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Re: (OT) Storage (8*IDE HDs) any experiences? - diodes

hi ya...

though we are getting slightly off topic...
	- dual power supply issues...

the problem is how to connect two power supplies together...
one at 5.25v  and the other at extreme of 4.75v

if using just a diode...( no matter what kind - power or schottky )... it
wont work as one diode will have a bigger voltage drop across it than its
normal .1v or .7v or whatever it might be...

voltage drop is NOT the issue.... you need something that will
allow a range of Vce  or Vsd  that will pass the normal current
and also support the surge current when you first turn on the
powersupply to spin the drives...

and since diodes/resistors are not active devices...
you will incurr significant loss of regulation and huge current
spikes.... ( good way to get a disk go *poof* on ya )

dual power supply is tricky biz...guess thats why its $500 for a pair...
or more or less... not the atx/pc stuff for $25 each

have fun

On Thu, 3 May 2001, Stephan Hachinger wrote:

> > Hi!
> >
> >
> > > > at these extremes... the diodes wont help....and the dioes will simply
> > > > burn up due to the current it has to pass to get to that "voltage"
> > > > one side being a diode drop ( 0.7v ) across itself..
> > > > - a power mosfet is better suited ...
> >
> > hmm, mosfet doesn't make sense to me - IIRC they only work like switches
> >
> > I think you should use "Shotkey-diods" the largest one i know could pass
> > 200 ampere - and they've less than ~0.4V voltage drop
> Hi!
> Mosfets are a kind of transistors with less loss of energy than a bipoar
> type. I agree that the only thing you could use is a shottky diode, the drop
> is about 0.1-0.2 Volts, I think; therefore it won't produce so much heat and
> maybe you won't even need any heatsinks for them. But I think it is
> generally not a good thing to reduce the supply voltage by 0.2 Volts this
> way, because computers are very sensitive to voltage changes... If there
> will be a high load for only a short time, the voltage maybe drops down the
> specs and your components are down.
> Regards,
> Stephan Hachinger
> -- 
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