Re: (OT) Storage (8*IDE HDs) any experiences? - diodes
On Wed, May 02, 2001 at 04:49:27PM -0700, Alvin Oga wrote: the diodes need to be power diodes... vs signal diodes given you cannot tie the power supplies at two diff voltages together... you have to isolate it somehow... ( the power diode method ) I'm a bit hazy on how this actually works, but I would guess that each supply's output goes through a diode (forward biased) and the lower potential sides of the diodes would be connected. Thus not much current flows back the other way. but more importantly, its primary purpose is to allow for the two power supply at different voltages ( +5.25v and +4.75v ) to be tied together at these extremes... the diodes wont helpand 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 ... You will need some large diodes and you may well need cooling ie heatsinks. Hamish -- Hamish Moffatt VK3SB [EMAIL PROTECTED] [EMAIL PROTECTED]
Re: (OT) Storage (8*IDE HDs) any experiences? - diodes
Hi! at these extremes... the diodes wont helpand 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 :wq - until next mail B-), l8r Peter -- :~~ [EMAIL PROTECTED] ~~: : student of technical computer science : : university of applied sciences krefeld (germany) : ~~ FD314F21 C7 AE 2F 28 C1 33 71 77 0D 77 CD 6E 58 E9 06 6B
Re: (OT) Storage (8*IDE HDs) any experiences? - diodes
At Thu, 3 May 2001 22:36:27 +0200 , Peter Bartosch [EMAIL PROTECTED] wrote: hmm, mosfet doesn't make sense to me - IIRC they only work like switches A MOSFET is a type of field-effect transistor ... hence the FET part of the name -- it can be sued for much more than a switch. Get your own FREE E-mail address at http://www.linuxfreemail.com Linux FREE Mail is 100% FREE, 100% Linux, and 100% yours!
Re: (OT) Storage (8*IDE HDs) any experiences? - diodes
Hi! at these extremes... the diodes wont helpand 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
Re: (OT) Storage (8*IDE HDs) any experiences? - diodes
http://www.dell.com/us/en/bsd/products/model_pedge_1_pedge_2550.htm ...Has a system with dual power supplies. If anyone is interested in putting together a system like that, I suggest they go ahead and buy one. Otherwise, let's leave the design stuff to the power supply engineers at Power One and the other big power supply companies. They've got loads of (trained) people to take care of the design debates (including the use of Schottky Diodes). If further discussion on this toppic is desired, perhaps news:alt.engineering.electrical would be a more appropriate forum (or any of a number of other resources that show up in a google search). The debate was off-topic to begin with, strayed even further, yet stayed interesting with the concerns over load-ballancing supplies. Debating design features of power supplies is really wandering off of the beaten path... especially given the lack of experience most of us (the members of debian-user) have with the subject. Sorry for adding to the noise, but geez, this list is chatty enough already to be almost unmanagable. Bottom line: let's let the discussion die or else move it over to another list or NG. --Rich (loads of chatter deleted) -- _ Rich Puhek ETN Systems Inc. _
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 alvin On Thu, 3 May 2001, Stephan Hachinger wrote: Hi! at these extremes... the diodes wont helpand 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 -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: (OT) Storage (8*IDE HDs) any experiences? - diodes
hi ya I think if you use a diode to connect the outputs you are limiting the current flow in one way only. And why would you want to do this? the diodes need to be power diodes... vs signal diodes given you cannot tie the power supplies at two diff voltages together... you have to isolate it somehow... ( the power diode method ) - even putting two batteries in parallel dont work... - - and it gets real fun when you put car batteries in parallel - and if you can get it working... it makes for a very good UPS - - one car battery lasts about 15hrs ...for a P3-500 class server - sitting idle with no AC power yes...it might limit the current... and a resistor is bad too cause they both nullifies/weaken the accurate voltage regulation.. - ie. big current spikes will occur but more importantly, its primary purpose is to allow for the two power supply at different voltages ( +5.25v and +4.75v ) to be tied together at these extremes... the diodes wont helpand 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 ... think we're going off course...but... thats the fun of watching things blow up in the lab when ne does whacky things like connect two power supplies together??? ( smoke test or heat test ) c ya alvin http://www.Linux-1U.net ...
