Ping John Larkin: Question on MAX
in [Design]
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From: John Larkin on 1 Jun 2010 18:42 On Tue, 1 Jun 2010 15:24:09 -0700, "Joel Koltner" <zapwireDASHgroups(a)yahoo.com> wrote: >"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message >news:101b06hlvadd656tnr2o6f073fpf81tjnu(a)4ax.com... >> We have a document that tells how to assign stock numbers to parts. >> Resistors and caps wind up being in value order. >> >> In part number 104-1600, the 104 specifies an 0805 ceramic cap; 160 >> specifies 100 pF, per an algorithm. The last digit allows us to have >> up to 10 different 0805 100pF parts. We currently have two, 1% and >> 10%. > >Ah, interesting. ...although I might be tempted to have an algorithm spit out >something more like XYYY where the component value is then 0.YYY * 10^X or >something (so 113k->6113, 1.12k->4112, etc. -- this still sorts correctly), >but I expect you guys kicked around such an idea and decided your way was >preferable. Neat... We needed that last digit as a sequence number for parts with the same value but different tolerances or tc's or whatever. And we liked the idea of a 7-digit "telephone number" as being easy to use. John
From: krw on 1 Jun 2010 18:43 On Tue, 01 Jun 2010 11:05:26 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Joel Koltner wrote: >> "Joerg" <invalid(a)invalid.invalid> wrote in message >> news:86kn17FktaU1(a)mid.individual.net... >>> Yeah, but when an employee quits that's usually like a divorce. He or >>> she is gone. >> >> I've seen it both ways... I guess it comes down to both what the >> engineer and the company expect, and this is often the kind of thing >> that isn't ever written or formally verbalized: Some companies seem to >> take an engineer quitting as a form of betrayal and will start >> bad-mouthing his work and not want any contact and effectively blacklist >> him from being hired again, whereas other companies figure that if an >> engineer wants to check out whether or not the grass is greener >> elsewhere, if he does so during a lull between projects so that there >> isn't any huge disruption and stresses that he's happy to have people >> call him to ask for support on some old project he did, there's no need >> for bad feelings and the perhaps the guy will be invited to come back if >> the new place doesn't work out. >> >> The later might happen more in non-technical businesses, perhaps? -- My >> wife still does a few little side-projects for several of the places >> that she's previously worked for. >> > >That's the way to go, she probably has good communication skills. > >And I am not saying that consultants are always the cat's meouw just >because I am one. Once as a manager I did have to fire a consultant, for >lack of communications skills. He began fingerpointing and all that, >made my engineers unhappy and that just wasn't going to continue. >Strange thing is, years before that he used to be an excellent communicator. Things turned for the worse and he showed his true colors? When things are going well it's easy to be happy.
From: krw on 1 Jun 2010 18:54 On Mon, 31 May 2010 21:28:25 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Mon, 31 May 2010 20:48:14 -0700, "Joel Koltner" ><zapwireDASHgroups(a)yahoo.com> wrote: > >><krw(a)att.bizzzzzzzzzzzz> wrote in message >>news:0su806dlahcpgu29adn6d4i9c44j8tgid1(a)4ax.com... >>> We just skip nF completely. The only question is whether it's .001 (uF >>> assumed), or 1000pF. I guess even that ends up dependent on where it's >>> used. >>> Decoupling it's .001 and in a filter it's 1000pF. Yes, a mess. >> >>This is an area where I think those newly minted graduates do bring something >>of value to older engineers -- they don't shun nF. :-) >> >>We don't have any particularly hard and fast rules, but in general all >>capacitors and inductors get their full units spelled out (22nH, 100pF, etc.), >>whereas resistors don't have "ohms" added *unless they're 1-999 ohms* and >>hence would otherwise have no suffix at all. This is a sort of compromise >>between "ohms" spelled out looking a little dorky since ORCAD won't let you >>use a proper Omega symbol but still wanting at least something to suggest you >>didn't just forget a "k" or "M". > >We have standardized on pF, nF, uF, and, sadly, mF. Numbers are never >below 1, except 0.5 pF maybe, and never start with a decimal point. Since .1uF is the most common cap, I like to just have '.1' in the value field, rather than '100nF'. Other than that, I'd probably agree. Exceptions are dirty, so we stick to 'F' (we do use a supercap), '', and 'pF'. >Resistors are 12R, 3.01K, 22M, 3G, 1T. I suppose I'd parse 14mR or >just 14m as 14 milliohms. "12" will parse as 12 ohms. We will NEVER >use the juvenile 4k7 thing. I'll enforce that in my will. I agree. Too Europeon. ;-) >Hmmm, maybe I should parse 2.2F properly, in case we buy some >supercaps some day; I'm not doing that now. One more line of code. If you need them, be careful. Some aren't very reliable. I'm trying to get rid of the one we're using. >>I am guilty of doing dumb things like having just labeled a bunch of inductor >>in nH and then proceeding to label a bypass cap as 100nH rather than 100nF. >>Oops... > >We are all shocked, shocked. > >It is fun when you ECO replace a resistor, like R99, on a board with a >capacitor, which has to still be R99. I wonder what my crosschecker >would do in that case. Took me a minute to figure out what you were getting at... Yes, we've run into that too, though it's the first thing to go away at the next board spin. Another thing we've had to resort to a few times is stacked components. A cap on top of a feedback resistor becomes R99T, in the BOM. I don't think any of those have escaped into the wild, though. >>When we first started implementing our new MRP system some years ago now I >>made the suggestion that, when searching for parts, It Would Be Nice to have >>the system be smart enough to understand the standard metric suffixes so that >>when someone creates a part that's 100nF it can still be found whether someone >>searches for 0.1uF, 100nF, 100000pF, 1e-9F, or any other silly combination you >>might think up. > >All our resistors and caps are... believe it or not... IN ORDER BY >VALUE. That makes shopping for parts really nice. I also have a >program that finds resistors in stock that approximate desired ratios. Ours aren't, unfortunately (they were, until some inventory droid decided that that didn't make any sense). It only takes a look-up through a table to do the conversion, though.
From: krw on 1 Jun 2010 18:56 On Tue, 01 Jun 2010 19:59:28 +0200, Jeroen Belleman <jeroen(a)nospam.please> wrote: >On 06/01/2010 07:27 PM, Joel Koltner wrote: >> "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >> message news:7229069me1jv2t5schs2suda9p3j0trpql(a)4ax.com... >>> We have standardized on pF, nF, uF, and, sadly, mF. >> >> Yeah, mF does seem a little odd to me, but I can't think of any good >> reason why it should be, so at least when I'm thinking about it that's >> what I use. > >I don't see why mF should be any stranger than mH, mm, mOhm or anything. You don't remember mF and mmF, I suppose. >Although, when I wrote the value of Boltzmann's constant as 13.8 yW/HzK >somewhere, the editor found it necessary to change that into >1.38 * 10^-23 J/K. > >Not everyone is comfortable with the full range of prefixes, I guess. I don't like mF, either, because it isn't normally used.
From: Joerg on 1 Jun 2010 20:53
krw(a)att.bizzzzzzzzzzzz wrote: > On Tue, 01 Jun 2010 08:24:15 -0700, Joerg <invalid(a)invalid.invalid> wrote: > >> krw(a)att.bizzzzzzzzzzzz wrote: >>> On Sun, 30 May 2010 09:34:02 -0700, Joerg <invalid(a)invalid.invalid> wrote: >>> >>>> krw(a)att.bizzzzzzzzzzzz wrote: >>>>> On Sun, 30 May 2010 08:38:54 -0700, Joerg <invalid(a)invalid.invalid> wrote: >>>>> >>>>>> krw(a)att.bizzzzzzzzzzzz wrote: >>>> [...] >>>> >>>>>>> ... Even when I was >>>>>>> contracting (and paid big-$ overtime), management didn't appreciate my ROI >>>>>>> calculations on a second monitor (less than a week ;). >>>>>>> >>>>>> Sometimes they should look, they'd be surprised how much lower in cost >>>>>> projects can come in with external engineers. >>>>> Just add up the cost hiring of employees. The down side is that sometimes >>>>> contractors with the appropriate experience are hard to find, particularly >>>>> ones willing to work on-site. >>>> Yes, they are often hard to find. But they can be more loyal than >>>> employees. If an employee quits after a number of years he's gone. He >>>> can't be there for you even if he wanted to because he's got a new >>>> fulltime job, plus a family, and so on.. A consultant or contractor can >>>> usually be called in again. I had clients from the early 90's who called >>>> me in on a problem 15 years later. The fact that I have moved across an >>>> ocean in the meantime didn't matter, if you want to be found you can and >>>> will be found by them (I gave all of them my new address, just in case). >>> Consultants are more loyal because they can be bought. ;-) Employees really >>> want to be part of the family. They're going to live there, they might as >>> well be. >>> >> Yeah, but when an employee quits that's usually like a divorce. He or >> she is gone. I just had that happen with a company where one of their >> key engineers on the project quit and it did cause noticeable project >> delays. > > Certainly, companies tend to rely on a few people too much and documentation > too little. Then under-pay them. OTOH, it's also possible that they'll get > run over by a bus... > No kidding. One job I got almost had a sad reason. The analog dude at that company owned one of those Japanese death machines that could go from zero to 60mph in 4sec and to 120mph in another 10sec. At around 100mph the frame weldment decided it had enough of this and the bike broke in two. Due to at least three lucky circumstances he survived it. >>>> On-site, yep, that can be a problem. But when one thinks hard about it, >>>> how many times is that really really necessary? Most of the time clients >>>> just send me the whole chebang to diagnose in my own lab. Other times I >>>> fly out there for a few days. Sometimes it's a long trip, like one to >>>> Korea but that was necessary because I needed to train their engineers >>>> so that the EMI problems they had wouldn't happen again on their next >>>> design. >>> Tell that to managers. They like to think they're in control. They like to >>> think having someone on site puts them in control. I suppose if you don't >>> trust the person, at least you can make sure they put in the hours. >>> Conversely, being off-site can have its problems, too. The big-picture can be >>> missed, or expectations can be completely unrealistic. >>> >> That's why consultants must be great communicators and generalists. >> "What happens if the signal at port B doesn't .." ... "Oh, dang!" > > A lot of that is just another set of eyes. That's why good design reviews are > so important. I did that several times, even during interviews. Much of my work is just that, design reviews. Plus later the re-design of the more nasty chunks of the circuitry. I can safely say that some of the products would have otherwise become a financial disaster. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |