Best low voltage connector (12 v, 4 W DC PWM)

[WizardOfBoz]

All,

I have a Dell workstation. A T7910, with dual Xeon processors. Probably about a 6 yo design, but it works. I put pretty spifffy CPUs (E5-2699a - 22 cores each) in the thing and to get something that generates the same benchmarks I'd have to spend about $18000. I run computer models of diseases on the thing. Clinical trials of hundreds of different "virtual patients", spanning trial lengths of years sometimes. For those of a math bent, ODE models with 20-350 state variables, hundres of parameters. CPU intensive: I need the speed.

The Dell design is pretty bombproof, except that since I put in the more powerful CPUs, thermal management is an issue. An extremely poor design choice was made in the design: the CPU coolers (heat pipes with integral fans) blow air parallel to the motherboard. That's not a problem per se, but the exhaust from one CPU goes directly into the intake for the other CPU!. Dell had a solution back in the day: All-In-One (AIO) water-cooled units that blew air away from (perpendicular to) the mobo. To do that I'd need two of those coolers (hard to find, expensive, old and perhaps at end of service life) AND a special cover for my case which is also hard to find and expensive (e.g $116 on ebay). So I could get a questionably reliably system for about $500.

Instead, I bought two large (dual 140mm fan) AIO coolers (Arctic Liquid Freezer II), one unit per each of the two CPUs and will mount them externally. See drawing below.

This brings me to my question. I'm going to have to cut the two tubes for each unit. In the sheathing around one tube runs the wires that power the fans. A 4 conductor flat cable. I'm going to have to put an extension in, and I want to have something that is quick-connect. I had wanted to avoid soldering.

I seem to recall asking this before, but perhaps with less background. I need two connectors. For the quick connect I'm thinking of using a telco RJ-11. Better ideas?

I also need to splice the ribbon connector in at least one place. I was hoping to find a friction connector like one sees in some telco terminal panels. You lay the wires on metal forks in the connector and push down on the cover and the connection is made. Though I can't find any online, so if you know what these are called...

 

[Strostkovy]

For ribbon cables you are looking for Insulation Displacement Connectors (IDC).

Use whatever connector you want, but pay for a name brand version.

 

[EPAIII]

12V and 4W means about 333 mA of current. That is not very much so most insulation displacement connectors should be able to handle it. I would use double conductors for it, four in all, if possible. That would provide insurance against any of a number of things that can go wrong.

As for which insulation displacement connectors, first the RJ-11s were designed for phone lines, not power connections. They also were not designed for ribbon cable. So I would avoid them.

https://www.mouser.com/c/connectors/headers-wire-housings/?q=ribbon%20cable%20connectors

That is a long list, but most of the insulation displacement connectors for ribbon cable on it can be assembled with a bench vise or an inexpensive tool. If you choose two female connectors they can be connected with header pins but that does not provide any polarity protection. A five pin arrangement with one hole blocked (not the middle one - #2 or #4 would be best) and the corresponding pin on the pin header cut off can give you that polarity ID.

https://www.mouser.com/c/connectors/headers-wire-housings/?q=pin%20header&number%20of%20positions=5%20Position&pitch=2.54%20mm

I selected 0.1" (2.54mm) pitch components because they are the most common and that is probably what will match your ribbon cable, but MANY other pitches are available. So check your ribbon cable first. And be aware that most often you need a two row connector for most ribbon cable pitches.

 

[technocrat]

RJ11's are 150v at 1.5A max. Telephone lines are designed to provide current, your telco is a giant DC power station which is very expensive to run. This is why they all want to ditch land lines. RJ11 is a reasonable choice for your application, my biggest worry would be if using solid cable, any nick in the copper can fatigue and break later on, usually at a very inconvenient time. If you are using stranded, then you need a different RJ11 connector than the one for solid.

 

[EPAIII]

1.5 A max? OK, perhaps the ones that the telephone companies use are rated for that. But are all of them? RJ11s are a consumer, commodity item. Millions and millions are sold. With all the people out there selling the lowest cost product, at the very least I would want to see the data sheet first.

If you buy from a place like AliExpress, they probably won't even have a data sheet.

And I believe that the RJ11s are made for 26 AWG stranded wire which is almost universally used for phone cords. They use an insulation displacement connection which is specific to that wire gauge. If your ribbon cable is another wire gauge, then there can be problems.

RJ11's are 150v at 1.5A max. Telephone lines are designed to provide current, your telco is a giant DC power station which is very expensive to run. This is why they all want to ditch land lines. RJ11 is a reasonable choice for your application, my biggest worry would be if using solid cable, any nick in the copper can fatigue and break later on, usually at a very inconvenient time. If you are using stranded, then you need a different RJ11 connector than the one for solid.

 

[Strostkovy]

RJ11's are 150v at 1.5A max. Telephone lines are designed to provide current, your telco is a giant DC power station which is very expensive to run. This is why they all want to ditch land lines. RJ11 is a reasonable choice for your application, my biggest worry would be if using solid cable, any nick in the copper can fatigue and break later on, usually at a very inconvenient time. If you are using stranded, then you need a different RJ11 connector than the one for solid.

I absolutely do not trust those connectors to anywhere near 1.5 amps. RJ11 and RJ45 are also very susceptible to vibration in my experience.