How do you design these days?
in [Design]
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From: MooseFET on 3 Jan 2010 10:37 On Jan 2, 7:58 pm, krw <k...(a)att.bizzzzzzzzzzz> wrote: > On Sat, 02 Jan 2010 20:45:11 -0700, Jim Thompson > > > > <To-Email-Use-The-Envelope-I...(a)My-Web-Site.com/Snicker> wrote: > >On Sat, 02 Jan 2010 21:36:09 -0600, krw <k...(a)att.bizzzzzzzzzzz> wrote: > > >>On Sat, 02 Jan 2010 17:03:43 -0800, John Larkin > >><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > >>>On Thu, 31 Dec 2009 09:41:54 -0800, "Joel Koltner" > >>><zapwireDASHgro...(a)yahoo.com> wrote: > > >>>>"John Larkin" <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in message > >>>>news:7glpj5l1a7i5nm45bsp5gfhc016e3kjgo8(a)4ax.com... > >>>>> On Thu, 31 Dec 2009 09:10:22 -0700, Don Lancaster <d...(a)tinaja.com> > >>>>>>It is NEVER right the first time. > >>>>> We sell about 80% of our rev A boards, with no prototypes. Assuming > >>>>> the first unit won't work is self-fulfilling, and a good way to make > >>>>> sure the third iteration won't work either. > > >>>>I agree with your philosophy John... but you do allow yourself a non-zero > >>>>number of blue wires or a couple of tack-soldered components or something on > >>>>those saleable rev. A boards too though, right? > > >>>Sure, that happens. But it's supposed to be embarassing. > > >>>We make blue boards and I think we should use red wires. But > >>>production insists on blue. > > >>I know one company that does use red wires, so oops's stand out like > >>the sore thumb they are. > > >Isn't "blue wire" sort of a historic standard ?:-) > > In IBM they were known as "yellow wires", not matter what color. The > original Teflon WireWrap wires were yellow and the name was kept. I > don't even remember what color we use now. I tend to spec the part number with a -(any) on the end for color. Batch to batch from production will have different colors. The number of jumpers has dropped to maybe one or two at the most. The most common has always been the missed connection in the layout or schematic. If you call a power supply "+24V" in one place and "+24" in another, they are (no surprise) not connected. I now make it a rule to always check my supply naming as the last check before layout.
From: krw on 3 Jan 2010 11:38 On Sun, 3 Jan 2010 07:37:19 -0800 (PST), MooseFET <kensmith(a)rahul.net> wrote: >On Jan 2, 7:58�pm, krw <k...(a)att.bizzzzzzzzzzz> wrote: >> On Sat, 02 Jan 2010 20:45:11 -0700, Jim Thompson >> >> >> >> <To-Email-Use-The-Envelope-I...(a)My-Web-Site.com/Snicker> wrote: >> >On Sat, 02 Jan 2010 21:36:09 -0600, krw <k...(a)att.bizzzzzzzzzzz> wrote: >> >> >>On Sat, 02 Jan 2010 17:03:43 -0800, John Larkin >> >><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >>>On Thu, 31 Dec 2009 09:41:54 -0800, "Joel Koltner" >> >>><zapwireDASHgro...(a)yahoo.com> wrote: >> >> >>>>"John Larkin" <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in message >> >>>>news:7glpj5l1a7i5nm45bsp5gfhc016e3kjgo8(a)4ax.com... >> >>>>> On Thu, 31 Dec 2009 09:10:22 -0700, Don Lancaster <d...(a)tinaja.com> >> >>>>>>It is NEVER right the first time. >> >>>>> We sell about 80% of our rev A boards, with no prototypes. Assuming >> >>>>> the first unit won't work is self-fulfilling, and a good way to make >> >>>>> sure the third iteration won't work either. >> >> >>>>I agree with your philosophy John... but you do allow yourself a non-zero >> >>>>number of blue wires or a couple of tack-soldered components or something on >> >>>>those saleable rev. A boards too though, right? >> >> >>>Sure, that happens. But it's supposed to be embarassing. >> >> >>>We make blue boards and I think we should use red wires. But >> >>>production insists on blue. >> >> >>I know one company that does use red wires, so oops's stand out like >> >>the sore thumb they are. � >> >> >Isn't "blue wire" sort of a historic standard ?:-) >> >> In IBM they were known as "yellow wires", not matter what color. �The >> original Teflon WireWrap wires were yellow and the name was kept. �I >> don't even remember what color we use now. > >I tend to spec the part number with a -(any) on the end for color. >Batch to batch from production will have different colors. I've seen people who color code revisions (mostly in WireWrap, though) and power/ground/signal jumpers. I'll still use color coded wires for (the few) prototypes I do. >The >number of jumpers has dropped to maybe one or two at the most. The >most common has always been the missed connection in the layout >or schematic. If you call a power supply "+24V" in one place and >"+24" in another, they are (no surprise) not connected. I now make >it a rule to always check my supply naming as the last check before >layout. An easy check for this sot of error is a sorted netlist. Perusing a sorted netlist will find all sorts of otherwise difficult to find errors ('l's instead of '1's, '0'/'O',...). If a net is misspelled it'll show up twice.
From: John Larkin on 3 Jan 2010 13:08 On Fri, 01 Jan 2010 19:19:42 -0600, krw <krw(a)att.bizzzzzzzzzzz> wrote: >On Fri, 01 Jan 2010 17:40:54 -0500, ehsjr <ehsjr(a)nospamverizon.net> >wrote: > >>John Larkin wrote: >>> On Thu, 31 Dec 2009 11:49:37 -0800, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>> >>>>John Larkin wrote: >>>> >>>>>On Wed, 30 Dec 2009 20:02:02 -0800, D from BC >>>>><myrealaddress(a)comic.com> wrote: >>>>> >>>>> >>>>>>On Wed, 30 Dec 2009 20:01:39 -0600, "RogerN" <regor(a)midwest.net> >>>>>>wrote: >>>>>> >>>>>> >>>>>>>When I was in school components fit on solderless breadboards and we made >>>>>>>circuits using breadboards, power supplies, meters and oscilloscopes. Many >>>>>>>of today's components don't appear to be breadboard friendly, so how is it >>>>>>>done today? >>>>>>> >>>>>>>Is circuit design software and simulation good enough to go straight to a PC >>>>>>>board? Or do you use surface mount to breadboard adapters? Do you still >>>>>>>use a soldering Iron to solder or paste solder and an oven? >>>>>>> >>>>>>>I'm wanting to tinker with some circuits but some chips I'm interested in >>>>>>>only comes in MSOP or other packages that look intimidating to attempt to >>>>>>>solder. >>>>>>> >>>>>>>Thanks! >>>>>>> >>>>>>>RogerN >>>>>>> >>>>>> >>>>>>My motto: >>>>>>If it works on a breadboard, it's not worth producing. >>>>>> >>>>>>On my current project, I have to feed the simulator pcb parasitics and >>>>>>component parasistics to get accurate simulations. >>>>>>I've had to bench test to get some parasitics. Once parasitics are >>>>>>included, scope results and simulation results get close. >>>>>> >>>>>>If all looks good on sim, I make a pcb, etch it and bench test it. >>>>> >>>>>One problem is that device models often aren't available for fast >>>>>parts, or all you get are S-params when you need large-signal >>>>>time-domain stuff. So sometimes you can learn a lot by hacking some >>>>>FR4 and testing parts. >>>>> >>>>>I never breadboard entire products, or even complex circuits... just >>>>>enough to characterize parts or simple subcircuits. >>>>> >>>>>This is an EL07 driving a PHEMT... >>>>> >>>>>ftp://jjlarkin.lmi.net/BB_fast.JPG >>>>> >>>>>which made decent 5-volt, 1 GHz square waves. >>>>> >>>> >>>>How do you get those nice clean cuts into the copper? >>> >>> >>> Just x-acto. The magic trick is to then rub it hard with a Scotchbrite >>> pad. That removes the burrs. >>> >>> John >>> >> >>You've got a steadier hand than I'll ever have. >>I have to do it with a Dremel mounted in a drill press >>adapter, and slide the board against guides clamped to >>the bed. Even then ... :-( > >Sounds like you need a small milling machine. We had one of those PCB mills, on indefinite loan from a customer who wasn't using it. It was such a hassle that we wound up not using it too. I can do the modest stuff with a knife and some kapton tape. After that, it's easiest to just lay out a board and have a pcb house make a few. Teflon board material is a lot easier to x-acto than FR4. You can get it on ebay. John
From: John Larkin on 3 Jan 2010 13:19 On Sun, 3 Jan 2010 07:37:19 -0800 (PST), MooseFET <kensmith(a)rahul.net> wrote: >On Jan 2, 7:58�pm, krw <k...(a)att.bizzzzzzzzzzz> wrote: >> On Sat, 02 Jan 2010 20:45:11 -0700, Jim Thompson >> >> >> >> <To-Email-Use-The-Envelope-I...(a)My-Web-Site.com/Snicker> wrote: >> >On Sat, 02 Jan 2010 21:36:09 -0600, krw <k...(a)att.bizzzzzzzzzzz> wrote: >> >> >>On Sat, 02 Jan 2010 17:03:43 -0800, John Larkin >> >><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >>>On Thu, 31 Dec 2009 09:41:54 -0800, "Joel Koltner" >> >>><zapwireDASHgro...(a)yahoo.com> wrote: >> >> >>>>"John Larkin" <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in message >> >>>>news:7glpj5l1a7i5nm45bsp5gfhc016e3kjgo8(a)4ax.com... >> >>>>> On Thu, 31 Dec 2009 09:10:22 -0700, Don Lancaster <d...(a)tinaja.com> >> >>>>>>It is NEVER right the first time. >> >>>>> We sell about 80% of our rev A boards, with no prototypes. Assuming >> >>>>> the first unit won't work is self-fulfilling, and a good way to make >> >>>>> sure the third iteration won't work either. >> >> >>>>I agree with your philosophy John... but you do allow yourself a non-zero >> >>>>number of blue wires or a couple of tack-soldered components or something on >> >>>>those saleable rev. A boards too though, right? >> >> >>>Sure, that happens. But it's supposed to be embarassing. >> >> >>>We make blue boards and I think we should use red wires. But >> >>>production insists on blue. >> >> >>I know one company that does use red wires, so oops's stand out like >> >>the sore thumb they are. � >> >> >Isn't "blue wire" sort of a historic standard ?:-) >> >> In IBM they were known as "yellow wires", not matter what color. �The >> original Teflon WireWrap wires were yellow and the name was kept. �I >> don't even remember what color we use now. > >I tend to spec the part number with a -(any) on the end for color. >Batch to batch from production will have different colors. The >number of jumpers has dropped to maybe one or two at the most. The >most common has always been the missed connection in the layout >or schematic. If you call a power supply "+24V" in one place and >"+24" in another, they are (no surprise) not connected. I now make >it a rule to always check my supply naming as the last check before >layout. It helps to print out a net list and read it. If you see VREF and REFV, investigate! One mistake we used to make too often was swapping V+ and V- on opamps. Engineers tend to flip an opamp to make the feedback path look nice (different for inverting/noninverting) and that moves the power pins too. We check that really hard now. We *almost* made some boards that had the BGA pitch wrong, due to some metric/inch rounding error that got us 3/4 of a ball wrong across the whole chip. Caught that by accident before it got out. I'm always a little anxious until the first successful powerup, and then until the uP runs code, and then until the FPGA configures, and then... On a recent board, there came a point when Linux was talking through PCI Express to our FPGA, and everybody cheered. John
From: Michael A. Terrell on 3 Jan 2010 13:20
krw wrote: > > Michael A. Terrell wrote: > > > >krw wrote: > >> > >> Michael A. Terrell wrote: > >> > > >> > I wonder if Joerg demands at least one fire extinguisher in all his > >> >design contracts? :) > >> > >> Yeah, but he returns it, fully tested. > > > > Aka: EMPTY? > > "Ayup, it worked as designed!" Fire extinguishers usually do. ;-) -- Greed is the root of all eBay. |