On Sunday, November 14, 2021 at 2:14:53 PM UTC-8, TTman wrote:> On 14/11/2021 18:27, jla...@highlandsniptechnology.com wrote:> > I have space on this one for a few more 0603s. It's inefficient to > > load a reel onto the pick-and-place just for one resistor.> Pots are your enemy...When mailorder is slow, and you have a triangle file and carbon comp resistor in play, it's time to declare armistice or maybe even peace. Remember, after filing the notch, to use some nail polish for sealing that surface... or job it out to a cosmetology shop.
juggling parts
Started by ●November 14, 2021
Reply by ●November 15, 20212021-11-15
Reply by ●November 15, 20212021-11-15
On Sun, 14 Nov 2021 21:34:51 -0800 (PST), whit3rd <whit3rd@gmail.com> wrote:>On Sunday, November 14, 2021 at 2:14:53 PM UTC-8, TTman wrote: >> On 14/11/2021 18:27, jla...@highlandsniptechnology.com wrote: > >> > I have space on this one for a few more 0603s. It's inefficient to >> > load a reel onto the pick-and-place just for one resistor. > >> Pots are your enemy... > >When mailorder is slow, and you have a triangle file and carbon comp >resistor in play, it's time to declare armistice or maybe even peace.Just buy a few sample kits. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Reply by ●November 15, 20212021-11-15
On Sunday, November 14, 2021 at 10:27:30 AM UTC-8, jla...@highlandsniptechnology.com wrote:> OK, but the little opamp works better. Same number of parts, much > smaller, more stable, uses available values. That's the game here.It's happy driving 4.7uF to ground? -- john, KE5FX
Reply by ●November 15, 20212021-11-15
On a sunny day (Sun, 14 Nov 2021 14:22:45 -0800) it happened jlarkin@highlandsniptechnology.com wrote in <ss23pgp37oil6tqviok9jpgaepnd9jn6lc@4ax.com>:>On Sun, 14 Nov 2021 22:14:47 +0000, TTman <kraken.sankey@gmail.com> >wrote: > >>On 14/11/2021 18:27, jlarkin@highlandsniptechnology.com wrote: >>> On Sun, 14 Nov 2021 17:59:06 GMT, Jan Panteltje >>> <pNaOnStPeAlMtje@yahoo.com> wrote: >>> >>>> On a sunny day (Sun, 14 Nov 2021 09:39:03 -0800) it happened >>>> jlarkin@highlandsniptechnology.com wrote in >>>> <1ch2pgh4echute3tflmia84j7uosmor4rv@4ax.com>: >>>> >>>>> On Sun, 14 Nov 2021 17:11:29 GMT, Jan Panteltje >>>>> <pNaOnStPeAlMtje@yahoo.com> wrote: >>>>> >>>>>> On a sunny day (Sun, 14 Nov 2021 08:39:13 -0800) it happened >>>>>> jlarkin@highlandsniptechnology.com wrote in >>>>>> <54e2pgl0ir9ucjhtrcq35c0dj7pkadrgf8@4ax.com>: >>>>>> >>>>>>> >>>>>>> Once you have a few resistors on a schematic, it's tempting to do what >>>>>>> you want using existing values. That reduces the BOM and the >>>>>>> pick-and-place setup. There are far more possibilities if you are >>>>>>> willing to compromise things some, or put resistors in series and >>>>>>> parallel. This is a 4-page schematic with 9 different resistors. Doing >>>>>>> this is an enormous PITA. >>>>>>> >>>>>>> https://www.dropbox.com/s/aozh6m6mmmik6lb/T502_Parts.jpg?raw=1 >>>>>>> >>>>>>> Saved a DAC reference chip! Actually, having the DAC voltage >>>>>>> ratiometric on +15 is a benefit here. >>>>>>> >>>>>>> That opamp should be stable with the tantalum load and a 1u ceramic at >>>>>>> the DAC, but I'll verify that. >>>>>> >>>>>> Or a second LM317 for the +3V? >>>>> >>>>> Yuk! That would involve an entire new chain of value juggling. >>>> >>>> Really? >>>> >>>> >>>>> The resistor ratio needs to be 1.4:1. I can get 3.125 volts with three >>>>> resistors. >>>> >>>> What I do not get is: you sell expensive things in low quantity and try to save on a trimpot? >>> >>> Trimpots are expensive and need manual turning. DACs are automated and >>> can have cal factors stored in cal tables. I'm using 16-bit DACs and >>> there are no 16-bit trimpots. >>> >>> Some of my customers absolutely forbid trimpots, which I think is >>> extreme. Once in a while they make sense. They say that if there's a >>> pot, their techs will turn it. >>> >>> >>>> or waste board space with funny resistor combinations? >>> >>> I have space on this one for a few more 0603s. It's inefficient to >>> load a reel onto the pick-and-place just for one resistor. >>> >>> The LM317 is huge. >>> >>>> I mean I use 3 resistors to get a LM317 to output some specific voltage all the time.. >>>> mostly different ones. >>>> Sure you can use 1 Ohm resistors to do most things, but then you need many,,,, >>>> 10 Ohm would work too here. >>>> >>>> >>>>> The +15 charges a timing ramp through resistors, and the DAC feeds >>>>> some timing comparators, so it's nice if they are ratiometric. 317's >>>>> are not very good references. >>>>> >>>>> Data sheets suggest that an LM317 can't make 3 volts from 5 volts, so >>>>> I'd have to power it off +24. >>>> >>>> Power it from the 15V you made with the first one. >>>> >>> >>> OK, but the little opamp works better. Same number of parts, much >>> smaller, more stable, uses available values. That's the game here. >>> >>> >>> >>> >>> >>Pots are your enemy... > >When I see a schematic full of trimpots, it's a sure bet that the >author doesn't understand things. > >The Review Of Scientific Instruments is full of trimpots. And >diffamps. And current mirrors.I'd rather be on mars with a box of trimpots to fix the return craft than being stuck not having that 1k2 resistor.
Reply by ●November 15, 20212021-11-15
On 15/11/2021 16:34, whit3rd wrote:> On Sunday, November 14, 2021 at 2:14:53 PM UTC-8, TTman wrote: >> On 14/11/2021 18:27, jla...@highlandsniptechnology.com wrote: > >>> I have space on this one for a few more 0603s. It's inefficient to >>> load a reel onto the pick-and-place just for one resistor. > >> Pots are your enemy... > > When mailorder is slow, and you have a triangle file and carbon comp > resistor in play, it's time to declare armistice or maybe even peace. > > Remember, after filing the notch, to use some nail polish for > sealing that surface... or job it out to a cosmetology shop. >Barbarian, using a triangle file, think of the mechanical stress concentration begging it to snap in half. Use a round chainsaw sharpening file or round needle file at least! I'd even consider drilling a few small holes part way through it would be more humane.
Reply by ●November 15, 20212021-11-15
On a sunny day (Sun, 14 Nov 2021 14:22:45 -0800) it happened jlarkin@highlandsniptechnology.com wrote in <ss23pgp37oil6tqviok9jpgaepnd9jn6lc@4ax.com>:>When I see a schematic full of trimpots, it's a sure bet that the >author doesn't understand things.In the older days trimpots were common for opamp offset compensation in many precision circuits. Not sure if modern opamps still have offset errors?>The Review Of Scientific Instruments is full of trimpots. And >diffamps. And current mirrors.Its the same with variable inductors, radios used to be full of those, now everything is done in sillycon. rtl-sdr USB stick as example.
Reply by ●November 15, 20212021-11-15
On Mon, 15 Nov 2021 15:15:25 GMT, Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> wrote:>On a sunny day (Sun, 14 Nov 2021 14:22:45 -0800) it happened >jlarkin@highlandsniptechnology.com wrote in ><ss23pgp37oil6tqviok9jpgaepnd9jn6lc@4ax.com>: > >>When I see a schematic full of trimpots, it's a sure bet that the >>author doesn't understand things. > > >In the older days trimpots were common for opamp offset compensation in many precision circuits. >Not sure if modern opamps still have offset errors?Some have a few uV offset and a few nV/degc drifts. But we cal things out in automated test, and save the cal table in flash, so don't need pots. Sometimes we even cal out tempcos, which takes longer but nobody is standing around watching. Turning trimpots to tweak tempcos is for masochists.> > >>The Review Of Scientific Instruments is full of trimpots. And >>diffamps. And current mirrors. > >Its the same with variable inductors, radios used to be full of those, >now everything is done in sillycon. >rtl-sdr USB stick as example. >-- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Reply by ●November 15, 20212021-11-15
On Mon, 15 Nov 2021 23:07:34 +1100, Chris Jones <lugnut808@spam.yahoo.com> wrote:>On 15/11/2021 16:34, whit3rd wrote: >> On Sunday, November 14, 2021 at 2:14:53 PM UTC-8, TTman wrote: >>> On 14/11/2021 18:27, jla...@highlandsniptechnology.com wrote: >> >>>> I have space on this one for a few more 0603s. It's inefficient to >>>> load a reel onto the pick-and-place just for one resistor. >> >>> Pots are your enemy... >> >> When mailorder is slow, and you have a triangle file and carbon comp >> resistor in play, it's time to declare armistice or maybe even peace. >> >> Remember, after filing the notch, to use some nail polish for >> sealing that surface... or job it out to a cosmetology shop. >> > >Barbarian, using a triangle file, think of the mechanical stress >concentration begging it to snap in half. Use a round chainsaw >sharpening file or round needle file at least! I'd even consider >drilling a few small holes part way through it would be more humane. >I haven't seen a carbon comp resistor in years. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Reply by ●November 15, 20212021-11-15
On Sun, 14 Nov 2021 22:19:59 -0800 (PST), "John Miles, KE5FX" <jmiles@gmail.com> wrote:>On Sunday, November 14, 2021 at 10:27:30 AM UTC-8, jla...@highlandsniptechnology.com wrote: >> OK, but the little opamp works better. Same number of parts, much >> smaller, more stable, uses available values. That's the game here. > >It's happy driving 4.7uF to ground? > >-- john, KE5FXOPA197 is c-load stable for small caps and for big ones. It should be OK with a tantalum... the ESR is about right. I'll test that before we release the board. We do have some specifically c-load stable opamps in stock that would drop into the same footprint, if it ever did oscillate. But horrors, another part on the BOM! Most rrio opamps seem to be stable with capacitive loads, certainly with big ones. I got rid of another resistor. So now I have 8 values on a 4-sheet schematic. That includes an interesting servo to bias the distributed amplifier. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Reply by ●November 15, 20212021-11-15
