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Panel mount terminal block

D

Don Y

Hi George,

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.

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
longish 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 with
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>

You can also consider a pair of test leads terminating in "EZ Hooks",
minihooks, etc. and let students clip those to the *legs* of the LED.
(this would make it easy to try different LEDs to see how they perform)

A lot depends on the *specifics* of your application -- how heavy
the wire will be, how sensitive the signals, how "clumsy" the
students, etc.

Too early in the morning -- I'm fixating on the "color gizmo"
and trying to imagine a bunch of students "experimenting" with
them. :<

If, instead, you want a *product* with a "tethered" sensor, consider
a minijack with the "sensor" a prefabricated, replaceable assembly.

HTH. Time for my morning tea...

--don
 
G

George Herold

Hi George,



On 10/15/2013 10:59 AM, George Herold wrote:

Wow, Don I'm overwhelmed by your generosity.
We've already come to a solution. I'm sticking the TB on a pcb and boltingthat 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.)

I'' have the slot machined for a snug fit on the TB.
https://www.dropbox.com/s/dm8qz6uw4f853tk/DSCF0033.JPG
That helps keep it from rotating.
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>
Yeah I looked at some of those that John F posted. (I'll comment below)
(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...]

No, Don't bother. I think I see it.
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

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.
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>


Yeah too big. I feel required to put binding posts at 3/4" spacing.
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>

Ohh, those last are 'sexy' looking. (If binding posts turn you on :^)

Again much thanks,

George H.
 
D

Don Y

Hi George,

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.

Use a punch/hot knife? Alternatively, deliberately *round* the
corners of the terminal block??
But that doesn't bother me at all. (I'm all for functionality, my boss
worries about the aesthetics.)

OK. :> I try to cheat to make cosmetics less of an issue
(i.e., front mounting things so ugly/misaligned holes are
hidden)
The other issue I have with screws is the wire gets stressed and then
breaks as it wraps around the screw.

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)
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.

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 :< )
Yeah too big. I feel required to put binding posts at 3/4" spacing.

Learn to break those preconditioned responses! :>
Ohh, those last are 'sexy' looking. (If binding posts turn you on :^)

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!
 
L

Lasse Langwadt Christensen

Den onsdag den 16. oktober 2013 22.49.02 UTC+2 skrev Don Y:
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!

https://www.sparkfun.com/products/11822

-Lasse
 
D

Don Y

Hi Lasse,


Yes, very similar (the ones from the "kits" had one end at a slightly
smaller diameter that would wedge into a hole in the "cardboard".
The "shoulder" formed where the coil diameter *increased* to its nominal
size acted as a stop to prevent the coil from being pushed too far into
the cardboard.

I guess the components mentioned in your reference are intended to
be surface mounted? Seems like it would have been easy for them
to have one end of the coil terminate in a "pigtail" on the central
axis of the coil (for ease of thru-hole soldering).
 
D

Don Y

Hi John,


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) ]
 
G

George Herold

Hi George,



Use a punch/hot knife? Alternatively, deliberately *round* the
corners of the terminal block??

Nice ideas. We have all our panels made by a small company in NJ..(long story). And we'll just let them do it however they think best.
(Ya gotta take care of your vendors!)
Learn to break those preconditioned responses! :>
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.)
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.
Uugh... No It's got to have a bit more 'class'.<snip rest of description>

We make 'high end' lab stuff. (Though this is a pretty low end product.)
http://www.teachspin.com/

George H.
 
D

Don Y

Hi George,

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.)

Understood. At the very least, make it REALLY OBVIOUS if you're
doing something different (i.e., don't use 5/8" spacing and piss
off all those folks who *try* to cram a dual banana plug into them!)

I have a wireless telephone whose base unit has the same sort of
"slotted holes" on the back that a regular wall telephone has.
As such, I *assumed* it would mount on the traditional "wall jack"
(with the two "rivets"/studs to engage these slots).

Nope. Bozos opted to use a different spacing (for no apparent
reason). As a result, I had to fabricate my own "custom" mounting
plate once I discovered this screw-up! :<
Uugh... No It's got to have a bit more 'class'.

Understood. Put racing stripes on it! ;-)
We make 'high end' lab stuff. (Though this is a pretty low end product.)
http://www.teachspin.com/

OK. That wasn't apparent from your initial comment (I assumed
something like a school project).
 
J

Jasen Betts

Hi John,


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.
 
D

Don Y

Hi Jasen,

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.

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.
 
D

Don Y

Hi David,

[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).

Some years ago, I was involved in a project where the power supply
guys opted to use a bunch of similarly sized cells to give an
incredibly low output impedance for the 20V supply (which had
to deal with a 400Hz 20A load, repeatably) Made the power supply
ungodly heavy!
 
J

Jasen Betts

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).

yeah, I found this web site, the guy seems to be a fan, down
the bottom there's some (reproductions) "telephone" cells
with fahnestock clips.

http://www.prc68.com/I/No6.shtml
(there was also a "double lantern" battery -- more rectangular
like two lantern batteries glued side-by-side)

no. 731 "Big Jim", with terminal studs symmetrically placed in
the top. http://www.forbesbatteries.com/product_p/540.htm
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.

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.
 
D

Don Y

Hi Jasen,

no. 731 "Big Jim", with terminal studs symmetrically placed in
the top. http://www.forbesbatteries.com/product_p/540.htm

Yes. A "favorite" for heavy duty flashlights ("bolt" onto the
two studs and act like a handle to carry the whole thing)
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.

Dunno. An uncle ran a CO, here. Gave me a really nice annunciator
(metal bar suspended beneath a tuned wooden cavity which is then
struck by electromagnetically driven rod). It required quite a
bit of heft to pull the metal striker up onto the bar (coil was
the size of an adult fist). Of course, it ran off CO "battery"
which isn't the sort of thing you're likely to have available
elsewhere. So, he gave me a couple of these weird "multi-tapped
batteries" so I could excite the coil without having a genuine
power supply. When the batteries eventually died, I cut them
open and discovered all the "D cells" inside.
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.

No idea what they were intended for. I used to use them as a power
source when I was a kid (6-8 yo) to "experiment" with electricity.
They would run for *hours* (driving trivial loads like low voltage
incandescents) without any noticeable sag.

I don't remember them as rechargeable, though (if they were, I
don't remember *having* a charger!).
 
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