Component selection - Page 1
Forum section: electronics / projects

author: iMadScience
author_rank: Newbie
timestamp: November 06, 2022, 02:58:03 pm
content: There are countless choices for each component on websites like Digikey. For example, a 0805 0.1uf bypass capacitor, is produced by many manufacturers. What are some recommended approaches to learning how to look at the datasheet and find the exact optimal component from the website? Same for all other components like resistors, inductors, etc. Or are there some typically recommended options for common uses?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 06, 2022, 03:41:15 pm
content: Too many to enumerate; a book could be written but it wouldn't stay current for very long.Experience. Eventually you'll see most of the shady things, or omissions, they leave out for various reasons (anything from lazy to malicious).Figure out which parameters you're looking for every time, and try to spot them -- they're usually named consistently but sometimes they use different symbols, or only give the name/description not the symbol, or...Watch for erroneous units. Siemens when they mean seconds is common enough to ignore, but sometimes you'll see V copy-pasted down a column when it's supposed to be uA, or maybe nC when it should be pC or vice versa... etc.Be careful about characteristics, especially with things like inductors and capacitors. Caps, the loss isn't usually a problem as long as you're using the right type (electrolytic ain't never gonna do a resonant circuit, etc.), but there are cases where you need to know the current or voltage limits vs. frequency (maximize VARs for a compact/affordable resonant supply?). Likewise inductors, saturation is often either soft or abrupt with current (powder and ferrite materials respectively) so it pays to know how much you can run at for a given value, and the Q factor varies more dramatically with frequency (inductors generally have poorer Q than capacitors anyway so they're both more variable and more critical in the circuit overall).Tim

author: TimFox
author_rank: Super Contributor
timestamp: November 06, 2022, 04:15:41 pm
content: Also, be careful when choosing between ceramic capacitor types, since many popular dielectrics have large changes in capacitance with applied voltage.Good data sheets from reliable manufacturers will show this dependence in their catalog pages.This classic 1949 book from the WW II radar development is now well out of datehttp://www.introni.it/pdf/17%20-%20Components%20Handbook.pdfbut there are more recent books (with similar titles) that cover these topics for modern components.

author: ledtester
author_rank: Super Contributor
timestamp: November 07, 2022, 12:06:46 am
content: Adafruit has been doing a segment on her weekly program called "The Great Search" in which she explains how she goes about searching for a suitable component on Digikey.https://www.youtube.com/c/adafruit/search?query=great%20searchThis one deals with "common through-hole resistors":The Great Search: Common Through-Hole Resistorsand this one deals with inductors for boost converters:From the Desk of Ladyada - The Great Search at Digi-Key: Inductors!