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Terminals and Connector Sizes

Discussion in 'General Electronics Discussion' started by rabbithutch, Feb 13, 2019.

  1. rabbithutch

    rabbithutch

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    Jun 22, 2018
    I'm a geezer (past 75) trying to learn a little about electronics. I've dabbled here and there but must admit that I know very little about the subject.

    I'm trying to put a couple of units that take 120 VAC input and convert it to 2 12 VDC power circuits. I plan to use these units to power LED circuits and an electrolysis rust removal setup. I don't have the terminals that I need and seek advice on what to buy. The unit has a terminal connector block with screws calling for N, L, G input and -V, -V, +V, +V output. The width of the terminal blocks is 7.4mm and the screw shaft diameters are 3.7mm. I thought I'd use the crimp type ring terminal connectors but seem to have problems finding any that are narrow enough overall to fit within the 7.4 mm width that have an inside ring diameter large enough for the screws to pass through. The power input cord is 18/3 and I planned to use 22 AWG outputs but could use larger diameter wire. My output wire is twisted copper.

    Am I trying to use the wrong type connector? If so, what should I use? . . . Forked? If ring connectors are OK, what size or specification should I shop for? M6 is too wide to fit the terminal space width but accommodates the screws. I checked online for specs on M5 and M4 which seem to OK width wise but the inner ring diameters won't accept 3.7 mm screws, unless my old eyes and feeble brain are missing something. Any help would be greatly appreciated. I can upload a pic of the terminal block if that will help. Can I do that with the Upload a File button shown on this panel?

    Thanks in advance.
    rh
     
  2. Bluejets

    Bluejets

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    Oct 5, 2014
    Show a photo of the terminal block.
    Quite possible wiring can be fitted without any terminal.

    N,L,G = Neutral, Line and Ground input A.C.
    -v,-v,+v,+v = 2 D.C. outputs of - and + possibly different voltage or current level.
     
  3. rabbithutch

    rabbithutch

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    Jun 22, 2018
    The unit's terminal block is in the pic attached.
    psu lugs.JPG

    I'll upload another pic of the unit's spec decal. I couldn't upload both in the same reply. Is there a limit on how many files can be uploaded or on the space they require?
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    This type of terminal doesn't necessarily require cable lugs. With stranded wire use electric wire ferrules. Non-stranded wire can be clamped directly.
     
  5. Bluejets

    Bluejets

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    Oct 5, 2014
    Even stranded wire will fit ok.
    If you're concerned about it, just solder the ends.
     
    Cannonball likes this.
  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    It will fit, but it is not good practice to not use ferrules. Especially on, but not limited to, the high voltage side.

    No, that is definitely bad practice. Solder is comparatively soft and from under pressure from the screw will flow over time thus weakening the connection.
     
  7. Bluejets

    Bluejets

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    Oct 5, 2014
    Never failed me in over 50 years.
     
  8. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Used to be standrad procedure - it no longer is.
    You may be interested in this reading.

    We also had a discussion on that topic in the past.
     
  9. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Personally, I'd use these Screenshot_2019-02-15-05-31-22-1.png

    I disagree it's not good practice to not use ferrules, particularly on plate type terminals like this. I often give strands a slight twist and when using small gauge wire, I just strip wire back longer and fold back to double up the wire before inserting in terminal.

    I do agree that relying on solder is not wise because it flows, and even blows apart under heavy loads.

    The input size is fine. The #22awg output conductors are likely too small. Especially if they are long runs.
    Idk what the amperage is, but I'd us much bigger wire. Perhaps #14 or larger.
     
  10. AnalogKid

    AnalogKid

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    Jun 10, 2015
    I was about to suggest a fork terminal, and T beat me to it. His image is one with the ends turned up.. These work best on terminal blocks that do not have a floating plate under the screw head; the turned up ends hook behind the screw head. With the plate, an all-flat terminal works better. Here is an image of one for #16-#14 wire with thin tines that works well in narrow blocks.

    [​IMG]

    ak
     
  11. rabbithutch

    rabbithutch

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    Jun 22, 2018
    Thanks for all the input. I really appreciate it. I don't have any experience of ferrules but will look into it.
    Yes, I considered fork connectors; but the question in the OP still is unanswered. What size connectors should I use that will fit within the constraints of 74 mm and 3.7mm?
     
  12. dave9

    dave9

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    Mar 5, 2017
    Tinning the wire has never been a problem for me, but with one crucial detail. The fastener MUST be torqued enough (more than usual) to pre-deform the solder until it is the wire copper itself bearing the load. This pre-flows the solder and there is no margin left for it to go anywhere and loosen the fastener.

    It is certainly easier and better advice to just say don't do it because you can't be sure what someone is going to do *exactly*.
     
  13. AnalogKid

    AnalogKid

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    Jun 10, 2015
    The barrel size is determined by the wire, and the wire size is determined by the current (or, for a line cord to a relatively small power supply, whatever line cord wire gauge you have). Separate from that, the fork/ring dimension is whatever will fit.

    ak
     
  14. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    My picture shows a sta-kon crimp lug size RA18-6FS which means 18awg wire and a fork that slides onto a #6 screw that has a diameter of .13in or 3.3mm It should fit perfectly.
    Edit: Yes the tips of the forks do turn up slightly, but they help hold the lug under the terminal when tightening.

    If you want to use larger wire like 14awg on a #6 screw, then look for a 14-6F lug.
     
    Last edited: Feb 15, 2019
  15. Bluejets

    Bluejets

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    Oct 5, 2014
    Perhaps, however a "discussion" and "conclusion" arrived at by one particular group does not necessarily mean an unmistakably correct solution.

    We've also had this discussion relating to soldered joints in meterboxes etc. and the ruling was " concerns do not apply". Now you can argue with the SAA but never did anyone any good before so I can't see any change on the horizon.
     
  16. FuZZ1L0G1C

    FuZZ1L0G1C

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    Mar 25, 2014
    As well as the bare (dressed) stranded wire, forked crimp-lugs, and tinned wire already mentioned above, another method is to first bend the wire into a "sheperd's crook" or loop.
    Then, provided the wire is thin enough (max 1.85 mm diameter), it follows the entire "channel" around the screw/terminal gap.
    The screw / plate combo would of course have to be completely removed, the loop squeezed in snugly to keep the screw-hole female thread clear, then clamp the wire down securely using enough force to avoid loosening or arcing.
    The "free" end of the wire is then trimmed as close as possible (preferably flush) with the terminal front, to avoid strands shorting with its neighbor.
    This method is ideal when working with solid-strand wire or twisted copper where strands are few.
    As for tinning, I generally tin if multi-strand (as in line cord), as those hair-thin wires have a nasty habit of working their way out past a plate.
    As mentioned, tighten until max (but don't strip the thread), which I've managed to do on several occasions. :rolleyes:
     
  17. TommyR

    TommyR

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    May 13, 2010
    Why not use a ring lug and be done with it.
    Assuming you can remove the screw(s).

    upload_2019-2-20_10-41-31.png
     
  18. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    That works too. I've also just snipped a little off the ring end to make a quasi-fork terminal.
     
  19. dave9

    dave9

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    Mar 5, 2017
    ^ Or drill or file out the ring hole if it's slightly undersized. Not really sure why this topic exists, anyone can just go to Digikey.com etc and pick the dimensions they need. Terminal strips practically always use a standard size which in this case means standard or metric screw # to determine hole size.
     
  20. TommyR

    TommyR

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    May 13, 2010
    Just be very sure that the lug you plan to buy and use will fit in your terminal junction block strip.
    Measure to be sure.
     
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