What is the proper way to keep molded-together paired wires (aka the red/black type) from "unzipping" from each other past a certain point? I have to seperate them (the positive and negative wires) for a short length at the ends to use in screw terminals, but I don't want them to just continue to peel apart completely. Can I use adheasive heatshrink to stop a running split?
Heat shrink tubing should work just fine. I would say even appropriately sized non-adhesive will be fine. It has its limits, but the level of force that would tear heat shrink tube would not be something wires should subjected to anyway.
I just don't want them unzipping like headphone wire.
Make knots into the cable ends.
You can joint them with a electro tape
Or try using cable tie
Or try nots on the end of cable end
But heatshrink is the way to go.
(Actually, I often just get standard "spaghetti" tubing and stretch it with long nose pliers and quickly run it over the cable before it can shrink itself fully back. Tricky, it's a skill, but makes a nice snug fit if you get it right.)
Do you know by any chance what size heat strink tubing would work for two-conductor 18 awg silicone insulated wire? Should I use the 3-1 or the 2-1 ratio type? Glue or nonglue?
Doesn't really matter. Just you standard single wall 2:1 shrinkage generic black poly olefin tubing. I keep sizes from 1/16" to 1/2" on hand.
But that is a tedious way to deal with the "Dupont" pins. Multi-way housings are readily available, you just lift the plastic tab and remove the pins, then insert them in the multi-way.
Since you are almost never going to replace the single pin housings, it doesn't matter much if the tab breaks off in the process.
It may seem tedious, but no more so that pulling pins. Besides these allow you to color code your connections AND give you a place to label the connector. A pin 1 indent is part of the shroud as well. The larger form factor is often a plus vs trying to grab a small block. When two are butted to form a severable connector, the pins seem to be less prone to falling out of the sockets.
Design spec is that every module and the front and rear panels have to be severable for individual replacement without soldering.
Remember, I'm designing a retail product and not some STEM class project so the design constraints are a little tighter.
How would he replace them individually anyway, since he superglued them. I don't see why he doesn't just use a 1x4 housing, unless that blue piece is planned to have some sort of mechanical retention (eg click-in) function.
The shrouds make the duponts very secure especially cable to cable. It's also simpler to slip a shroud over four pins at once instead of pulling & reseating four pins. From a production standpoint futzing with four small pieces is more labor intensive than slipping one piece over four ganged wires. Your way works, but for maintenance how do you label mating parts? Also, is pin 1 marked on those black housings? If no, how to notice a reversal? The bulk of the shroud also makes it unlikely to have a one pin offset.
PS:
What does everyone here do for mounting these itty-bitty cards - some with ZERO mounting holes? I've been 3D printing all sorts of crap, pretty much on a 1:1 basis every time I get a new form factor in. Some, like the SD card need to be securely mounted so you can insert and eject the micro SD, but there are NO HOLES to mount it with!
You mean like this:
The SD card slot is on the bottom left, hence the thick wall on the right by the screw. This card had holes, but 2.5 mm is too small for #4 hardware. We only stock #4 or #6.
Why not just use M2.5 mounting screws?
We don't STOCK M hardware. Got too many variants with #4 and #6 as it is. It's not just the screws. Then we have to get the tap drill and thru drills and taps and the screws in five lengths and the drivers and the nyloc nuts and the washers, stainless steel and red fiber. It just never ends.
Look at it this way, we maintain stock of #4 and #6, adding another size will add 50% to the parts I've got to kit and track. plus you can't just order 4 screws, you have to order all the hardware by 100's. It gets real expensive real fast to carry all the possible permutations. I can design & print a mount for less than what it costs to buy hardware. Have you priced simple ¼" spacers? How about $40 / 100ct bx!
"Why not use M2.5 screws?" he says! HA! (LOL)
Most boards I have seen are m3, m2.5 (rarely), or m2. I have never seen imperial # machine screws on modern production PCBs.
If you've never seen it, you've not been looking.
3mm = #4 thru = .125" = near enough +- 200um (+- .008"). Lots of stuff fits #6 too.
Ardunio UNO & Mega both mount perfectly with #4.
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