Why Is There No Good Search For Parametrically Similar Parts??....... - Page 1
Forum section: electronics / projects

author: Smokey
author_rank: Super Contributor
timestamp: April 28, 2023, 08:33:28 pm
content: Problem Example:A design calls for an obsolete part. Lets say an n-chan FET. Why is there no place where I can enter the part number and have it give me a list of the most similar parts across all parameters, with percent deviation for each parameter?With a report something like this...Original vs alternate part1:Package = 100% matchP = 99% matchVds = 98% matchId = 95% match...Vgs = 72% matchThen you can sort That list by your actual requirements based on what parameters are most important to your specific application.The distributors, like Digikey, already have databases with all the parameters (yes, I know they are incomplete and inaccurate in some cases). It's great that they have the feature now that lets you search for parts that have the identical parameters right from the original part page. But that fails if there are no matches with exactly identical parameters. But how often do you need exactly identical parameters?? If you want to search a range, you have to manually click all the values from the normal full parts search.I feel like every engineer needing to find viable alternate parts for some existing part would use the hell out of something like this. It would drive so much traffic to whoever makes that system.Does this thing already exist, and I just don't know about it? If so, let me know where it is and be my new personal hero....

author: jduncan
author_rank: Regular Contributor
timestamp: April 29, 2023, 03:20:58 pm
content: In theory you could do this with Octopart's API. But the data is so inconsistent it would be tough. When I built myself a tool to find in-stock generics (resistors/caps) I gave up on filtering by parameter and just used full text search.You need to verify all that against the datasheet anyway, I'm not sure it would save that much time. Setting up a parametric search in digikey is pretty quick.

author: tooki
author_rank: Super Contributor
timestamp: April 29, 2023, 07:19:40 pm
content: Quote from: Smokey on April 28, 2023, 08:33:28 pmIt doesn't give deviation or ranking, but alltransistors.com does search for substitutes based on parameters.I like your idea, though! I wonder where alltransistors.com gets its data...

author: donlisms
author_rank: Frequent Contributor
timestamp: April 30, 2023, 10:16:30 pm
content: I think an interesting interview question for software developers is about finding the closest match for an arbitrary RGB color, given a list of available colors. Algorithmically, it is essentially the same problem as you describe, with different variables. I think one very effective solution is to use something called a KD Tree, basically three (or however many) binary trees kinda woven together.I suspect most web designers have never heard of such a thing. Their conclusion is probably something like "It's too hard!" And that's the end of that!

author: vk6zgo
author_rank: Super Contributor
timestamp: May 01, 2023, 01:44:44 am
content: Quote from: Smokey on April 28, 2023, 08:33:28 pmJust finding a data sheet for a common but older part is hard enough.it looks easy, as you get lots of results, but many of them are shills for new "all, singing, all dancing" types of software to download PDFs.You click on what looks like it downloads the data sheet, only to be confronted with the thing trying to download something you don't want or need.Trying to find equivalents for Tektronix parts is pretty much "hit & miss"----mainly "miss"!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 01, 2023, 02:20:51 am
content: There is; you don't see them because they cost extra.Consider tools like SiliconExpert, which lists subs/alts as well as life cycle and distributor availability information. Think enterprise-grade Octopart.Or various places offering VAVE (Value Analysis and Value Engineering), same thing but with engineer(s) involved; PCB edits may be necessary, hence having more of a design team available is common. Also common with more broadly-featured CMs, assuming of course you're producing/paying enough to engage such a service. And, these will be more common with turn-key customers, i.e. who don't have much EE on hand themselves, so a CM with EEs is valuable.The percentage-match scheme you envision, I don't think exists, at least not from anything I've seen -- but replacements are usually more particular than that: either it's a drop-in sub, or an engineer needs to look at it and probably change some other things. And preferably an engineer is following along regardless, since it's easy to, say, cost-reduce a capacitor, only to find it fails on C(V) curve; someone should've looked! There's too many specs in too many disparate places, to organize all the parameters important for some application into such an easily viewed form.The closest would be services like these, which have enough scale to scrape such info into their databases; you still won't find everything, I think. Still, they're helpful.Tim

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 01, 2023, 02:59:37 am
content: Quote from: jduncan on April 29, 2023, 03:20:58 pmI agree there. While it may look like a very good idea with a relatively simple solution, distributors' web sites are full of errors and I would never rely on this data.It could still be useful to pre-screen a list of candidates that you would then check more closely using the datasheets. Don't know how much time it would save in practice, as you said.The real work, IMO, if there's enough interest for such a tool, would be to build a well checked, curated database of potentially millions of references.The software tools to tap into this database would be the easy part.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 02, 2023, 01:00:35 am
content: Particularly in the case of discrete components, manufacturers often use devices "because they have a lot of them", where the characteristics of the device in some positions are non-critical.Many years ago, Telecom Aust had a particular piece of equipment made "in-house" by the "Telecom Labs".The designer previously worked at Fairchild Semiconductors & for some reason or other, liked to use their products.When the equipment failed, we found that one of these devices, in a critical application, was the culprit & immediately started "chasing up" a replacement, only to find a long wait time for a genuine one, & equivalents non-existent. (The "lots of 'em" that the Labs had were already used up!)We were just about to set the ordering procedure into motion, when, looking over the rather sketchy parts list, I discovered they also used the same "special" device to turn an indicator LED on.Stealing that device for the critical spot, we fitted a BC108 to turn the LED on, & had the equipment back in service.