I was wondering if anyone could explain connector pitch vs flat cable pitch.. 3M advertises their MDR series of connectors as being 0.050" pitch, which is the horizontal pitch between connector contacts. However, these Centronics style connectors have two rows (an upper and a lower row).

Their drawing shows that the spacing between IDC slots is 0.050", but I don't understand how an IDC connector with two rows of 0.050" pitch contacts (effective pitch of 0.025") can use a 0.050" pitch ribbon cable. Do MDR connectors take two 0.050" ribbon cables, on one top of another?

Thanks,
Doug

On Sat, 29 Mar 2014 11:11:56 -0700 (PDT), "Doug D."
wrote:

I was wondering if anyone could explain connector pitch vs flat cable pitch. 3M advertises their MDR series of connectors as being 0.050" pitch, which is the horizontal pitch between connector contacts. However, these Centronics style connectors have two rows (an upper and a lower row).

Their drawing shows that the spacing between IDC slots is 0.050", but I don't understand how an IDC connector with two rows of 0.050" pitch contacts (effective pitch of 0.025") can use a 0.050" pitch ribbon cable. Do MDR connectors take two 0.050" ribbon cables, on one top of another?

Which drawing? A quick Digikey search turns up, e.g., 10150-8000EE
which is a .050" IDC Wiremount Plug which Mass terminates to .025"
pitch flat ribbon cable. The drawing shows .025 contact spacing on the
wire side. Still, people do make mistakes on drawings every day so
there certainly could be one out there with incorrect dimensions.

On Saturday, March 29, 2014 2:45:52 PM UTC-4, Rich Webb wrote:
On Sat, 29 Mar 2014 11:11:56 -0700 (PDT), "Doug D."

Doug D. wrote:



I was wondering if anyone could explain connector pitch vs flat cable pitch. 3M advertises their MDR series of connectors as being 0.050" pitch, which is the horizontal pitch between connector contacts. However, these Centronics style connectors have two rows (an upper and a lower row).



Their drawing shows that the spacing between IDC slots is 0.050", but I don't understand how an IDC connector with two rows of 0.050" pitch contacts (effective pitch of 0.025") can use a 0.050" pitch ribbon cable. Do MDR connectors take two 0.050" ribbon cables, on one top of another?



Which drawing? A quick Digikey search turns up, e.g., 10150-8000EE

which is a .050" IDC Wiremount Plug which Mass terminates to .025"

pitch flat ribbon cable. The drawing shows .025 contact spacing on the

wire side. Still, people do make mistakes on drawings every day so

there certainly could be one out there with incorrect dimensions.

Hi Rich,

Thanks for your response. I'm interested in the 3M 10236-0210EC (Digikey #MRB36A-ND), which is a 36-contact, 0.050" IDC Wiremount Receptacle. The drawing on page 2 of their datasheet shows a 0.050" contact spacing, but I don't see how this can be. A 36-wire, 0.05" pitch cable should be (36-1)*0.05" = 1.75" wide. But the table in the datasheet says that the connector dimension "D" for this part is only 1.05". I don't see how a 1.05" wide connector can accommodate a 1.75" wide cable.

Doug

On Sunday, March 30, 2014 5:20:27 PM UTC-7, Doug D. wrote:

... I'm interested in the 3M 10236-0210EC (Digikey #MRB36A-ND), which is a
36-contact, 0.050" IDC Wiremount Receptacle. The drawing on page 2 of their
datasheet shows a 0.050" contact spacing, but I don't see how this can be. A
36-wire, 0.05" pitch cable should be (36-1)*0.05" = 1.75" wide.

There's a top row and bottom row of the connector; so, the connector width
A (from center of first to center of last contact) is (18-1)* 0.05"= 0.850
just as the drawing shows. The pitch of the WIRES is 0.025", the even
wires mate with a bottom-row and the odd ones with a top-row connector pin.

On Monday, March 31, 2014 9:45:02 PM UTC-4, whit3rd wrote:
On Sunday, March 30, 2014 5:20:27 PM UTC-7, Doug D. wrote:



... I'm interested in the 3M 10236-0210EC (Digikey #MRB36A-ND), which is a

36-contact, 0.050" IDC Wiremount Receptacle. The drawing on page 2 of their

datasheet shows a 0.050" contact spacing, but I don't see how this can be. A

36-wire, 0.05" pitch cable should be (36-1)*0.05" = 1.75" wide.



There's a top row and bottom row of the connector; so, the connector width

A (from center of first to center of last contact) is (18-1)* 0.05"= 0..850

just as the drawing shows. The pitch of the WIRES is 0.025", the even

wires mate with a bottom-row and the odd ones with a top-row connector pin.

Thank you, that's what I was afraid of. A 0.025" ribbon cable is a pretty fine pitch. I used a vise to attach some IDC connectors to one once and ended up misaligning them and connecting the wrong wires. Is it possible to use two 0.050" ribbon cables, one for the top row and one for the bottom row?

On Tuesday, April 1, 2014 3:07:39 PM UTC-7, Doug D. wrote:
On Monday, March 31, 2014 9:45:02 PM UTC-4, whit3rd wrote:

... The pitch of the WIRES is 0.025", the even
wires mate with a bottom-row and the odd ones with a top-row connector pin.

Thank you, that's what I was afraid of. A 0.025" ribbon cable is a pretty fine pitch. I used a vise to attach some IDC connectors to one once and ended up misaligning them and connecting the wrong wires. Is it possible to use two 0.050" ribbon cables, one for the top row and one for the bottom row?

I suspect not. Both SCSI cables and 80-wire parallel ATA cables use this
fine-pitch ribbon, so the problem has been around for a decade or two now.
It helps to have a stereo microscope (or at least a jeweler's loupe)
and a strong light. It also helps to buy prebuilt cables...

On Tuesday, April 1, 2014 6:32:47 PM UTC-4, whit3rd wrote:
On Tuesday, April 1, 2014 3:07:39 PM UTC-7, Doug D. wrote:

On Monday, March 31, 2014 9:45:02 PM UTC-4, whit3rd wrote:



... The pitch of the WIRES is 0.025", the even

wires mate with a bottom-row and the odd ones with a top-row connector pin.



Thank you, that's what I was afraid of. A 0.025" ribbon cable is a pretty fine pitch. I used a vise to attach some IDC connectors to one once and ended up misaligning them and connecting the wrong wires. Is it possible to use two 0.050" ribbon cables, one for the top row and one for the bottom row?



I suspect not. Both SCSI cables and 80-wire parallel ATA cables use this

fine-pitch ribbon, so the problem has been around for a decade or two now..

It helps to have a stereo microscope (or at least a jeweler's loupe)

and a strong light. It also helps to buy prebuilt cables...

That's getting pretty fine for me to work with. I might have to look at a larger connector that can accept a 0.050" pitch ribbon cable. Thanks very much for your help.
Doug

On Saturday, March 29, 2014 2:11:56 PM UTC-4, Doug D. wrote:
I was wondering if anyone could explain connector pitch vs flat cable pitch. 3M advertises their MDR series of connectors as being 0.050" pitch, which is the horizontal pitch between connector contacts. However, these Centronics style connectors have two rows (an upper and a lower row).



Their drawing shows that the spacing between IDC slots is 0.050", but I don't understand how an IDC connector with two rows of 0.050" pitch contacts (effective pitch of 0.025") can use a 0.050" pitch ribbon cable. Do MDR connectors take two 0.050" ribbon cables, on one top of another?



Thanks,

Doug