Connector so cable can be changed? - Page 1
Forum section: electronics / projects

author: ToBeFrank
author_rank: Regular Contributor
timestamp: August 10, 2011, 07:13:10 am
content: In my project I have two different buses I will interface to. Only one will be active at a time, and the connector to each bus is different. I'd like to create one board and have two different cables that can be swapped out. One cable has 3 wires and the other has 4, and they have vcc and gnd in common. That leaves me with at least a 5 pin connector, which needs to be reasonably small and locking. Anyone have any suggestions on what a good connector would be? I've looked on digikey, but the number of connectors is just overwhelming so I don't even know where to start.

author: ejeffrey
author_rank: Super Contributor
timestamp: August 10, 2011, 08:48:49 am
content: dsub 9 is not particularly small by modern standards, but it is cheap, rugged, has lock screws, enough pins, and is easily available in PCB mount. Modular telephone jacks (RJ11, RJ45) are less rugged, generally only support unshielded cables, and their latching is fairly weak, but they are super cheap.M12 circular connectors are smallish, a lot more rugged and not terribly expensive. The M8 connectors i think are only available in up to 4 pin.LEMO and Fischer make locking circular connectors that are relatively small and very rugged, but be prepared to spend an entire day trying to figure out what you want and making sure that the parts you order will actually mate. Then you will pay upwards of $30 for a mated pair for the privilege of waiting 12 weeks for them to be delivered.

author: ciccio
author_rank: Frequent Contributor
timestamp: August 10, 2011, 09:29:54 am
content: I second ejeffrey's suggestion for a DSUB 9, but there other option, cheaper than Lemo or Fischer..If you need a very robust connector, look at the XLR type, used in audio and lighting applications.They are available from 3 to 7 pins, from many manufaturers.Neutrik is one:http://www.neutrik.com/fl/en/audio/productline.aspxThey manufacture also an improved RJ type connector, that I've used successfully in live shows:http://www.neutrik.com/fl/en/dataconnectors/productline.aspxThey survived the abuses of a 120 shows in 80 towns tour..Another option could be a round type DIN connector, such the screw-on type made by Lumberg:http://www.lumberg.com/main/search_iframe.asp?lang=eng.I the above page you can find also the circular, screw-on connectors (IEC 60130-9) used in industrial sensors.For what I see, DigiKey does not stock neither Neutrik and Lumberg, but there are other manufacturer..ToBeFrank, you are not alone in having troubles sorting what you need from the big catalogs: I always look at the printed copy, where I can see better than on the on-line version.

author: metalphreak
author_rank: Frequent Contributor
timestamp: August 10, 2011, 01:04:27 pm
content: What are the requirements for the cable? In most cases a simple IDC/IDT ribbon cable works well enough. You can crimp the cables quickly and easily yourself, and all you need are rows of pin headers on the PCB.http://en.wikipedia.org/wiki/Insulation-displacement_connectorIf you need longer cables, Isecondthird the use of VGA/DSUB9 connectors. You can get the cables incredibly cheap (I have a box of 40 somewhere...)

author: ToBeFrank
author_rank: Regular Contributor
timestamp: August 10, 2011, 03:39:09 pm
content: Thanks guys. DSUB9 is what I'm switching away from because of size (the prototype uses it). It is way too big, both for the pcb/enclosure and the connector on the cable. The pcb is being designed to fit in an enclosure that is 3.15x1.58x0.59. The cable is connecting to the bus on a vehicle where the vcc wire is the 12V from the vehicle. I consume less than 350mA from that so it won't be carrying a lot of current. I was really hoping to find a connector where I could have cables pre-made and simply ship the design with the cable that's needed for the particular vehicle.

author: Frangible
author_rank: Regular Contributor
timestamp: August 10, 2011, 03:57:36 pm
content: Quote from: ejeffrey on August 10, 2011, 08:48:49 amLEMOs are expensive and long-lead items - but when you finally get one, it's a pleasure to behold and use. Tektronix used them on a bunch of test equipment, and after 30 some years of constant use, they are still serviceable. I've specified them for satellite GSE where the Canon circular connectors were just too big.

author: ejeffrey
author_rank: Super Contributor
timestamp: August 10, 2011, 09:17:35 pm
content: Quote from: ToBeFrank on August 10, 2011, 03:39:09 pmThe problem is that you specified latching. Small and latching are a relatively uncommon combination. For instance, DIN is often latching, but mini-DIN not.Micro-d is smaller than dsub. Normally it is used for higher pin count formats, but it is available in 9 pin. The 9 pin micro-d connectors I have seen don't have lock screws, but it should be an option.

author: ToBeFrank
author_rank: Regular Contributor
timestamp: August 10, 2011, 09:22:10 pm
content: Quote from: ejeffrey on August 10, 2011, 09:17:35 pmThat's good information, I didn't know that. I figured I would need latching because of vibration, etc. and I don't want the cable to pull out. Would friction connectors be enough to keep the cable attached?