- Tantalum Capacitors - 11 Updates
- EPA caught VW cheating - how does the car know it's being tested? - 14 Updates
| krw <krw@nowhere.com>: Sep 23 12:47PM -0400 >voltage drop over the resistance was negligible, but the reduction in >current spikes through the tantalums was considerable. >They didn't blow up anymore and neither did the IGBTs. The point being that by adding the resistor, you've increased the "ESR" of the cap(-resistor). You might just as well use an aluminum cap in its place if ESR doesn't matter. |
| John Devereux <john@devereux.me.uk>: Sep 23 06:35PM +0100 > The point being that by adding the resistor, you've increased the > "ESR" of the cap(-resistor). You might just as well use an aluminum > cap in its place if ESR doesn't matter. No there is still a low-ESR decoupling for the IC. I do that a lot since it isolates the IC rail from spikes on the main power rail. (Not with tants though). -- John Devereux |
| rickman <gnuarm@gmail.com>: Sep 23 02:11PM -0400 On 9/23/2015 12:47 PM, krw wrote: > The point being that by adding the resistor, you've increased the > "ESR" of the cap(-resistor). You might just as well use an aluminum > cap in its place if ESR doesn't matter. He is talking about this... Vcc ---/\/\/\---+-------+ | | IC = | | --- --- - - Not this... Vcc ----+----/\/\/\-----+ | | IC = | | --- --- - - -- Rick |
| Jeff Liebermann <jeffl@cruzio.com>: Sep 23 11:16AM -0700 >Tantalums have such a low HF resistance that it is sometimes recommended >to put a current limiting resistor in series if there is a serious ripple >voltage around. Really? <http://my.execpc.com/~endlr/esr.html> Click on the graph near the bottom of the page. Note that the low-ESR aluminum electrolytic is only slightly worse than the equivalent tantalum. If polymer caps were added to the graph, it would be about the same as tantalum. The reason we used tantalum (in marine radios) over electrolytics was that they were smaller, lasted longer, were sealed, more stable capacitance over temperature, more stable ESR over temperature, and were easier to handle in a wave solder and washing machine environment. While each benefit for tantalum is admittedly minor, the combination of all the aforementioned benefits made them quite a superior device. The only downside was the cost, which limited their use to areas where a very low ESR was needed. Your "current limiting resistor" sounds like something that would raise the ESR of the device by the resistor value. Much depends on the ripple current, which presumably in a switching power supply filter cap, is quite high. When playing with ESR's of less than 1 ohm, minor variables such as PCB plating thickness and trace width/length become significant. When the lowest ESR is at the series self resonant frequency of the capacitor, the selection of type, value, voltage, package, etc also become important. Much of the RF circuitry involved in a radio requires broadband bypassing. That rapidly becomes an exercise in capacitor selection based on series resonant frequencies and lowest overall ESR. It was not unusual to have 3 different bypass caps in parallel at key locations, such as the corners of PCB's to chassis ground points. Adding a series resistor to the tantalum cap would not have worked for obtaining the lowest possible ESR. >a large HF ripple due to the switching of the IGBT's that it blew the >tantalums out of the control board, after which the IGBT's also went to >pieces. Did the ripple voltage on the power supply line increase with the added series resistance? -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
| Jeff Liebermann <jeffl@cruzio.com>: Sep 23 11:58AM -0700 On Tue, 22 Sep 2015 19:02:33 -0700, John Larkin >The tantalum thing is very erratic. Some batches blow up, some are >fine. I guess I should mention that Intech had two divisions. I worked for the marine radio division. There was also a "modular products" division that made military grade modules (A/D, D/A, amps, etc). Both divisions shared many of the same components including a wide selection of tantalum caps. Most of the modules ran on +15/-15 VDC and used 35 VDC rated tantalums. As I vaguely recall, there were no aluminum caps used in anything that had to work from -40C to +105C. If tantalums were that failure prone, they would never have survived in a mil spec environment. Some typical radio boards. This is Intech M3600 2-30 MHz 150 watt PEP synthesized SSB radio circa 1977(?): <http://www.hellocq.net/forum/read.php?tid=226493> The boards are a mix of purple potted electrolytics and blue or orange colored tantalums. No failures in 10 years of similar radios. There also seems to be an aging mechanism involved. I'm the not so proud owner of several Wavetek 3000B service monitors: <http://802.11junk.com/jeffl/pics/home/slides/BL-shop5.html> Some of the tantalums have shorted over the years. I'm replacing them as I blunder forward. No fires, smoke, or discoloration in about 10 years of fixing these. I also have some other equipment with similar tantalum problems. I recently repaired an M3600 radio which showed no evidence of deteriorating or failed tantalums. Has something changed in the last 40 years in how tantalums are made? >voltages, with no overshoot spikes. It's dV/dT, namely peak current, >that can ignite tiny particles of tantalum, which then burn in the >solid MnO2 electrolyte. I think you mean dI/dT which provides the heating necessary to ignite the tantalum. That all sounds logical, but doesn't explain why a similar amount of heating caused by normal ripple current doesn't set fire to the capacitor. I've seen some heat darkened tantalums operating normally without ignition. Like the bulging electrolytics and burning LiIon batteries, I suspect there's been some changes in production methods (like skipping important steps to save pennies). >carefully. >https://dl.dropboxusercontent.com/u/53724080/Parts/Caps/Bang.jpg >https://dl.dropboxusercontent.com/u/53724080/Parts/Caps/Fried_Tant_1.JPG Nice photos. Having done post mortem failure analysis a few times, I like to look at the damage and try to guess what was the cause. It's fairly easy to inspect the remains and estimate the violence of the failure. For tantalum, there's usually something left of the wire leads or carbonized slug. It gets hot, belches flames, carbonizes, falls apart, which finally breaks the connection. However, the OP mentioned that: "The first thing I notice when looking inside is that the small SMT 100uF 10V tantalum capacitor C109 has completely vacated - it appears to be gone, blown right off the board. There are some little fragments rattling around in the case." That's not what I consider to be a conventional tantalum burn failure. The cap should have looked like the one in the above photos. Something caused this one to explode rather than burn, which is why I suggested that a much higher voltage wall wart was involved. I don't think the tantalum was at fault simply because it was the first thing to blow and was the most obvious physical failure. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
| Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Sep 23 03:19PM -0400 On 09/23/2015 01:35 PM, John Devereux wrote: > No there is still a low-ESR decoupling for the IC. I do that a lot since > it isolates the IC rail from spikes on the main power rail. (Not with > tants though). An aluminum electro in parallel with a smaller ceramic makes a nice lead-lag network for the voltage regulator, if you do it right. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net |
| John Larkin <jjlarkin@highlandtechnology.com>: Sep 23 12:37PM -0700 On Wed, 23 Sep 2015 15:19:56 -0400, Phil Hobbs >lead-lag network for the voltage regulator, if you do it right. >Cheers >Phil Hobbs One thing that doesn't show up on the power supply schematic sheet is the zillions of chip bypass caps on other sheets. One might have tens of uF of paralleled super-low ESR ceramic caps on a big power pour. A tantalum seems to have the right ESR to damp the whole mess, even when a regulator should be unstable with just the ceramics. One test for stability is to apply a pulse load and see how the regulator reacts. I saw one big board (part of an Anritsu DRAM tester system) that had 3000 bypass caps. It's not unusual to see an FPGA appnote that recommends a hundred caps or so per chip. |
| Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Sep 23 04:15PM -0400 On 09/23/2015 10:24 AM, John Larkin wrote: >> Use another tantalum. Solid are best, but hard to find. > Most tantalum caps are solids, with the MnO2 electrolyte. Less common > are liquid types and polymers. Wet tants are super-expensive. ISTR they're basically military-only. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net |
| John Larkin <jjlarkin@highlandtechnology.com>: Sep 23 01:28PM -0700 On Wed, 23 Sep 2015 16:15:59 -0400, Phil Hobbs >Wet tants are super-expensive. ISTR they're basically military-only. >Cheers >Phil Hobbs Pretty much. We used to use them in mil systems. The cases were silver, back when silver wasn't too expensive. The electrolyte is acid, which eventually eats its way out. I think the cases may be tantalum now. CSR13 part numbers, something like that. A few bucks each, about the price of a low-end steak dinner then. |
| piglet <erichpwagner@hotmail.com>: Sep 23 09:34PM +0100 On 23/09/2015 15:24, John Larkin wrote: > Most tantalum caps are solids, with the MnO2 electrolyte. Less common > are liquid types and polymers. There is even solid aluminum, now only made by Vishay (I think) and cost more than equivalent tantalum. The ones I use are resin dipped through hole parts and look like a big resin dipped tantalum bead. Nice caps, very low ESR and supposedly very reliable, claim "no-known wear-out mechanism". piglet |
| John Larkin <jjlarkin@highlandtechnology.com>: Sep 23 01:56PM -0700 On Wed, 23 Sep 2015 21:34:38 +0100, piglet <erichpwagner@hotmail.com> wrote: >very low ESR and supposedly very reliable, claim "no-known wear-out >mechanism". >piglet Do you mean polymer aluminums? Those are great, super low ESR. We use United Chem-Com and Nichicon. 47 cents for 180 uF 6.3 volts, about 2x tha price of a regular aluminum cap. |
| Winston_Smith <invalid@butterfly.net>: Sep 23 06:42PM On Wed, 23 Sep 2015 10:00:58 -0400, Steve W. wrote: > I would bet there will be a software "patch" that will > erase the different testing maps, the cars will then meet the original > EPA standards I think the point is that the cars can only either meet the emissions standards with reduced drivability, or, with the addition of a urea system. Either will be expensive. |
| Winston_Smith <invalid@butterfly.net>: Sep 23 06:43PM On Wed, 23 Sep 2015 08:15:24 -0700, trader_4 wrote: > a whole lot of people who are already cutting corners, > going to the edge of what's legal or beyond, will just go > further. Someone somewhere said it's not the severity of the punishment that deters crime, but the certainty of it. |
| Winston_Smith <invalid@butterfly.net>: Sep 23 06:45PM On Tue, 22 Sep 2015 21:26:40 -0700, Bob F wrote: > Update 9/22: This morning VW announced that the cheating issue on diesel engines > is much more vast than initially expected. The company admitted to cheating on > 11 million diesel engines worldwide. And the CEO stepped down today. VW even, apparently, fingered a few employees to the German justice system (which I'd love to know more about - because it gets down to "WHO" did it). |
| Winston_Smith <invalid@butterfly.net>: Sep 23 06:48PM On Tue, 22 Sep 2015 22:22:32 -0500, Vic Smith wrote: > That was tongue and cheek. But a congressional committee can > investigate a ham sandwich if they please. Thanks for explaining. I just wonder why many people think EVERYTHING is caused by one party or the other. In this case, VW simply cheated. They broke laws on purpose. And they repeatedly lied (probably to avoid detection). All to make money. At the expense of everyone else. If I was a competitor, I'd be livid that I had to spend money to meet a standard that VW didn't even bother to meet, and yet profited for years by not meeting. |
| Winston_Smith <invalid@butterfly.net>: Sep 23 06:48PM On Tue, 22 Sep 2015 23:08:40 -0400, Ed Pawlowski wrote: > engineers. Someone had to come up with the idea, design, build, test, > and approve everything. The guys on the line installing would probably > have no idea, just another part. Higher level in engineering would know. I don't know how VW works, but, in one newspaper, they "speculated" that this kind of cheat had to be approved at the top level. |
| Winston_Smith <invalid@butterfly.net>: Sep 23 06:50PM On Wed, 23 Sep 2015 10:23:43 -0400, Steve W. wrote: > The actual program change is easy. It could be hidden just about > anywhere but is likely very simple. But don't you think the code, which clearly had legal implications known to all involved, would have to be signed off at the highest level? |
| Winston_Smith <invalid@butterfly.net>: Sep 23 06:51PM On Wed, 23 Sep 2015 07:03:25 -0500, Dean Hoffman wrote: > They shouldn't be parking in the special parking spaces for > low emission vehicles. That's an interesting observation! |
| jurb6006@gmail.com: Sep 23 11:55AM -0700 >"but under the DMCA it would be illegal for vehicle owners OR >the EPA to attempt reverse-engineering it from the object load." Not so sure about that. There is probably an exemption for law enforcement purposes. Plus the fact it is really not worth copyrighting. It's not like Microsoft Office or anything, all it does is engine control. |
| "Steve W." <csr684@NOTyahoo.com>: Sep 23 03:15PM -0400 Winston_Smith wrote: > standards with reduced drivability, or, with the addition of a urea > system. > Either will be expensive. The cars can meet the standards as built. The only real change would be that the mpg numbers will fall to the original EPA numbers. The only other thing will be an increase in the amount of times the systems burn the residuals in the trap. -- Steve W. |
| John Robertson <spam@flippers.com>: Sep 23 12:27PM -0700 On 09/23/2015 11:48 AM, Winston_Smith wrote: > If I was a competitor, I'd be livid that I had to spend money to meet > a standard that VW didn't even bother to meet, and yet profited for > years by not meeting. That's assuming none of the other auto makers pull(ed) the same trick. I think this is the tip of an iceberg... John :-#)# -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
| Ed Pawlowski <esp@snet.net>: Sep 23 04:09PM -0400 On 9/23/2015 10:00 AM, Steve W. wrote: > Bob F wrote: > VW might just decide to leave the market in the US. Doubt they will walk away from a huge market where they have been well established. |
| "." <.@dot.com>: Sep 23 03:22PM -0500 On 9/23/2015 9:00 AM, Steve W. wrote: > longer legal for road use in the US, registrations and insurance would > be revoked. > VW might just decide to leave the market in the US. It has been reported that less than one in twenty-two problem cars were actually sold in the U.S. |
| NoSpamForMe <NoSpamForMe@g.mail>: Sep 23 04:43PM -0400 Virtually all marketing material is a lie. Did you really think that shopvac you bought at McLowesDepotBigBoxSuperMart has a 6HP motor on it? Did you really think that $49 TV antenna can pull in stations from 200 miles away? Did you really think your new car would actually get the mpg advertised on the sticker? You really think your extended warranty will cover everything? Did you really think Dick Network would deliver all those channels for $19.95 / mo? So what if VW stretches the truth a bit, they ***all*** do. Do you know how to tell if a car salesperson is lying? Their lips are moving. |
| "Robert Green" <robert_green1963@yah00.com>: Sep 23 04:29PM -0400 "Winston_Smith" <invalid@butterfly.net> wrote in message news:mturtd$bbh$4@news.mixmin.net... > > further. > Someone somewhere said it's not the severity of the punishment > that deters crime, but the certainty of it. My crim. prof didn't believe much in deterrence and pointed out that in Merry Olde England "Pickpockets picked pockets at the hangings of pickpockets." People were so entranced by watching someone *else* dying that they became excellent targets for pickpockets. It's also been shown that it's very hard to deter crimes of passion because people are often way out of their minds when they kill lovers, spouses, children, etc. -- Bobby G. |
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