GPIB Connector Question - Page 1
Forum section: electronics / testgear

author: SeoulBigChris
author_rank: Regular Contributor
timestamp: July 18, 2021, 09:51:50 pm
content: This is a stupid question, but I couldn’t figure it out after spot-checking a few Tyco data sheets.They sell GPIB connectors for installation on IDC ribbon cable. I was about to purchase a few of them to experiment with (my working theory is the ribbon cable based GPIB connections will be suitable for casual use, easier to handle, and cheaper than traditional GPIB cables).But I realized that these connectors have a 0.085 inch pitch. Can I assume that the IDC connectors in this family spread those out for use with 0.050 pitch standard ribbon cable? Or is one expected to buy special ribbon cable when using IDC Centronics connectors? I’m almost certain they use standard ribbon cable, but wanted to confirm with someone before ordering $50 of connectors.

author: TimFox
author_rank: Super Contributor
timestamp: July 18, 2021, 10:24:24 pm
content: I believe that the clunky “micro ribbon” connectors (referring to the mating surfaces, not the cable) are available internally configured for IDC to a 0.050" pitch flat cable, but read the data sheet. The flat cable is wider than the connector pattern. Ribbon cable at 0.050 in pitch is normally terminated with 0.100" pitch two-row connectors, or staggered pins in DB connectors.(I remember the full-size ribbon connectors, with something like 0.2 in pitch, that Tektronix used on their vacuum-tube CRO plugins, that were also available for soldered cable connections.)

author: SeoulBigChris
author_rank: Regular Contributor
timestamp: July 19, 2021, 09:00:05 pm
content: Well, that’s my guess as well. And considering I’ve never seen ribbon cable other than 0.050 and 0.100 spacing, I’m going to take the plunge and risk it.

author: cruff
author_rank: Regular Contributor
timestamp: July 20, 2021, 12:09:12 am
content: Digikey has 14 or so different conductor pitches listed in their search table, but none match 0.085" pitch. I don't know how common most of those are.

author: oPossum
author_rank: Super Contributor
timestamp: July 20, 2021, 12:53:24 am
content: Datasheet showing 0.050" spacing for IDC.https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=554103&DocType=Customer+Drawing&DocLang=EnglishNote that some IDC connectors are not for ribbon cable! Make sure you get the right kind.Digikey has a Champ 0.085 category. See attached.

author: pigrew
author_rank: Frequent Contributor
timestamp: July 20, 2021, 01:40:36 am
content: The drawing of the TE 553598-1 connector has notes describing the termination.It states the terminating side has two rows of 0.100" pitch, so an effective pitch of 0.050" for the ribbon cable.I'd assume that other models will also need 0.050" pitch cables.In a "real" GPIB cable, there are 12 twisted pairs, with a screen. Using ribbon cables should be OK for short cables but I'd start to worry if it became long.Premium cables have the pairs of data wires within an inner shield, surrounded by the control lines, surrounded by a second shield,as shown on this NI webpage

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 20, 2021, 05:14:49 am
content: Shielding concerns are real, but there are mitigations. Don't know any current part numbers but twisted pair IDC cable used to be available. It wasn't perfect, having five to ten centimeters flat straight cable, with pairs twisted one half turn between each straight section. Should extend the usable length a bit, but each application will be different and you won't know until you try.Premium cables have excellent shielding, but just looked up one on mouser - (ready made cable with connectors on both ends) 995 USD. At that price taking a chance on shielding sounds attractive.

author: BradC
author_rank: Super Contributor
timestamp: July 20, 2021, 05:30:57 am
content: Quote from: SeoulBigChris on July 18, 2021, 09:51:50 pmFrom my experience, unless you are using something pretty damn fast to drive the bus, ribbon will be fine. I've been using a meter of ribbon with 2 GPIB connectors on one end and the controller on the other for years at > 200k/transfers sec. If you were using an FPGA or a proper (not homebrewed) GPIB master then you might want something better.