Equi-Potential Base Strip?

Discussion in 'Electronics Resources' started by ue418, Jul 6, 2010.

  1. ue418

    Thread Starter New Member

    Jun 22, 2010
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    [​IMG]
    I continue to have a need, in the course of my invention's development, for what I would call a "terminal strip" or "base strip", but with one caveat: all the positions should be already connected together. And I'm not talking about the large black terminal strips with the exposed screwheads. I know there are jumpers for them, but the connections are unacceptable for me, and they are really too big and ungainly for my purposes. I'm also not talking about the white plastic "European Style" terminal strips (although if they sold jumpers for them, I might consider it).

    I'm attaching a picture of an MCVU product from Phoenix Contact. It's designed to mount on a panel or whatever, and there is a mating plug that you insert into it. The pitch is 3.81 mm, but anything from 2.5 mm to 7 mm would probably do. I called PC again today, expressed my need, and again they told me they don't have any such thing. I just need something similar to this (doesn't have to be "pluggable"...could be terminal block style), but where all the positions are already connected to each other internally.

    The reason I need this is that I have a "box" which might have a circuit board near one end that has an output (say...a regulated 12V voltage) destined for 3 components (maybe an electronic filter, a motor driver, etc.) on the other end of the box. And rather than find a way to divert the 12V output into 3 or 4 parallel outputs, and then run 3 or 4 separate wires across the box, it would be much cleaner and easier to just run one wire across the box, to some sort of a "landing area". This "landing area" is what I need. So the wire would come into one pole of the "equi-potential base strip", and then 3 or 4 wires would emanate from other poles to their corresponding nearby components.

    I keep running into this need, and yet, the guy at Phoenix Contact told me today that he has never had a request for such a thing. I don't really understand that. Maybe I am doing something wrong....LOL. But if anyone has any ideas for this, I am in great need of them! Thanks a lot.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Something tells me you are trying to do power distribution the hard way, but who knows?

    If all you need is to be able to plug the wire connector into the illustrated terminal strip, the you can just use the captivating screws to grab a set of jumper wires that short all the terminals together.

    If the current isn't too high, a .1" or .157" header can be placed over a big PCB pad that acts as a single large voltage source. You can get IDC or crimp pin terminals to mate with the header.
     
    Last edited: Jul 6, 2010
  3. ue418

    Thread Starter New Member

    Jun 22, 2010
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    1
    So, regarding your first suggestion, wouldn't that require every position - except the 1st and last - having the ends of two separate jumpers stacked beneath the screw? That sounds like trouble, not only in assembling but in reliability. And the jumpers would be very short, which makes things even more difficult. Can you think of a product with a pitch of 2.54, 3.81 or 5 mm that could be inserted into those holes simultaneously? If I had something like that, then I would be happy.

    Regarding your second idea, I thought of something along those same lines. The "big PCB pad" you mentioned would have to have equally spaced holes, all at the proper pitch, right? Where on earth could I find a PCB like that? Wait a minute, I'm looking right now at a Radio Shack 276-170 board that I've had lying around for years. It has a long pad all the way across, with holes together in groups of five! So, if I cut this board into several sections....hmmmm. I'm attaching a picture of it now.
    [​IMG]
    It also has many other groups of five holes - oriented vertically - connected together. So if I cut this up, I guess I could create many of these "equipotential pads", each of which I can solder a 5-position header into. Then maybe drill some mounting holes, and stand it off a bit. All this still seems like a LOT of work for something that should be a standard product.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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  5. ue418

    Thread Starter New Member

    Jun 22, 2010
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    Thanks Beenthere. I checked out those terminal strips, and they are very similar to what I have found at Radio Shack. The problem with those black plastic ones (with exposed screwheads), is that connecting to them is precarious. With solid wire, you're never sure it will remain tight, and with stranded wire, the wire moves as you are tightening it, and you feel you are cutting through strands. I just spoke with Molex and he says that there are spade connectors that can be screwed onto each terminal position. That would be a big improvement for me, as long as I can trust the spade connection to maintain solid contact and not come loose (even with some occasional vibration during transport of my machine).

    The EuroStyle strips would be better from a connection standpoint, yet there don't appear to be jumpers for them. The guy at Molex is looking into these things, and will get back to me. But again, all of this just seems more difficult than it should be. I am amazed that there are not products (even the more compact Phoenix Contact type of stuff) that have variations where all poles are internally connected.
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    The easy way out of that is to terminate each wire in a ring terminal and use one #8-32 screw and a nut to capture them and compress them for a reliable mass contact. The machine screw can be fitted through a hole in some non-conducting material to hold everything in one place (or wrapped in several layers of tape).
     
  7. retched

    AAC Fanatic!

    Dec 5, 2009
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    What I believe you are looking for is called a buss bar.
    http://www.newmarpower.com/Terminal_Strips_Bus_Bars/Terminal_Strips_Bus_Bars.html

    It has the same potential across the buss. and you can connect across the whole strip.

    Here are smaller versions. The main 12v can enter at any point, but you usually connect it at the side offset point. Weather you put 12v or GND there, it will be across the whole block.

    http://www.ecvv.com/product/2224074.html

    There are also easy PCB mount ways to do this. You make 1 nice wide trace, then drill the holes in the trace to put this type of unit:
    http://ca.digikey.com/1/1/12328-terminal-block-5-08mm-vert-3pos-ed120-3ds.html
    They are made so you can run seperate traces to each pin, but there is no reason you cant use 1 trace for all the points.
     
    Last edited: Jul 6, 2010
  8. ue418

    Thread Starter New Member

    Jun 22, 2010
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    That's close, retched...thanks. I just wish there was a "mini" buss bar, that would not only be smaller than this, but also would have "wire guard" or "elevator" style screw terminals, like those on PCB terminal blocks/headers. I don't relish the thought of having to crimp or otherwise attach the fork or ring terminals to all my wires.

    I seem to be in some sort of electronic "no man's land" with regards to my needs. Thanks again both of you.
     
  9. retched

    AAC Fanatic!

    Dec 5, 2009
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    The digikey one has that. You can use bare wire.

    And if you dont want to use a PCB, you can use a strip of copper, and drill the holes and solder it in.

    You can stick it into your proto board that you posted and your done.
     
  10. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
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    If you use terminal strips and spade or ring terminals, I'd recommend also using flat washers and star washers to clamp things down, then torque the screws properly. I've seen terminal strip screws come loose over time.
     
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