On Friday 14 October 2016 19:41:23 MC Cason wrote: > Gene, > > Inline > > On 10/14/2016 02:01 PM, Gene Heskett wrote: > > On Friday 14 October 2016 14:45:31 Chris Albertson wrote: > >> Typically 0.1 bypass caps REALLY to have to be physically close to > >> the load they are bypassing. Within a few millimeters. Cut the > >> leads short and bridge the power pins with the cap. > >> > >> Placing a larger cap farther away can't cause any harm but it is > >> not going to do the same job. > >> > >> Reason: The real world is not the same as theory. All caps have > >> an internal series resistance (ESR). Think of them as a cap and > >> resister in series and model them that way too when you design the > >> circuit. The ESR of a .1uF ceramic cap is nearly zero, but for the > >> tantalum, you need to look it up in the data sheet. > >> > >> Why physically close to the load. Wire has non-zero impedance. > >> Mainly in this case it is inductive. You need to minimize the > >> value of the inductor between the 0.1 cap and the device. > >> Apparently the manufacturer wants a low impedance power supply. > >> > >> Draw the circuit schematic with a the lead wire inductance and > >> cap's ESR shown then you can see that needs to be minimized. Don't > >> worry about space you candy 0.1 caps that are the size of a large > >> grain of sand > > > > Anyplace of note to source them? > > Here is one in a 01005 package (Metric 0402) 0.016"L x 0.008"W - > (0.40mm x 0.20mm) : > http://www.mouser.com/ProductDetail/AVX/01016D104KATUA/?qs=sGAEpiMZZMs >0AnBnWHyRQAwkDkDzLNakJDHmuCcZvLc%3d > > They are cheaper than the through hole caps that I normally buy. > Hand soldering them will be a royal PIMA! > At .2mm x.4mm, you have that right, the pain will be in My Ass. My hands are just starting to get nervous, which won't help a bit. And to see them well, I might have to get some cataracts removed. That is about the size of a comma in the newspaper! My hot air wand could blow it away, never to be found again by anything but the vacuum cleaner. That would fit across the gap between 2 traces, cut about as narrow as my mill could make them. This is going to be fun, for some definition of fun. I may even see if a bigger one, say about 1/8" long might be had. Those I have played with a wee bit.
Thanks MC Cason. > >> The usual way to mount these is to make a tiny PCB that has the > >> device on to and a mounting hole and the passive parts like the > >> capacitor(s) and a connector for the cable. I considered that, but the magnets in the 667's are strong enough to wiggle and crack the joints, so the 667s are super-glued to the bottom of their protective trench's. I'll have to reach a much bigger board a couple inches away with wire wrapping wire before it graduates to a 5 conductor cable to snake its way out of the back rear of the spindle housing. Stress relief & all that twaddle. :-) > >> > >> All that said, it will likely work OK if you can get that small ca > >> reasonably close. Better to get the 0.1 closer then a larger one > >> farther way as the goal is to minimize the amount of wire > >> > >> And using a larger cap is no substitute for the .01 either because > >> I bet the .1 was spec'd mainly for its low ESR, not because it > >> needed to be exactly 0.1uF > > > > As a CET, I am well aware of all that, including the inductance of > > 2" of wire. > > > > As for the ESR, tantalums are generally sub ohmic too. For half a > > century or more. Its reverse bias that nails them to the fence, even > > a few millivolts will do it eventually. > > > > Any caps on the leads will have to be not longer than the 667 is > > wide, and not more than half its thickness. > > > > Thanks Chris. > > > >> On Fri, Oct 14, 2016 at 9:51 AM, Gene Heskett > >> <ghesk...@shentel.net> > > > > wrote: > >>> Greetings everybody; > >>> > >>> A bit too cold this morning to go out to the shop and saw out the > >>> thicker spacers I am going to need to permanently mount the Z > >>> motor and screw anchor. > >>> > >>> So, not wanting to waste the day waiting for it to warm, I went > >>> back to work on the encoder thing this morning. > >>> > >>> I now have an additional tab of alu extending to the left to hold > >>> one of these ATS667's as an index pulse generator, and have that > >>> one s-glued in a bit beyond where the center of the glued on screw > >>> passes by, hoping it won't trigger on a regular tooth. > >>> > >>> But, I've never used any of these before. No clue as to their bad > >>> habits. > >>> > >>> The spec sheet I have shows a "required" .1 bypass to ground on > >>> the VCC lead, but has anyone had any problems using just one for > >>> all 3 devices? This thing is cramped for space for a bulky mylar > >>> .1. > >>> > >>> So I intend to put an even larger tantalum on the pcb, which will > >>> be on the left face of this added tab as I can let it project > >>> inward nearly 20 mm's in that space, lots of space before > >>> encountering anything that moves there. That means I'll have to > >>> paste some wrapping wire to extend the leads about 1" to get to > >>> the pcb. So this bypass cap may be as much as 2" of wire away > >>> from the device body. > >>> > >>> Can anyone testify that the extra lead length is a problem? > >>> > >>> Thanks all. > >>> > >>> Cheers, Gene Heskett > >>> -- > >>> "There are four boxes to be used in defense of liberty: > >>> soap, ballot, jury, and ammo. Please use in that order." > >>> -Ed Howdershelt (Author) > >>> Genes Web page <http://geneslinuxbox.net:6309/gene> > >>> > >>> ------------------------------------------------------------------ > >>>-- ---------- Check out the vibrant tech community on one of the > >>> world's most engaging tech sites, SlashDot.org! > >>> http://sdm.link/slashdot > >>> _______________________________________________ > >>> Emc-users mailing list > >>> Emc-users@lists.sourceforge.net > >>> https://lists.sourceforge.net/lists/listinfo/emc-users > > > > Cheers, Gene Heskett Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
