Electrical connectors - Page 1
Forum section: electronics / beginners

author: av8or1
author_rank: Newbie
timestamp: July 29, 2014, 07:32:39 pm
content: Hi-I am a software engineer by profession but have been working on an electronics project on the side, outside the scope of the day job, for about a year now. The final product is a hand-held diagnostic tool that receives analog input from pressure transducers. The input is routed to a custom-designed PCB, which then displays the results on an LCD on the front face of the enclosure. Pretty straightforward concept really. I have my custom PCB designed and working; much of the software is written and so I am closing in on finishing the project. The problem that I have been working on for some time now is in regard to electrical connectors. I'm simply not liking the options that I have found during research and Google searches. Being a fan of Dave's YouTube videos, I thought I would join the EEVblog forum and pose the question here. The hope being that more experienced electronics types might have some input based on their own experiences.In order to avoid a long post and yet to provide as much information as possible as stated in Dave's sticky post, allow me to summarize the three general categories of connectors in my project (or so it would seem to me). I'm open to all feedback, and I appreciate that, though I really need the most help with items 2 and 3.1) The first are the wire-to-board (w2b) connectors. These connectors are used to enable external wiring to interface with your custom PCB. I played around with w2b options for at least a couple of months. In the end I went with JST connectors because of their positive locking features and smaller spacing, which means less real estate used on your PCB. There are both positives and negatives to this design choice, the biggest of which are (a) product availability in the USA and (b) the cost of the crimpers for each JST connector series. On my agenda in the near term is to see if any of the Molex crimpers could work and do the job instead. TBD.2) The next connector category is what I call wire-to-enclosure, though there may be a more-correct name for it. Basically this is how electrical input from external sensors enters your enclosure. There appear to be two variants: (a) solid wire through a hole in the enclosure that you guard with some type of strain relief or (b) plug-n-play style connectors that are rigidly affixed to the enclosure and that allow for input cable separation from the enclosure. I chose to go with the latter. And this is one of the real problem areas for me at the moment. My input is only 3-wire, +5V, GND and transducer signal. And I need for this to be as small as possible. Currently the openings I have designed in the enclosure are circular and are located at the bottom of the enclosure. They are 1/4". However I am having difficulty finding 3-wire 1/4" connectors. I did find one through Allied, it was a circular connector, 3-pin DIN but it was bigger than 1/4". But its real problem is that it comes to you completely unassembled; therefore it would be a huge time sink during production to assemble each connector. Perhaps that is "just the way it is" and if so, then ok, but I was hoping for a connector that would be more assembly-time friendly. Maybe I'm asking for too much, dunno. So anyway that is one connector that I considered.I also considered some type of "squid connector" solution. It was smaller than 1/4" and so it was good WRT the size aspect of a connector solution, but quite frankly I just wasn't feeling good about its long term picture. It didn't seem like it would "hold up" well over time, that is to say that it didn't seem durable, tough or rugged. This device is an automotive application that will be used in a garage and stored in a toolbox somewhere (not actually installed on a vehicle, again, it is a diagnostic tool). Therefore it seems to me that all components that I use should be reasonably sturdy and durable. I have designed every other component with that in mind.And just in case you are wondering, the diameter of the holes in the current enclosure design are 1/4" simply to keep the overall depth of the enclosure to an absolute minimum, which is being done to maintain the notion of the device being in the hand-held category.Ok so that is connector category 2 and it's a real problem for me.3) However it's connector 3 that is the real bugger-bear. I have spent at least 6 months off-and-on mulling this one over, trying different options, researching, guessing, anything. I've considered DIN connectors, cannon plugs, automotive style connectors, computing style connectors and the list goes on. But nothing seems to work. Why a third connector? Good question. In essence, this third connector is simply a break in the electrical cable that exists between the enclosure and the transducer itself. The transducer will be used in cramped areas of the engine bay and screwed into place. Therefore it would be very awkward to install the transducer with a long cable extending between it and the enclosure. So the solution is to break the cable very close to the transducer with one end of the connector remaining connected to the transducer, screw the transducer into position and then finally connect the electrical cable that runs from the enclosure to the transducer via the other end of the connector. So basically the cabling design is this:enclosure -> enclosure connector -> cable -> transducer connector -> transducerWhere each connector of course has a male and female half. So what's the problem? Well it's the ability to connect the two ends of what we're calling the "transducer connector" together. Often times there will be limited space in the engine bay. Therefore the connector should be relatively small in size overall and you need the ability to connect the two ends together with correct polarity of course and have them lock into place to secure the connection, but with only one hand and without visual reference ("blind"). And it's this aspect of this connector that has given me absolute fits. Connect the two ends of a small-ish connector together with correct polarity with one hand and blind. Hmmmmmm....I found a possibility through Allied, but it was simply too large, didn't seem that good WRT ruggedness and durability and also had a fair amount of "assembly required." I have also considered a custom connector, but such a decision incurs additional cost versus a COTS solution, so I have been focusing more on the latter thus far.Anyway. I'll stop. Thank you for any and all feedback.

author: av8or1
author_rank: Newbie
timestamp: July 29, 2014, 08:17:45 pm
content: Hi-Sorry for the additional post. However I forgot to mention the latest contender for the enclosure connector. The basic idea is to use the old VGA style connector, with the female end mounted inside the enclosure and the male end would connect to that, with the two screws on either end providing the secure connection. The most prominent example being the standard computer monitor connector. Only in my case there would be more pins, so the connector would be larger.I will offer differing numbers of transducers that can be used for simultaneous data capture (or singular, as desired), so the idea is to supply a male end connector that is designed to suit the user's needs. This style of connector seems rugged, durable and solid. Therefore it has my attention at this point.Still at the drawing board WRT the transducer connector however. Nothing has my attention at this point, unfortunately.Thanks again.