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From: Tim Wescott on 11 Aug 2010 11:55 On 08/11/2010 06:27 AM, Phil Hobbs wrote: > John Larkin wrote: >> On Tue, 10 Aug 2010 17:20:29 +0200, Fred Bartoli <" "> wrote: >> >>> Why are the so called PCB design experts just mouse shakers? >>> >>> Why does this have to happen during my holidays? >> >> Is the mouser distant from you? That's often a disaster. I prefer to >> keep the layout-er in the next cube, and stay close. >> >> Best next thing is to have a copy of his/her software and shoot the >> files back and forth often. I usually do the initial placement and the >> critical routing on, say, one channel, and stay close to the layout as >> it progresses. >> >> Some layout people place parts based on the rubberbands. That's >> usually a disaster. They have to place based on the schematic. >> Layer-layer crosstalk, trace widths, mechanical, thermal, pinouts... >> too many ways to mess up. >> >> I've always found women to be the best layout people. They seem to >> listen better. >> >> John >> > > Just had a slightly similar issue with a customer--an engineer who was > on his way out the door ditched the 0603 metal film resistors in favour > of 0402 thick films without telling anyone...>30 dB noisier down in the > 1/f region where we're working. > > There was plenty of room for the 0603s, but nooooo, he had to be creative. > > :( > > What a maroon. There may be enough pad space to bodge in 0603s for the > demo--I sure hope so. No 0402 metal films out there? That's the kind of lesson that one needs to learn by getting burned -- it's certainly not something that you're going to learn in school, and if you do it'll be one sentence in the middle of a 3rd- or 4th-year circuits class, and you won't even write it down in your notes because it won't be on the test. At times like these, it's best to remind yourself that you get paid by the hour (you _do_ demand payment by the hour to fix customer's screw ups, yes?), and the more they screw things up the more guaranteed income you get. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
From: Phil Hobbs on 11 Aug 2010 12:14 Tim Wescott wrote: > On 08/11/2010 06:27 AM, Phil Hobbs wrote: >> John Larkin wrote: >>> On Tue, 10 Aug 2010 17:20:29 +0200, Fred Bartoli <" "> wrote: >>> >>>> Why are the so called PCB design experts just mouse shakers? >>>> >>>> Why does this have to happen during my holidays? >>> >>> Is the mouser distant from you? That's often a disaster. I prefer to >>> keep the layout-er in the next cube, and stay close. >>> >>> Best next thing is to have a copy of his/her software and shoot the >>> files back and forth often. I usually do the initial placement and the >>> critical routing on, say, one channel, and stay close to the layout as >>> it progresses. >>> >>> Some layout people place parts based on the rubberbands. That's >>> usually a disaster. They have to place based on the schematic. >>> Layer-layer crosstalk, trace widths, mechanical, thermal, pinouts... >>> too many ways to mess up. >>> >>> I've always found women to be the best layout people. They seem to >>> listen better. >>> >>> John >>> >> >> Just had a slightly similar issue with a customer--an engineer who was >> on his way out the door ditched the 0603 metal film resistors in favour >> of 0402 thick films without telling anyone...>30 dB noisier down in the >> 1/f region where we're working. >> >> There was plenty of room for the 0603s, but nooooo, he had to be >> creative. >> >> :( >> >> What a maroon. There may be enough pad space to bodge in 0603s for the >> demo--I sure hope so. > > No 0402 metal films out there? Not above 100k, whereas we need 499k-750k. > That's the kind of lesson that one needs to learn by getting burned -- > it's certainly not something that you're going to learn in school, and > if you do it'll be one sentence in the middle of a 3rd- or 4th-year > circuits class, and you won't even write it down in your notes because > it won't be on the test. Not this guy. Both I and the main technical honcho there were very very clear about using metal film only. > At times like these, it's best to remind yourself that you get paid by > the hour (you _do_ demand payment by the hour to fix customer's screw > ups, yes?), and the more they screw things up the more guaranteed income > you get. Unless they disappear because they miss their milestones. Besides, these guys are smart, have great technology, and work really hard, so they deserve to succeed. (Besides, I'm constitutionally unable not to root for my customers. Waste and failure offend me deeply, especially when it's so unnecessary.) Current plan to make the demo milestone is to put 0603s on edge, diagonally across the pads. Growl. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: John Larkin on 11 Aug 2010 12:16 On Wed, 11 Aug 2010 09:27:13 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >John Larkin wrote: >> On Tue, 10 Aug 2010 17:20:29 +0200, Fred Bartoli <" "> wrote: >> >>> Why are the so called PCB design experts just mouse shakers? >>> >>> Why does this have to happen during my holidays? >> >> Is the mouser distant from you? That's often a disaster. I prefer to >> keep the layout-er in the next cube, and stay close. >> >> Best next thing is to have a copy of his/her software and shoot the >> files back and forth often. I usually do the initial placement and the >> critical routing on, say, one channel, and stay close to the layout as >> it progresses. >> >> Some layout people place parts based on the rubberbands. That's >> usually a disaster. They have to place based on the schematic. >> >> Layer-layer crosstalk, trace widths, mechanical, thermal, pinouts... >> too many ways to mess up. >> >> I've always found women to be the best layout people. They seem to >> listen better. >> >> John >> > >Just had a slightly similar issue with a customer--an engineer who was >on his way out the door ditched the 0603 metal film resistors in favour >of 0402 thick films without telling anyone...>30 dB noisier down in the >1/f region where we're working. > >There was plenty of room for the 0603s, but nooooo, he had to be creative. > >:( > >What a maroon. There may be enough pad space to bodge in 0603s for the >demo--I sure hope so. > >Cheers > >Phil Hobbs Get some of these! http://www.futureelectronics.com/en/Technologies/Product.aspx?ProductID=RG1005PBKITSUSUMUINTERNATIONAL8463069 John
From: Phil Hobbs on 11 Aug 2010 12:31 John Larkin wrote: > On Wed, 11 Aug 2010 09:27:13 -0400, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> John Larkin wrote: >>> On Tue, 10 Aug 2010 17:20:29 +0200, Fred Bartoli <" "> wrote: >>> >>>> Why are the so called PCB design experts just mouse shakers? >>>> >>>> Why does this have to happen during my holidays? >>> Is the mouser distant from you? That's often a disaster. I prefer to >>> keep the layout-er in the next cube, and stay close. >>> >>> Best next thing is to have a copy of his/her software and shoot the >>> files back and forth often. I usually do the initial placement and the >>> critical routing on, say, one channel, and stay close to the layout as >>> it progresses. >>> >>> Some layout people place parts based on the rubberbands. That's >>> usually a disaster. They have to place based on the schematic. >>> >>> Layer-layer crosstalk, trace widths, mechanical, thermal, pinouts... >>> too many ways to mess up. >>> >>> I've always found women to be the best layout people. They seem to >>> listen better. >>> >>> John >>> >> Just had a slightly similar issue with a customer--an engineer who was >> on his way out the door ditched the 0603 metal film resistors in favour >> of 0402 thick films without telling anyone...>30 dB noisier down in the >> 1/f region where we're working. >> >> There was plenty of room for the 0603s, but nooooo, he had to be creative. >> >> :( >> >> What a maroon. There may be enough pad space to bodge in 0603s for the >> demo--I sure hope so. >> >> Cheers >> >> Phil Hobbs > > > Get some of these! > > http://www.futureelectronics.com/en/Technologies/Product.aspx?ProductID=RG1005PBKITSUSUMUINTERNATIONAL8463069 > > John > Thanks. Those only go up to 100k, unfortunately, whereas there's a photodiode nonlinearity issue that we have to work around, hence the low photocurrents and attendant high resistances. There are the RG1608 and RGH1608 Susumus in 0603, which go up to 300k or so (1M theoretically, but nobody stocks them). Mouser has some 400k-ish ones. We might be able to fit 0805s on there if we really hold our breath. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: Phil Hobbs on 11 Aug 2010 12:36
Phil Hobbs wrote: > John Larkin wrote: >> On Wed, 11 Aug 2010 09:27:13 -0400, Phil Hobbs >> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> >>> John Larkin wrote: >>>> On Tue, 10 Aug 2010 17:20:29 +0200, Fred Bartoli <" "> wrote: >>>> >>>>> Why are the so called PCB design experts just mouse shakers? >>>>> >>>>> Why does this have to happen during my holidays? >>>> Is the mouser distant from you? That's often a disaster. I prefer to >>>> keep the layout-er in the next cube, and stay close. >>>> >>>> Best next thing is to have a copy of his/her software and shoot the >>>> files back and forth often. I usually do the initial placement and the >>>> critical routing on, say, one channel, and stay close to the layout as >>>> it progresses. >>>> >>>> Some layout people place parts based on the rubberbands. That's >>>> usually a disaster. They have to place based on the schematic. >>>> Layer-layer crosstalk, trace widths, mechanical, thermal, pinouts... >>>> too many ways to mess up. >>>> >>>> I've always found women to be the best layout people. They seem to >>>> listen better. >>>> >>>> John >>>> >>> Just had a slightly similar issue with a customer--an engineer who >>> was on his way out the door ditched the 0603 metal film resistors in >>> favour of 0402 thick films without telling anyone...>30 dB noisier >>> down in the 1/f region where we're working. >>> >>> There was plenty of room for the 0603s, but nooooo, he had to be >>> creative. >>> >>> :( >>> >>> What a maroon. There may be enough pad space to bodge in 0603s for >>> the demo--I sure hope so. >>> >>> Cheers >>> >>> Phil Hobbs >> >> >> Get some of these! >> >> http://www.futureelectronics.com/en/Technologies/Product.aspx?ProductID=RG1005PBKITSUSUMUINTERNATIONAL8463069 >> >> >> John >> > > Thanks. Those only go up to 100k, unfortunately, whereas there's a > photodiode nonlinearity issue that we have to work around, hence the low > photocurrents and attendant high resistances. There are the RG1608 and > RGH1608 Susumus in 0603, which go up to 300k or so (1M theoretically, > but nobody stocks them). Mouser has some 400k-ish ones. > > We might be able to fit 0805s on there if we really hold our breath. > Saved by an ace technician--he figured out how to get 0805s in there for the demo. :)) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net |