Can you tell what size resistors there are? - Page 1
Forum section: electronics / beginners

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: September 24, 2021, 05:01:43 pm
content: Can anyone tell from this photo what size resistors these are ?I can't tell if they are 0805 or 1206. I tried measuring them but can't seem to get accurate measurements this small.Thanks

author: magic
author_rank: Super Contributor
timestamp: September 24, 2021, 05:58:42 pm
content: 1206 is 3mm long, 0805 is 2mm long.The distance between pins of DIP package is 2.54mm.Looks like 0805 to me.Also, 1206 are twice as long as they are wide. They appear visually longer, these are more square which fits 0805 better.

author: james_s
author_rank: Super Contributor
timestamp: September 24, 2021, 06:01:27 pm
content: You need a caliper for measuring small things like that.https://www.harborfreight.com/6-in-digital-caliper-63711.htmlI agree they look like 0805 though.

author: magic
author_rank: Super Contributor
timestamp: September 24, 2021, 06:05:12 pm
content: Quote from: james_s on September 24, 2021, 06:01:27 pmTrue.Although mine doesn't need any of that "batteries" rubbish

author: bingo600
author_rank: Super Contributor
timestamp: September 24, 2021, 06:06:55 pm
content: Had the same thought 0805They fit between two "DIP" legs (long side)/Bingo

author: james_s
author_rank: Super Contributor
timestamp: September 24, 2021, 07:38:19 pm
content: Quote from: magic on September 24, 2021, 06:05:12 pmI have an old style mechanical dial caliper and a digital one, I like both for different reasons although I typically do reach for the digital one first because I can select millimeters, inches or fractional inches at the touch of a button, I'm just too lazy to convert what I read on the dial. Anything will work for this application though.

author: TimFox
author_rank: Super Contributor
timestamp: September 24, 2021, 08:59:02 pm
content: I had to give up on actual vernier calipers due to presbyopia, but dial calipers are still readable.The advantage to both vernier calipers and modern digital calipers is the English/metric selection.The experienced machinist at my former employer had a high-quality digital unit, but he always kept the batteries out of it when not in use.When going to an installation in Saudi Arabia, I left my good company-owned Mitutoyo digital calipers in Illinois and bought a metric dial calipers, since the temperature was going to exceed 40 deg C.

author: SpecialK
author_rank: Regular Contributor
timestamp: September 24, 2021, 10:06:58 pm
content: Probably 0805 as they have markings on them. A small possibility of being 0603. The odd 0603 is marked.It's good to get one of those PCB rulers with component footprints on it.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 24, 2021, 11:06:14 pm
content: You do not need calipers to measure things like that, but can easily do it from a picture.A simple method is to just use a screen ruler program, and then use something of a known size to calibrate your scale.For example, from the IC on the right you have 6 pin pitches in about 138 pixels, so each pixel is: 6*2.54/195 = 0.07815 mmThe SMT resistors are about 13 by 22 pixels, and that makes them about 1.0 by 1.719mmThese measurements are somewhat between 0603 and 0805.With a higher resolution (and well framed, taken perpendicular, etc)photograph, measurements can easily be made much more accurate.The simplest way to do this is load it in any pixel program and start counting pixels, but using a screen ruler is already a bit better. FreeCAD has the possibility to use a photograph as a background image, and then scale it precisely to some known size (for example the IC) and after that a sketch with accurate measurements can be laid over that.There is also commercial software for this, but I have not used it.Having good pictures is important for accurate measurements.

author: james_s
author_rank: Super Contributor
timestamp: September 25, 2021, 12:01:36 am
content: It's certainly possible to measure without calipers, but I would say that calipers are the correct tool to measure such things, and enable doing so quickly and easily. In addition they are perfect for measuring parts you have in your hand while you are drawing a PCB layout for them. Given the low cost of an entry level caliper there is not much reason to not own one.Friends of mine have owned a machine shop for years and they have some very nice calipers and other precision measurement tools. Most of the time they keep those locked up in the toolbox in the QA lab though, out on the floor most of the guys use a cheap set for day to day stuff. The cheap calipers are accurate enough for most jobs, and they're a lot cheaper to replace than the Japanese ones that are damaged just as easily if dropped or abused.

author: langwadt
author_rank: Super Contributor
timestamp: September 25, 2021, 01:34:13 am
content: Quote from: james_s on September 25, 2021, 12:01:36 amand if you ask most machinists they will probably tell you that calipers are not what you use for precision measurements

author: TimFox
author_rank: Super Contributor
timestamp: September 25, 2021, 02:52:24 am
content: Resolving the difference between 0603, 0805, and 1206 packages is not tool-room quality metrology.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: September 25, 2021, 03:34:26 am
content: I have a HarborFreight Digital caliper.Problem is, every time I measure it I can get a big enough difference to make it either 0805 or 1206. Fractions of a mm.If you can "accurately" measure within 1/10 of a mm consistently on a soldered SMD component less than 2mm on a side, , my hat's off to you. You have me beat.

author: james_s
author_rank: Super Contributor
timestamp: September 25, 2021, 04:25:02 am
content: Quote from: langwadt on September 25, 2021, 01:34:13 amIt depends on your definition of precision. Calipers are more precise than a machinists scale which is more precise than a tape measure, ruler or other measuring device the typical person is going to have but obviously they are not the ultimate in precision. They have a whole inspection lab that is climate controlled with all the expensive measuring devices but out on the shop floor there's a scale and a caliper at every machine station.

author: james_s
author_rank: Super Contributor
timestamp: September 25, 2021, 04:27:49 am
content: Quote from: ThermallyFrigid on September 25, 2021, 03:34:26 amIf you can't get it to consistently measure the difference between 0805 and 1206 there is something wrong with it. Mine can do it easily and is very consistent. I don't typically measure SMD chip components since I can eyeball the common sizes but I do use it frequently to measure pin pitch and diameter.

author: tooki
author_rank: Super Contributor
timestamp: September 25, 2021, 04:39:09 pm
content: Quote from: ThermallyFrigid on September 25, 2021, 03:34:26 amYou might not be able to accurately measure the short side (50 vs 60 mils really could be hard to measure, depending on whatever else is on the board getting in the way of proper angles), but the difference between the long sides is huge. The difference between 120 mils and 80 mils is far more than 1/10mm…

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 25, 2021, 11:13:46 pm
content: I've bought a bunch of cheap digital calipers and they all ended up in the garbage bin. Some even brand new and unused.The quality of those cheap ones vary, and a lot are just not worth using at all. I've had troubles with bad battery contacts, batteries falling out of the battery compartement, empty batteries whenever you want to use the thing, bad tolerances which cause them to not slide smoothly.So some years ago I bought a Mitutoyo and threw all the cheap garbage in the bin. and the Mitutoyo just works. should have bought one many years earlier.There is a middle ground though.The cheapest digital callipers you can buy are all crap and not worth the shipping costs. Apparently there are some reasonable quality digital calipers for a pricepoint around EUR40 but I have no personal experience with them. There are some reasonable good youtube video's with reviews of these things though.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: September 26, 2021, 12:08:24 am
content: Ok,I use a Caliper often enough to justify this purchase.I see them on Amazon for $111.00Thanks

author: SpecialK
author_rank: Regular Contributor
timestamp: September 26, 2021, 02:55:32 am
content: Quote from: ThermallyFrigid on September 26, 2021, 12:08:24 amWhy spend all that money when you could just buy a few components of various sizes for comparison? Like even in single quantity, 0603 and 0805 resistors would be like 10 cents each. Buy $2 worth and pay $8 shipping for a grand total of $10. Or add a few resistors to an order of $100 full of other supplies you might need and get free shipping.