---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 05/24/12: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:01 AM - Schottky steering diodes in parallel (user9253) 2. 09:27 AM - Re: Schottky steering diodes in parallel (Richard Tasker) 3. 10:23 AM - Re: Schottky steering diodes in parallel (user9253) 4. 11:55 AM - On a brighter note: (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 06:01:56 AM PST US Subject: AeroElectric-List: Schottky steering diodes in parallel From: "user9253" A search of the archives turned up this: > 01/02/06 > http://www.opensubscriber.com/message/aeroelectric-list-digest@matronics.com/2983404.html > . . . . .You can wire multiple diodes in parallel but don't depend > on this technique to "double" current rating of the steering diode. > Bob . . . Does the above statement apply only to multiple diodes contained in one package such as a bridge rectifier? If two discrete diodes are connected in parallel, would the total current capacity be almost doubled? If not, then why? It seems to me that each diode would carry half of the total current. If one of the diodes were to carry more than half of the current, then the voltage drop across that diode would increase. Thus the load would then draw current from the other diode which has a higher voltage output. Your explanation of diode physics will be appreciated. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=373751#373751 ________________________________ Message 2 _____________________________________ Time: 09:27:13 AM PST US From: Richard Tasker Subject: Re: AeroElectric-List: Schottky steering diodes in parallel If the electrical characteristics of the two diodes were exactly the same, then your supposition would be correct. The problem comes in when they are not exactly the same - which is all the time. For example, one diode may have a 0.65V drop at one amp while the other diode only has to pass 1/2 amp for the same voltage drop. So in this example, with a total current of 1.5A, one diode handles 2/3 of the total current and the other handles 1/3. Because the voltage drop changes very little for a change in current, it only takes a very small difference in characteristics to cause a big mismatch in current sharing. Dick Tasker user9253 wrote: > --> AeroElectric-List message posted by: "user9253" > > A search of the archives turned up this: > >> 01/02/06 >> http://www.opensubscriber.com/message/aeroelectric-list-digest@matronics.com/2983404.html >> . . . . .You can wire multiple diodes in parallel but don't depend >> on this technique to "double" current rating of the steering diode. >> Bob . . . > Does the above statement apply only to multiple diodes contained in one package such as a bridge rectifier? > If two discrete diodes are connected in parallel, would the total current capacity be almost doubled? If not, then why? It seems to me that each diode would carry half of the total current. If one of the diodes were to carry more than half of the current, then the voltage drop across that diode would increase. Thus the load would then draw current from the other diode which has a higher voltage output. > Your explanation of diode physics will be appreciated. > Joe > > -------- > Joe Gores > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=373751#373751 > > ________________________________ Message 3 _____________________________________ Time: 10:23:30 AM PST US Subject: AeroElectric-List: Re: Schottky steering diodes in parallel From: "user9253" Thanks Dick Tasker, You explained that very well. It looks like it would be better to use one diode rated for the current, rather than parallel smaller diodes. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=373776#373776 ________________________________ Message 4 _____________________________________ Time: 11:55:31 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: On a brighter note: Tried to post this last night but I was not cognizant of changes Matt had to make to the SMTP servers at matronics. Seems some Brazilian hacker figured out a way to pipe gigabytes of trash through Matt's machines. He got it fixed but it took me awhile to become aware of the changes to my email client needed to make me compatible. So . . . onward and upward . . . -------------------------- I sure hope that this list isn't going to go down a path that leads to this kind of end. I don't think that we're anywhere close to that state yet, and that's why I bring it up- this is how it starts, and like many other infectious patterns, early intervention is certainly the most effort-effective solution. I was about to suggest the same thing Jared, thanks. I know it's getting hot and the hammock out under the tree looks inviting . . . but let's not let the heat stagnate our gray matter or civlity. Which reminds me. I have a list server set up for a forum on perceptions of the human condition. I've got about 50 names of individuals who indicated and interest. All I need is a 36 hour day . . . But I do know that I have enough faith in Bob's work to bet my life on it, and I'd certainly like to have a place where I can stay abreast of changes and updates to the system designs, and the gradual changes to what we think of as best practices. Fortunately, very few cases of serious injury or damage has roots in system architecture or selection of components. I think the greatest value of what we offer here is collaboration on failure tolerant design and lowest cost of ownership tailored to the aircraft and its proposed mission. Wouldn't it be great if this list can continue to be that source? Isn't that more likely to be the case if we can stay away from these kinds of discussions, whether or not we agree with the points? Agreed. On a brighter note, the power FETS for the joint collaboration on a new Wig-Wag are here. I thought I was going to get time to build some POC first articles last night . . . but one of the light fixtures over my bench crapped. TWO lessons learned: These $10 Wallmart fixtures are very unfriendly for replacement of ballast. Further, if ballast replacement in less than 10 years is a modern reality, then make sure your installation is friendly to the task of taking the entire fixture down for replacement. The toggle bolts I used to hold a two-fixture strip to the ceiling went through close fit holes in the fixture (insert cursing and blood spatters here). NOW the bolt goes through a large clearance hole courtesy of Mr. Dremmel and his magic cut-off wheels. The next replacement will be easy. Anyhow, I'll get the two POC items built this evening. Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.