General > General Technical Chat

Pin header crimps that match SN-28B ?

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tooki:

--- Quote from: jpanhalt on July 26, 2021, 12:21:14 pm ---I just pulled apart a couple of connector on my bench.  Probably made about 5 years ago.  All crimps were done with the green handled crimper I showed earlier.

1) I categorize the "Berg" type, which is what you show and is sometimes called DuPont type, as being "indent" or "barb" retention.  The Berg type is in my mind a female "pin" with a cantilevered contact.   The company is now owned by Amphenol, I think.  The indent retention is a cantilever on the housing that pops into the crimped side.  The barb type has a barb on the non-crimped side of contact that pops into a hole on the housing.  I prefer the indent type.  They are easier to remove without any damage to the contact.

--- End quote ---
I feel this comment needs a lot of explanation.

What's depicted here are a Molex KK 254 (or clone) contact and an Amphenol (formerly Berg) Mini-PV contact.

What jpanhalt is talking about (for unknown reasons, since it wasn't the subject of the topic at all) is how the contacts are retained in the connector housings.

On most connectors with stamped contacts (including KK 254, JST XH, AMPMODU Mod series), the retention is via a barb somewhere on the contact. On most barbed contacts, it's on the bottom, but some have it on the top (like Molex SL and C-Grid III) or on the side (like AMPMODU HE13/HE14). On larger connectors, it's common to have multiple barbs.

On other connectors, like Mini-PV, JST PH, and the common Chinese "DuPont" (and the JST RE and RF series, which I suspect is the original that the Chinese DuPont clones are copies of), the barb is part of the housing, and clips onto part of the contact.


--- Quote from: jpanhalt on July 26, 2021, 12:21:14 pm ---2) The first photo shows a barb type retention, non-Berg contact at top.  The barb was pressed into the contact to get it released.  The bottom contact is a Berg type with indent retention.  It also has the pointed leaves as discussed earlier.  Notice, I clipped the very tips of the leaves off to facilitate crimping and insertion into the housing.

3) The second photo is a close up of the Berg-type connector.

--- End quote ---
Needing to trim the insulation crimp by cutting off the tips of the insulation crimp wings (they're called wings, not leaves) is a huge flashing red "WARNING, THIS AIN'T RIGHT" sign.

The pointy, asymmetrical crimp wings are intended to hug around the insulation, not bite into it. This is one of the key things 99.9% of the Chinese crimpers marketed for DuPont pins get wrong. This insulation wing type requires a circular insulation crimp die. (Whereas the symmetrical, flat-ended insulation crimp wings can be used with either a circular die to hug around the insulation, or with an m-shape die to bite into the insulation.) Ergo, any crimper with an m-shape insulation die is categorically incapable of correctly crimping a DuPont terminal, and indeed aren't even capable of crimping them in a minimally passable way.

This issue is all explained in detail in my thread that was already linked above: https://www.eevblog.com/forum/reviews/affordable-crimp-tools-for-small-connectors-(dupont-etc-)/

jpanhalt:
@tooki

As usual, no substantive input.  The reason the pointed leaves are cut is to fit a very tight housing when using a cheap crimper that cannot smoothly wrap  them.  Any overlap is too big.

How about showing those of us who don't know how, your successes using the same type of crimper and connectors with various mechanisms for insulation and retention, including but not limited to pointed leaves/wings?

tooki:

--- Quote from: jpanhalt on July 26, 2021, 02:24:20 pm ---@tooki

As usual, no substantive input.

--- End quote ---
Hmm, there seems to be no emoji for the gesture I have in mind.


--- Quote from: jpanhalt on July 26, 2021, 02:24:20 pm ---The reason the pointed leaves are cut is to fit a very tight housing when using a cheap crimper that cannot smoothly wrap  them.  Any overlap is too big.

--- End quote ---
I got that. But that doesn't indicate to you that something is seriously wrong?!?


--- Quote from: jpanhalt on July 26, 2021, 02:24:20 pm ---How about showing those of us who don't know how, your successes using the same type of crimper and connectors with various mechanisms for insulation and retention, including but not limited to pointed leaves/wings?

--- End quote ---
I dunno how many more times I need to say: the SN-28B is not suitable for crimping those terminals. I've explained why. I've created an entire multi-page thread discussing numerous affordable options. But no, I guess none of that is "substantive"…  ::)

I can't provide you any instructions for "successes" with DuPont contacts and an SN-28B because it's categorically impossible to achieve. Nor have I yet encountered any other contacts for a 0.1" header that are not mangled in some way or another when crimped in an SN-28B, since its jaws are too thick for small contacts. The closest to working are the KK 254 type, but it still damages the contact and wire.

Nor do I want to encourage people to try and wing it anyway: it's a bad idea, and given that there exist crimp tools for the same price that do a much better job, why screw around with the wrong tool? It's a fool's errand. So I'm not going to coddle you or anyone else by saying "oh, well you can press the SN-28B into service anyway and make do with it, here's how to make it 2% less sucky".

What I can do (and was actually in the process of doing when you responded) is to dig out my DSLR, macro lens, and flashes, then find and take pictures of various contacts as crimped with various crimpers, to show what good and bad crimps look like.


As for retention methods: huh? No part of that is up to the user as such; it's an inherent part of each connector design. Hence why I'm puzzled that you feel it needed discussion at all. You get the right contacts for a particular housing and that's that, the retention will work. (Provided you don't mangle the contact in the wrong crimper.) I'm not aware of any connector type where there were any choices of main retention mechanism. (Some connector families do offer optional secondary retention mechanisms that can be added on.)

tooki:

--- Quote from: 741 on July 21, 2021, 08:32:10 am ---I'd be interested to know if there are crimps (pins and also sockets) which work especially well with this tool.

--- End quote ---
Upshot is, no. The SN-28B is designed for much, much larger terminals, so it ends up mangling the contacts at the same time as not applying enough force to the conductor area, since it's just too big.

Read the big thread here https://www.eevblog.com/forum/reviews/affordable-crimp-tools-for-small-connectors-(dupont-etc-)/ for the best overview so far of both cheap crimpers and other websites with good info (there's a link there to a Matt somethingorother that has great info). But ultimately, it's almost like a sick joke, in that DuPont connectors are both the most common for hobbyists, yet also are one of the most fickle, needy contact types out there, with nobody producing a cheap tool that actually does a truly good job on them.

The TZ-4228B tool discussed in that thread is probably the closest so far. It's still not perfect (IMHO the DuPont crimps are a smidgen too loose with 24AWG wire; if I had to use it, I'd probably buy some thin-walled 22AWG wire instead), but it's the best so far of the ~$20 tools.

All else held equal, if you can instead use the KK 254 (or clone) type, I find its contacts to be far more tolerant of the tool choice (the TZ-4228B, the IWS-3220M, as well as various "D-sub" tools like SN-01BM/-02BM/-03BM, HT-255D, etc work well), but the contacts themselves don't loosen up after a few insertions the way most DuPont female contacts do. The downside is that it only comes as a single-row connector.

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