What about using this style connector. They can be unplugged with has
the advantage of the board not being stressed when the wires are screwed
in. They need a simple square hole cut out. We use them & they look
professional.
http://www.rapidonline.com/catalogueimages/module/M074990P01WL.jpg
George Herold said:Hey it doesn’t look too bad...
https://www.dropbox.com/s/ou7imf0o66q880f/DSCF0030.JPG
(The hole will be smaller.. now I just gotta find room for two screws.)
Thanks all.
What about using this style connector. They can be unplugged with has
the advantage of the board not being stressed when the wires are screwed
in. They need a simple square hole cut out. We use them & they look
professional.
http://www.rapidonline.com/catalogueimages/module/M074990P01WL.jpg
This will for students making connections. There will be some strain
relief in the wires. But mostly I figure if they break it they can make
a new wire. I guess at some time the terminal block may break... but
that can be replaced by a competent tech. There will be some
disconnect-reconnect. We could go with just permanent wires.. but then
there are always wires flapping around. And the unit it attaches to
(an LED) will not be used all the time, so some way to disconnect would
be nice.
Hi George,
On 10/15/2013 10:59 AM, George Herold wrote:
Yeah I looked at some of those that John F posted. (I'll comment below)OK, I'm assuming you've effectively got a cable assembly of sorts
(even if it's just two loose wires) terminating at an LED, etc.
I.e., you are NOT connecting the component directly but, rather,
two "conductors" that you could space at whatever distance is
convenient for you/students.
I look at each solution in terms of something you could mount on the
*outside* of the box so that *it* would "hide your (fabrication) sins".
I.e., so you can drill an *approximate* hole to feed the connection
on the *back* side of the connector to your PCB.
First thought was a small (fine pitch) SINGLE ROW barrier strip with
ngish pins on the back side ("long" being defined by how far behind
the enclosure your PCB sits). For example:
<http://dgwelink.manufacturer.global...rrier-type/1068554164/9.5mm-barrier-strip.htm>
<http://www.digikey.com/product-detail/en/6-1437657-9/A98461-ND/1832527>
<http://www.digikey.com/product-detail/en/0387112202/WM7457-ND/3044561>
(I'm not endorsing any of these components -- just giving you an
idea of what I'm trying to describe)
Note that you should be able to let the *enclosure* provide the
mechanical support (instead of transferring those stresses onto
the PCB) as well as "hiding" the holes you drill through the
enclosure.
[Your PCB can have oversized holes through which the "pins" on
the back of the barrier strip protrude so a dab of solder holds
it electrically]
Along the same lines, someone makes what is essentially a "spade
lug" that is 'L'-shaped. I.e., if you fastened it onto a barrier
strip, you would end up with a ~3/4" metal *bar* sticking straight
up (a "wire" would typically be wrapped around the bar -- not
"wire wrap" -- and secured with solder). You could use these
with a regular barrier strip but flipped over (so the "bar"
goes down into the enclosure and provides the means by which your
signals come *up* to the barrier strip's contacts -- to mate wit
the individual conductors fastened there).
[Sorry, I can't find a reference -- I'm sure I have some in my
parts cache so perhaps I'll drag out a camera...]
The problems with "wire under a screw" approach are:
- captive screws so students aren't chasing down screws that
they've backed out too far ("Ooops! Where did it go??"
- getting wire around CAPTIVE screw in the presence of any
"barriers" (can be alleviated by some side entry connections)
- *strands* of wire bridging any barrier between connections
Another approach is to use binding posts. But I am not sure how
small they make these -- all of mine are intended for "rugged"
use and tend to be VERY large. These, however, tend to be
easier to use -- eliminating most of the above drawbacks.
<http://www.amazon.com/Monoprice-103324-Quality-Binding-Two-Piece/dp/B001TKE25E>
The "push terminals" on the back of some "stereos" and speaker
enclosures also could be of interest. Push, insert wire, release.
<http://www.mavin.com/store.php/products/grayhill-29-100-binding-post-120vdc-538>
<http://www.hobbyking.com/hobbyking/..._loaded_4mm_electrical_binding_post_pair.html>
We've already come to a solution. I'm sticking the TB on a pcb and
bolting that to the panel from under neath. This does leave a bit of
ugly showing (No square inside corners on the milled slot.
But that doesn't bother me at all. (I'm all for functionality, my boss
worries about the aesthetics.)
The other issue I have with screws is the wire gets stressed and then
breaks as it wraps around the screw.
I really like these little Weidermuller terminal blocks we have.
They've got a nice machined action, and just 'grab' the wire top
and bottom.
Yeah too big. I feel required to put binding posts at 3/4" spacing.
Ohh, those last are 'sexy' looking. (If binding posts turn you on :^)
Hi George,
Use a punch/hot knife? Alternatively, deliberately *round* the
corners of the terminal block??
OK. :> I try to cheat to make cosmetics less of an issue
(i.e., front mounting things so ugly/misaligned holes are
hidden)
Yup. I really only like screw terminals for things you are going to
access infrequently. All of the above have bitten me *frequently*
(esp with household wiring -- e.g., #12AWG on a switch/receptacle)
Yes, that's what I meant with my "side entry" comment (then I
thought about it and realized they're *all* "side entry" in
some sense :< )
Learn to break those preconditioned responses! :>
If you are truly dealing with "students" (i.e., like a school "lab"),
then the cheapest and most effective (?) solution might be those
"springs" that served as quick wiring points in the electronic kits
of our (?) youth.
I.e., a tightly wound spring (one that can not be compressed any
further but, instead, can be *extended*) that is connected to your
circuit and mechanically supported thereby. User "bends" the
spring to one side thereby causing a gap to form between adjacent
coils of the spring. Insert wire into this gap. Then, release
the spring which causes it to bite down on the wire between those
coils (as they try to return to their original side-by-side
position).
Sorry, verbose description that isn't very visual. If you know
what I mean, then you KNOW what I mean! :>
OTOH, I have no idea if something like that is made commercially.
IIRC, the "kits" just pressed those springs into a sheet of
cardboard with the components "wired" to their undersides. Not
very robust yet still managed to survive lots of abuse!
These were/are hard to beat for student use:
http://en.wikipedia.org/wiki/Fahnestock_clip
http://www.abbatron.com/PDF/SD-539.pdf?
and are readily available:
http://www.newark.com/abbatron-hh-smith/539/fahnestock-clip-brass/dp/96F9060
Hi George,
Use a punch/hot knife? Alternatively, deliberately *round* the
corners of the terminal block??
Chuckle... Well I figure a binding post should have banana plugs built into the top and that *does* need a 3/4" spacing. (If there is some standard I find it best to use it.)Learn to break those preconditioned responses! :>
Uugh... No It's got to have a bit more 'class'.<snip rest of description>If you are truly dealing with "students" (i.e., like a school "lab"),
then the cheapest and most effective (?) solution might be those
"springs" that served as quick wiring points in the electronic kits
of our (?) youth.
Chuckle... Well I figure a binding post should have banana plugs
built into the top and that *does* need a 3/4" spacing. (If there
is some standard I find it best to use it.)
Uugh... No It's got to have a bit more 'class'.
We make 'high end' lab stuff. (Though this is a pretty low end product.)
http://www.teachspin.com/
Hi John,
These were/are hard to beat for student use:
http://en.wikipedia.org/wiki/Fahnestock_clip
http://www.abbatron.com/PDF/SD-539.pdf?
and are readily available:
http://www.newark.com/abbatron-hh-smith/539/fahnestock-clip-brass/dp/96F9060
TPC used to have batteries (24V?) with these as terminations.
As a kid, I didn't like them because continued use could result in
the "button" assuming a position "too depressed" to bite into the
wire. And, if you tried to remedy this by pulling up on the "button"
to return its "normal" position to something closer to intended,
you could overshoot, etc. The connector body just didn't seem
to retain its "springiness" as much as, for example, the "springs"
I cited.
[Though I recall the "dry cells" that I used had threaded studs
coming out for connections. And, knurled nuts that would secure any
wire wrapped around the stud... Last time I saw cells that big was
more than 20 years ago (courtesy of Gates, IIRC) ]
TPC used to have batteries (24V?) with these as terminations.
As a kid, I didn't like them because continued use could result in
the "button" assuming a position "too depressed" to bite into the
wire. And, if you tried to remedy this by pulling up on the "button"
to return its "normal" position to something closer to intended,
you could overshoot, etc. The connector body just didn't seem
to retain its "springiness" as much as, for example, the "springs"
I cited.[Though I recall the "dry cells" that I used had threaded studs
coming out for connections. And, knurled nuts that would secure any
wire wrapped around the stud... Last time I saw cells that big was
more than 20 years ago (courtesy of Gates, IIRC) ]
I remeber those, "Phone batteries" or IIRC "H cells" popular for
starting glow-plug model engines in the days before NiCd cells.
[Though I recall the "dry cells" that I used had threaded studs
coming out for connections. And, knurled nuts that would secure any
wire wrapped around the stud... Last time I saw cells that big was
more than 20 years ago (courtesy of Gates, IIRC) ]
Weren't they called BC cells? ("beer can" because of the size)
I recall them as "Number 6" batteries (cells). They were a fair bit
taller than a can of beer. More like a tall-boy (or maybe even
a bit taller).
Hi Jasen,
The "dry cells" (#6 IIRC) were large cylinders with threaded
lugs on top (one in the center, one out on the perimeter).
As the name states, it was a single "cell" (i.e., ~1.5V).
(there was also a "double lantern" battery -- more rectangular
like two lantern batteries glued side-by-side)
The phone battery of which I spoke was, IIRC, 12 D cells in a 3x4
array. One end of the string was brought out to one of these
"push-spring" connectors. The other end of the string was
similarly brought out -- along with "taps" for each of the
top 3 or 4 (?) cells in the battery. (i.e., you could adjust the
potential available by picking a different tap)
AFAIK, they were a WE product solely for CO use.
no. 731 "Big Jim", with terminal studs symmetrically placed in
the top. http://www.forbesbatteries.com/product_p/540.htm
I've hearde of something simmilar used for "battery C" (grid bias) in
valve sets, but IIRC one terminal was a flylead and the other a set of
sockets.
For some reason here they were putting pairs of No.6 sized cells at
the customer end of the line. I've seen he bakelite housings used.
