Plus it probably isn't a good one to begin with, couldn't see a > TL431 in there. Why mod it? If you have access to a point within the PS circuitry, just add your own crowbar. Since the existing one is designed for 5V output, odds are that it will never operate and won't interfere with your added circuitry. > So, is there a big old fat crowbar module anywhere that can wrestle an > 18A linear supply? The usual OVP modules from Condor and others only > have a smallish TO220 SCR in there which would probably go kablouie > before it can protect anything. Put in whatever SCR it will take to work with the current available. If your load is that valuable, a few dollars more for a beefy part won't break the budget. I'm assuming this isn't for high volume production (in which case, a custom designed PS would be better). -- Paul Hovnanian mailto:Paul(a)Hovnanian.com ------------------------------------------------------------------ I had a dog that would chase anyone riding a bicycle. In the end I had to take his bicycle away.
From: Joerg on 19 Dec 2008 00:35 Paul Hovnanian P.E. wrote: > Joerg wrote: >> Hello All, >> >> After modding a 5V linear to 3.3V I feel a bit iffy about the crowbar, >> considering the Dollar amount that is going to be connected to it. The >> original crowbar is partially under (!) a big electrolytic, a bear to >> modify. Plus it probably isn't a good one to begin with, couldn't see a >> TL431 in there. > > Why mod it? If you have access to a point within the PS circuitry, just > add your own crowbar. Since the existing one is designed for 5V output, > odds are that it will never operate and won't interfere with your added > circuitry. > Well, but I want it to work. Ideally at 3.6 volts or so. >> So, is there a big old fat crowbar module anywhere that can wrestle an >> 18A linear supply? The usual OVP modules from Condor and others only >> have a smallish TO220 SCR in there which would probably go kablouie >> before it can protect anything. > > Put in whatever SCR it will take to work with the current available. If > your load is that valuable, a few dollars more for a beefy part won't > break the budget. I'm assuming this isn't for high volume production (in > which case, a custom designed PS would be better). > Guess I'll have to if nothing commercially available comes up. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Frithiof Jensen on 19 Dec 2008 05:48 "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> skrev i meddelelsen news:9oalk4pn5eri9dp209c5vqmiscb5na8ep8(a)4ax.com... > > They're probably all Democrats ;-) Communist Chinese actually ;-) .
From: Jan Panteltje on 19 Dec 2008 05:51 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.
From: krw on 19 Dec 2008 08:05
In article <494b7c18$0$56793$edfadb0f(a)dtext02.news.tele.dk>, frithiof.jensen(a)diespammerdie.jensen.tdcadsl.dk says...> > "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> skrev i > meddelelsen news:9oalk4pn5eri9dp209c5vqmiscb5na8ep8(a)4ax.com... > > > > They're probably all Democrats ;-) > > Communist Chinese actually ;-) . The difference being that Chi-Comms like business. |