Re-assignable DB9 Connectors? - Page 1
Forum section: electronics / general

author: TheWaterbug
author_rank: Contributor
timestamp: September 09, 2025, 10:59:42 pm
content: TL;DR: Help me find DB9 connectors with removable/reassignable contacts?I sell little modules for distribution, translation, and switching of (mostly) digital signals, typically with coax connectors:Sometimes my customers want to put a bunch of these in a rack mount chassis with mass-terminated connector(s), often D38999-style circular connectors. So we sell D38999 connector kits, with the coax cables terminated with a pair of D38999-style contacts, for the customers to insert into standard D38999 housings as they see fit:A single coax gets pinned out to two D38999 contacts for signal and shield/GND, and a pair of coax gets pinned out to three D38999 contacts for signal+, signal-, and common shield/GND. There is no "standard" pinout, nor even any standard for which pins are GND, which is why the D38999 is popular, because you can assign the pins any which way you want.Lately I've gotten several inquiries from customers who want to do exactly this, but with DB9 connectors at the edge of the box. Most DB9 connectors I've seen are solder-cup or PCB-mount, neither of which lends themselves to arbitrary re-assignment of pins in the way that D38999 contacts make possible. I can't just make a "standard" DB9 cable, because there is no standard for generic adaptation of signals if it isn't a serial COM port.I'm looking for a non-soldering solution, as this is for system integration folks who want to play with these like Legos™ before they commit to a final design.Do re-assignable DB9 connectors exist? I'd be looking for both genders, and both panel-mount and cable-end varieties for each, as there doesn't seem to any standardization on that area, either.Thanks!

author: themadhippy
author_rank: Super Contributor
timestamp: September 10, 2025, 12:25:23 am
content: this sorta thing?https://www.digikey.co.uk/en/products/detail/amphenol-positronic/M24308-2-1F/11617886

author: thm_w
author_rank: Super Contributor
timestamp: September 10, 2025, 12:35:04 am
content: Can't you wire each pin of the DB9 with say a female dupont crimp and then they can connect it to various points on the board?There is also stuff like this but not sure if its what you are asking for:https://www.aliexpress.com/item/1005009543087275.html

author: profanum429
author_rank: Regular Contributor
timestamp: September 10, 2025, 02:53:24 am
content: Quote from: themadhippy on September 10, 2025, 12:25:23 amYep, pretty sure this is exactly what he needs.Bonus, if you've got the crimper for 38999 contacts then you probably can just get a new positioner for M24308 pins/contacts.

author: jpanhalt
author_rank: Super Contributor
timestamp: September 10, 2025, 10:03:13 am
content: This is what I use:I got it from Amazon but can't find the exact thing this morning. It allows arbitrary male to female pin mappings with jumpers.

author: bitwelder
author_rank: Super Contributor
timestamp: September 10, 2025, 01:52:37 pm
content: There should be around also DB9-to-RJ45 adapters, where the DB9 side has the wires plugged already (so no need for a crimping tool), but you'll need to decide the DB9 slot for each pin. Then you'll use a regular twisted pair cable of appropiate length to go from one end to the other of your connection.

author: TheWaterbug
author_rank: Contributor
timestamp: September 11, 2025, 09:44:56 pm
content: Quote from: themadhippy on September 10, 2025, 12:25:23 amQuote from: profanum429 on September 10, 2025, 02:53:24 amYup! This looks to be exactly what I was looking for. I don't know why I didn't find it earlier. I suppose I was just using the wrong vocabulary.I'm going to order a few pieces and see how similar it is to 38999 assembly.Thanks!p.s. those other suggestions look interesting, but the far side of the sub-cables is going to be SMA.

author: MLXXXp
author_rank: Frequent Contributor
timestamp: September 12, 2025, 10:11:06 pm
content: Quote from: themadhippy on September 10, 2025, 12:25:23 amAnother alternative brand for the same (or similar) thing:https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=1308940_Sec8_amplimite&DocType=CS&DocLang=English&DocFilename=ENG_CS_1308940_Sec8_amplimite_0118.pdfI'm sure there are other brands out there, as well.And note that technically, it's DE9 (9 pins in an E size shell), not DB9, but DB9 has become popular and understood, just like JST is often used for other brands of similar but incompatible connectors.

author: tooki
author_rank: Super Contributor
timestamp: September 12, 2025, 10:30:00 pm
content: Quote from: TheWaterbug on September 11, 2025, 09:44:56 pmThere’s no special name for them — they’re just crimp-style D-sub connectors.The vast majority use compatible pins and housings. So shop around, including looking at the generic mil-spec part numbers for the contacts (M32029/64-369 and M32029/63-368 are the most common types, for male and female, respectively), as they may be cheaper. Molex/FCT also tends to be well priced.A few years ago I compiled a cross-reference guide for the contacts and tooling; I could dig it up if you need.A little pro tip for you, after some back and forth with one of the manufacturers about the difference between two seemingly-identical series of housings: some have metal contact retention clips, others do not. The ones with the clip can be used with both machined and stamped contacts, while the kind without the metal clips must be used with machined contacts.Since I like machined contacts better anyway, I just buy the M32029/64-369 and M32029/63-368 and use them with whatever housings I want.There are dedicated insertion/extraction tools for these, from $$$ tools from DMC all the way to disposable plastic ones that cost a dollar; all of these are defined in mil specs and so they’re widely available and the plastic ones are very cheap.

author: Cyclotron
author_rank: Unknown
timestamp: September 12, 2025, 10:34:21 pm
content: Quote from: MLXXXp on September 12, 2025, 10:11:06 pmSimilarly the "recommended standard" RS-232 is the actual standard TIA-232. But everyone knows what folks mean when they say RS-232.Another one is the common reference to ethernet cable ends as rj45 but they are actually Mod8 (8P8C). rj45 is an obsolete wiring standard.I purchased a set of male and females from amazon.https://www.amazon.com/dp/B0CBJYXZGJ?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_6&th=1

author: tooki
author_rank: Super Contributor
timestamp: September 12, 2025, 10:35:00 pm
content: Quote from: TheWaterbug on September 09, 2025, 10:59:42 pmWhat?!? They’re arguably among the most-standardized connectors on the planet. They’re very modular, so perhaps it’s not obvious to you that the connectors for panel- and cable-mount applications are the same. Fundamentally, you just attach the retention nuts, retention screws, and backshell to the respective parts as needed. (You can get some connectors with the nuts integrated or attached, which does reduce their flexibility. But most don’t.)

author: EPAIII
author_rank: Super Contributor
timestamp: September 13, 2025, 06:45:48 am
content: Knowing the correct search terms is called "Google Fu". We all get caught up by it at one time or many.Quote from: TheWaterbug on September 11, 2025, 09:44:56 pm

author: Cyclotron
author_rank: Unknown
timestamp: September 13, 2025, 03:29:32 pm
content: Quote from: EPAIII on September 13, 2025, 06:45:48 amI don't know if Google made it better or worse. I used to be a fan of"Altavista"and it was super important to get your boolean search terms and operators proper to get good results. I still use similar techniques with google but more relaxed.Use of AI search can be dramatically easier, but it remains to be seen if it is "better".

author: tooki
author_rank: Super Contributor
timestamp: September 13, 2025, 07:08:36 pm
content: Quote from: Cyclotron on September 13, 2025, 03:29:32 pmIt’s maybe better than the awful the-only-reason-you-search-for-things-is-shopping disaster that Google search has been turned into, but I don’t think it’s anywhere near as good as Google search was before they ruined it.One thing I never liked about Google search was the lack of robust support for Boolean search operators. They’ve only ever had half-assed support for them, and the enshittified Google now often ignores them if it can’t find anything.

author: KrudyZ
author_rank: Frequent Contributor
timestamp: September 13, 2025, 07:48:39 pm
content: Going from coax through a DB9 connector and back to coax will really mess with your signal integrity.If that is of concern then there are better solutions for this:https://www.molex.com/en-us/products/rf-microwave-technology/multi-port-rf-coaxial-cable-to-board

author: tooki
author_rank: Super Contributor
timestamp: September 13, 2025, 08:06:23 pm
content: Quote from: KrudyZ on September 13, 2025, 07:48:39 pmIf it works adequately with the M38999 circular connectors and ordinary pins, it’ll work with a D-sub and ordinary pins.And if it should become an issue, coaxial contacts (that fit into the normal connector cavities!) do exist.

author: tooki
author_rank: Super Contributor
timestamp: September 13, 2025, 08:49:55 pm
content: I just got around to looking atOP’s website. I wouldn’t be surprised if there are some of their products in use in the laser labs I support.But man, I wouldn’t have the balls to charge those prices — $23 for a 2-pin twisted-pair header cable, $29 for a pack of 10 zip ties…I get it that the core products aren’t mass-market products with large numbers of customers, but damn… no wonder my predecessors in the department built so much similar stuff (clock dividers, pulse transmitters, etc.) themselves!And similarly, I wouldn’t have had the balls to apply for the two patents they received (both expired by now), as they strike me as flagrant violations of the law applicable at the time:Quote(Pre-AIA means before the 2011 “America Invents Act” revision of the law.)Both patents apply to simple breadboard adapters (breakout boards), the likes of which existed long before they applied for the patents in 1999:https://patents.google.com/patent/US6407652B1/enhttps://patents.google.com/patent/US6265952B1/en

author: Cyclotron
author_rank: Unknown
timestamp: September 14, 2025, 12:00:17 am
content: Quote from: tooki on September 13, 2025, 07:08:36 pmThank you! You made me actually LOL. I lovethat termfor a means to quickly communicate how proper and good tools and applications have turned into big turds.You are of course 100% right. When Google started I got an early view of it from a friend that consulted on investments. He argued with me that Altavista would soon be wiped from the internet. The first time I plugged in a few search terms he told me that he'd pay me 50 bucks if I didn't accept the page that came up when if I pushed "I'm feeling lucky." He didn't pay me.It was pure math and pure magic to see. Then, as you say, Enshittification happened.Thanks again.

author: Cyclotron
author_rank: Unknown
timestamp: September 14, 2025, 12:03:56 am
content: Quote from: tooki on September 13, 2025, 08:49:55 pmI think your link to the OP is wrong?https://www.pulseresearchlab.com/is the one I think is right and the one in your post, lol, goes here:https://www.pulseresearch.com/Which I can see someone needing a lot of to sell some 29 dollar pack of 10 zip ties.Dang, that's twice in one thread I've litterally LOL'd.

author: tooki
author_rank: Super Contributor
timestamp: September 14, 2025, 05:10:07 pm
content: Quote from: Cyclotron on September 14, 2025, 12:03:56 amOops you’re absolutely right, thanks for the heads up. I’ll edit my post to fix it.