Small coax connector advice please?
Discussion
Hello All,
I'm putting a set of proximity sensors on my car and have a problem to solve.
I've fitted the kit so the rear sensors are in and working. It's an 8-way setup so this takes care of sensors A to D. The wires for this are short enough to go to the control box in the boot so I can unplug them and remove the back bumper if need be. Here's the box. Sorry for the crummy phone pic......
Sensors E to H go in the front bumper. Their wires are very long so I need to put connectors in to get the wires through the bulkhead. The connectors will also permit me to remove the front bumper if necessary (I can park but many round here park by ear).
Here's a couple of the front sensors, with my grubby paw for scale...
Now for the question. The cables are coax but the OD is only 2.8mm. I found, on another job, that if tinned, the core wires will snap very easily. So, I need connectors that are crimp or screw on type. They'll go on the NS inner wing, well away from the muck and bullets behind the bumper.
I suspect the cables may really be for audio or even for inside a PC. I tried RS and the like but they wouldn't even tell me what I need to order. Perhaps they thought I'd say 'Boo' to them. So, I've heard of F connectors, RCA ones and God knows what else. Having not a clue, I could use a recommedation, maybe even a link or two.
Thanks!
I'm putting a set of proximity sensors on my car and have a problem to solve.
I've fitted the kit so the rear sensors are in and working. It's an 8-way setup so this takes care of sensors A to D. The wires for this are short enough to go to the control box in the boot so I can unplug them and remove the back bumper if need be. Here's the box. Sorry for the crummy phone pic......
Sensors E to H go in the front bumper. Their wires are very long so I need to put connectors in to get the wires through the bulkhead. The connectors will also permit me to remove the front bumper if necessary (I can park but many round here park by ear).
Here's a couple of the front sensors, with my grubby paw for scale...
Now for the question. The cables are coax but the OD is only 2.8mm. I found, on another job, that if tinned, the core wires will snap very easily. So, I need connectors that are crimp or screw on type. They'll go on the NS inner wing, well away from the muck and bullets behind the bumper.
I suspect the cables may really be for audio or even for inside a PC. I tried RS and the like but they wouldn't even tell me what I need to order. Perhaps they thought I'd say 'Boo' to them. So, I've heard of F connectors, RCA ones and God knows what else. Having not a clue, I could use a recommedation, maybe even a link or two.
Thanks!
From your description of the outer diameter of 2.8mm it sounds like you have an RG174-sized coax. That's marginally smaller than the standard plugs I carry.
Crimp is going to be easier to fit than compression or clamp type since the tool is easier to source.
You'll need a plug and socket solution, and given the movement then I would suggest BNC types. Have a look at the following
https://uk.rs-online.com/web/p/coaxial-connectors/...
and
https://uk.rs-online.com/web/p/coaxial-connectors/...
I have used this size and type but in 75 Ohm for attaching to some micro coax RGB leads so I know they work. I would still be tempted give the joints some protection from atmospheric moisture and also provide some additional support to handle vibration by wrapping each joint with a couple of layers of self amalgamating tape. It's what I use for weatherproofing outdoor cable joints. See link https://uk.rs-online.com/web/c/adhesives-sealants-....
A smear of silicon grease on the bare metal parts wouldn't hurt either. It won't stop conduction (a good thing) but will provide some additional corrosion resistance and so benefit long-term reliability (an even better thing) https://uk.rs-online.com/web/p/greases/0494124
Crimp is going to be easier to fit than compression or clamp type since the tool is easier to source.
You'll need a plug and socket solution, and given the movement then I would suggest BNC types. Have a look at the following
https://uk.rs-online.com/web/p/coaxial-connectors/...
and
https://uk.rs-online.com/web/p/coaxial-connectors/...
I have used this size and type but in 75 Ohm for attaching to some micro coax RGB leads so I know they work. I would still be tempted give the joints some protection from atmospheric moisture and also provide some additional support to handle vibration by wrapping each joint with a couple of layers of self amalgamating tape. It's what I use for weatherproofing outdoor cable joints. See link https://uk.rs-online.com/web/c/adhesives-sealants-....
A smear of silicon grease on the bare metal parts wouldn't hurt either. It won't stop conduction (a good thing) but will provide some additional corrosion resistance and so benefit long-term reliability (an even better thing) https://uk.rs-online.com/web/p/greases/0494124
Lucid gives some good advice and probably will fit the bill for your application. BNC connectors have a bayonet style connection which is easy to connect/disconnect but not the best electrical or environmental performance. Self amalgamating tape over the connection and all the way back over the crimps is essential to keep out any moisture.
If you are looking for something with a threaded connector, go for RG174 SMA or even SSMA m/f interfaces to create a less bulky and better electrical solution. You can get them in solder or crimp versions.
My 30 years experience is in the area of high frequency RF so I probably will tend towards overkill when it comes to interconnects. If you need any further advice, please ask but I think Lucid has pointed you in the right direction if you can live with the size of the BNC connectors.
If you are looking for something with a threaded connector, go for RG174 SMA or even SSMA m/f interfaces to create a less bulky and better electrical solution. You can get them in solder or crimp versions.
My 30 years experience is in the area of high frequency RF so I probably will tend towards overkill when it comes to interconnects. If you need any further advice, please ask but I think Lucid has pointed you in the right direction if you can live with the size of the BNC connectors.
Outstanding, gentlemen, thank you very much.
I'd already sussed from a bit of browsing that the cable size is RG174. What I need is straight male and female connectors x4 to make the joints. I'm experienced with solder and it seems to me that some conns, with a solder window, only need the conductive core soldering so perhaps the shielding just pushes in.
Re the environment, the underbonnet area shouldn't be too demanding. Encasing the joints in something makes sense and I don't expect to have to disconnect them often. I can also tack the wires down with tiny cable ties but in the past, someone suggested using blobs from a hot glue gun for this.
Having read, marked learned and inwardly digested your advice, I'll get on the case. Thanks again.
I'd already sussed from a bit of browsing that the cable size is RG174. What I need is straight male and female connectors x4 to make the joints. I'm experienced with solder and it seems to me that some conns, with a solder window, only need the conductive core soldering so perhaps the shielding just pushes in.
Re the environment, the underbonnet area shouldn't be too demanding. Encasing the joints in something makes sense and I don't expect to have to disconnect them often. I can also tack the wires down with tiny cable ties but in the past, someone suggested using blobs from a hot glue gun for this.
Having read, marked learned and inwardly digested your advice, I'll get on the case. Thanks again.
Scaleybrat's suggestion of SSMA would produce the neatest connection. If you can find male and female versions from a single supplier at sensible prices than I'd go with that. The advice re silicone grease and self amalgamating tape still stands, though with the small diameter of SSMAs you might be able to use a 3:1 clear heat shrink tubing as an alternative to the tape.
Regarding fitting, as you've already sussed, lot of the crimp plugs use a solder window for the centre pin connection. It's important to know whether your sensor cable centre core is solid copper or copper-coated aluminium (CCA). The test is simple. Strip back and expose a couple of inches of core wire. Hold a half inch of the tip in the flame from a lighter. If it glows then it's copper. If it crumbles and burns then it's aluminium.
Copper conducts the heat, and so it will solder without failing so long as it wasn't scored and weakened when the centre insulation (dielectric) was stripped off. Aluminium is a poorer heat conductor and a bugger to try to solder. You even have to be careful with crimping it. I once turned up to a job to install a projector and terminate the house network connections. The spark was a bozo who had bought and installed CCA network cable probably because it was cheap. What he 'saved' on the job the customer ended up paying extra in my labour costs for all the additional time wasted on broken connections.
Fingers crossed you're just dealing with copper. But if it is aluminium then look for crimp centre pin connections on the plugs.
Regarding the shield braid, that drapes over the centre tube so that it's trapped between that and the crimp collar. It provides the physical strength of the plug-to-cable union.
Regarding fitting, as you've already sussed, lot of the crimp plugs use a solder window for the centre pin connection. It's important to know whether your sensor cable centre core is solid copper or copper-coated aluminium (CCA). The test is simple. Strip back and expose a couple of inches of core wire. Hold a half inch of the tip in the flame from a lighter. If it glows then it's copper. If it crumbles and burns then it's aluminium.
Copper conducts the heat, and so it will solder without failing so long as it wasn't scored and weakened when the centre insulation (dielectric) was stripped off. Aluminium is a poorer heat conductor and a bugger to try to solder. You even have to be careful with crimping it. I once turned up to a job to install a projector and terminate the house network connections. The spark was a bozo who had bought and installed CCA network cable probably because it was cheap. What he 'saved' on the job the customer ended up paying extra in my labour costs for all the additional time wasted on broken connections.
Fingers crossed you're just dealing with copper. But if it is aluminium then look for crimp centre pin connections on the plugs.
Regarding the shield braid, that drapes over the centre tube so that it's trapped between that and the crimp collar. It provides the physical strength of the plug-to-cable union.
Thanks again Lucid_AV,
The centre core on the kit I fixed (another one from China) was silver in colour and I could solder this well enough but this made it very fragile. I used some lightweight copper cored wire, soldered it to both core and braid, arranged it with a 180 degree loop in each piece, added heatshrink and soldered the free ends together. I then insulated to soldered joints with heatshrink and bound the whole with tape. this way, there was no strain at all on the core-to-wire joins and everything was supported by the insulation. Three months on, it's still working.
The good news is that for this job, I can cut the cables and feed them through to the engine bay before buying the connectors. In the end analysis, sensors E to H must be connected to the right terminals on the control box. Colour coding at the new connectors will solve this one.
The centre core on the kit I fixed (another one from China) was silver in colour and I could solder this well enough but this made it very fragile. I used some lightweight copper cored wire, soldered it to both core and braid, arranged it with a 180 degree loop in each piece, added heatshrink and soldered the free ends together. I then insulated to soldered joints with heatshrink and bound the whole with tape. this way, there was no strain at all on the core-to-wire joins and everything was supported by the insulation. Three months on, it's still working.
The good news is that for this job, I can cut the cables and feed them through to the engine bay before buying the connectors. In the end analysis, sensors E to H must be connected to the right terminals on the control box. Colour coding at the new connectors will solve this one.
I had a look for easily available crimp SSMA connectors but they appear to be like hen’s teeth. In their absence, I’d use SMA instead. These appear to be OK quality and UK supplied.
https://www.wifi-antennas.co.uk/cable-crimps-and-c...
Good luck!
https://www.wifi-antennas.co.uk/cable-crimps-and-c...
Good luck!
I've just ordered 2 x 4 packs of M&F SMA connectors from Scaleybrat's suggested site. Just over a tenner all in.
Not so much a separate question now, more of an adjunct in the cause of clarification. I took a test piece of the reverse sensor cable, stripped it and tried soldering it. It is very thin (RG174) and the centre core wire is very fine gauge indeed. Thing is, the centre core wire is a shiny silver colour. It isn't attracted to a magnet. I was able to tin it using resin multicore solder so what is it made of? Yours, curious.
Not so much a separate question now, more of an adjunct in the cause of clarification. I took a test piece of the reverse sensor cable, stripped it and tried soldering it. It is very thin (RG174) and the centre core wire is very fine gauge indeed. Thing is, the centre core wire is a shiny silver colour. It isn't attracted to a magnet. I was able to tin it using resin multicore solder so what is it made of? Yours, curious.
Trenchard said:
It is very thin (RG174) and the centre core wire is very fine gauge indeed. Thing is, the centre core wire is a shiny silver colour. It isn't attracted to a magnet. I was able to tin it using resin multicore solder so what is it made of? Yours, curious.
Lucid_AV said:
It's important to know whether your sensor cable centre core is solid copper or copper-coated aluminium (CCA). The test is simple. Strip back and expose a couple of inches of core wire. Hold a half inch of the tip in the flame from a lighter. If it glows then it's copper. If it crumbles and burns then it's aluminium.
To add to what I wrote in a previous reply, you could have copper with a coating of tin. It helps with soldering. Which ever though; naked flame - glows = copper. Naked flame - crumbles = aluminiumTrenchard said:
<snip>
Re the environment, the underbonnet area shouldn't be too demanding.
Automotive engine compartment electronics are rated -40 - +125°C. Also have to withstand varied liquid (and sometimes gaseous) unpleasantness. Connectors are almost always a weak point. Anything you can do to choose good quality, protection and support then do it Re the environment, the underbonnet area shouldn't be too demanding.
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