Are terminal Blocks always this loose?

Thread Starter

NVZN1

Joined Dec 17, 2016
18
So, this thing called terminal blocks, right? That green box, with screws, and u are supposed to insert the wire, then screw it tightly, yes?

Maybe im doing this worng or not, i always do tight screw it, but when i move it, it gets slowly loose. Maybe there's better way or anything? And yes i use these in portability.

IMG_20190808_185401.jpg
 

AlbertHall

Joined Jun 4, 2014
8,315
Can you take a picture showing the inside of the connector where the wires enter (with the wires screwed in).
 

MrChips

Joined Oct 2, 2009
19,270
What you show in the photo is an adapter. It is recommended for temporary use only.

BTW, your exposed wires are too long.
Cut the exposed part such that the plastic insulating cover is flush against the green part. No part of the exposed wire ought to be visible.
 

Thread Starter

NVZN1

Joined Dec 17, 2016
18
What you show in the photo is an adapter. It is recommended for temporary use only.

BTW, your exposed wires are too long.
Cut the exposed part such that the plastic insulating cover is flush against the green part. No part of the exposed wire ought to be visible.
the wire is exposed because it became loose. at first, the wires isnt visible, only insulators. and then, when i carry around, it became loose so it got little backwards, exposing the wire..
 

Thread Starter

NVZN1

Joined Dec 17, 2016
18
so there's no way to make this not loose again? i'm tired need to re-tighten the screws after i bring somewhere. Spade connectors cant fit in those too. sad.
 

hexreader

Joined Apr 16, 2011
375
Looks to me as though you may have over-twisted the wire before insertion. A gentle twist just to help bring stray strands back to the core is OK, but too much twisting is bad. When the wire un-twists it gets longer and thinner, causing the problem that you see.

That connector is poor quality (but I know of no good quality equivalent) and it is hard to tighten the screws well. Make sure your screwdriver is a good fit for the screw.

For a better connection, buy a plug that comes moulded onto a cable and do your temporary connection at the other end of the cable.
 

MrChips

Joined Oct 2, 2009
19,270
Are you tinning the end of the wire with solder? If so, don't.

A better technique would be as follows:

1) Strip off the outer insulation to leave the exposed wire longer than what you really need.

2) Tin the end of the wire with solder but leave about 5mm closest to the insulation solder free.

Or you can solder the entire exposed part and then strip off an extra 5mm of insulation.

3) Cut the soldered end to the exact length as required after insertion.

This will leave a flexible part for the screw clamp to depress.
It will also leave a hard soldered knob on the end which will resist withdrawal.
 

nsaspook

Joined Aug 27, 2009
6,265
Last edited:

Analog Ground

Joined Apr 24, 2019
152
Use ferrules, switch to solid wire or solder on a short piece of solid wire. In general, this type of connection is not recommended for stranded wire. The strands will settle into a different shape over time, especially if the wire is shaken or flexed, and the connection will loosen.
 

djsfantasi

Joined Apr 11, 2010
5,579
Use ferrules, switch to solid wire or solder on a short piece of solid wire. In general, this type of connection is not recommended for stranded wire. The strands will settle into a different shape over time, especially if the wire is shaken or flexed, and the connection will loosen.
I’ve used the method suggested by Analog Ground. This is the procedure I use:
  1. I strip the stranded wire, about 1/2” long. Try to strip it so that there is only a tiny separation in the insulation. Do not pull the insulation off.
  2. Place a short piece of heat shrink tubing over the stranded wire at this point
  3. Bend the stranded wire 90° at the insulation break
  4. Remove the insulation from the stranded wire by twisting it off. This neatly twists the strands.
  5. Then strip a solid conductor that fits into the screw terminal, about 3x to 4x the depth of the terminal.
  6. Holding the stranded wire against the solid conductor, neatly twist it around the bare wire.
  7. Solder the two wires together
  8. Trim any excess wire to the solder joint
  9. Slide the heat shrink over the soldered joint. It should extend over the insulation on the stranded wire and end at the end of the solder joint near the terminal end.
  10. Finally, trim the solid conductor so that when the wire is inserted, the heat shrink tubing is just at the opening.
Besides serving as insulation, the heat shrink also acts as stress relief.
 

ebeowulf17

Joined Aug 12, 2014
2,940
I've wondered about these issues numerous times, and every time I search for answers, I seem to find a dazzling array of conflicting opinions. Surely some manufacturers with good, smart R&D departments have studied all these issues and determined what the best practices are. Are there any datasheets, white papers, etc. that cover these issues?

In my case, what I'm most interested in is a similar, but slightly different style connector with what I believe are called "rising cage" screw-clamping systems, used in conjunction with 22 gauge stranded wire. We deal with this potential issue on several different parts, but here's one example for reference:

https://www.digikey.com/product-detail/en/on-shore-technology-inc/OSTTJ0411530/ED10556-ND/1588361
https://www.on-shore.com/part/osttjxx11530-terminal-block-pluggable-plug/
https://www.on-shore.com/wp-content/uploads/OSTTJXX11530.pdf

And here's a pic showing the "rising cage" portion of a similar part in two states - fully open on the left, and partially closing on the right:
upload_2019-8-9_6-33-6.png

As much as I value the opinions of all the experienced members here, I'd really like to see something more definitive. Can any of you direct me towards white papers, data sheets, or application notes that cover these issues?

Thanks!

P.S. If this is too much of a tangent from the current thread, I apologize. If the mods want to split this out into its own thread, I'm totally fine with that.
 

shortbus

Joined Sep 30, 2009
6,976
Maybe im doing this worng or not, i always do tight screw it, but when i move it, it gets slowly loose. Maybe there's better way or anything? And yes i use these in portability.
It still comes down to the TS using something in a way not consistent with the design of the product. The screws are to make electrical contact NOT wire retention. He is using the connector in a portable device moving the wires around, that is not what those terminals are made or designed to do. Even adding ferrules or tinning the wires won't change that. There is no "strain relief" built into the connection.

That same type of terminal block in the correct application would hold onto the wires just fine. It isn't that the screws are 'loosening', it's the wires pulling out do to movement of the whole wire length in use. The screws in any of that type block I've ever used don't make actual contact with the wire, they move a thin, smooth sheet metal part against the wire. And the smoothness of that lets the wire pull out, not grip the wire. It would be the same for a ferrule too.
 

nsaspook

Joined Aug 27, 2009
6,265
It still comes down to the TS using something in a way not consistent with the design of the product. The screws are to make electrical contact NOT wire retention. He is using the connector in a portable device moving the wires around, that is not what those terminals are made or designed to do. Even adding ferrules or tinning the wires won't change that. There is no "strain relief" built into the connection.

That same type of terminal block in the correct application would hold onto the wires just fine. It isn't that the screws are 'loosening', it's the wires pulling out do to movement of the whole wire length in use. The screws in any of that type block I've ever used don't make actual contact with the wire, they move a thin, smooth sheet metal part against the wire. And the smoothness of that lets the wire pull out, not grip the wire. It would be the same for a ferrule too.
I agree that the electrical connection should not also be the mechanical connection but ferrules are a huge improvement on stranded wire terminal block connections. Most good ferrule crimpers also ridge the surface of the connector barrel for better gripping strength (the metal is under compression/tension) inside the terminal wire clamp.
 

Thread Starter

NVZN1

Joined Dec 17, 2016
18
I agree that the electrical connection should not also be the mechanical connection but ferrules are a huge improvement on stranded wire terminal block connections. Most good ferrule crimpers also ridge the surface of the connector barrel for better gripping strength (the metal is under compression/tension) inside the terminal wire clamp.
anyway how these get in terminal screws? that looks long, maybe will expose some metals oputside the box terminal
 
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