For some time I have "standardised" on my connectors for my small PCBs as the molex mini SPOX 2.5mm connectors.
They have a number of features that make them useful - higher density than screw connectors (unless tiny tiny screws), and being pluggable makes it possible to simply unplug one PCB and plug in a replacement. They need a crimp tool, and being molex it is not cheap, but they are easy enough to make up. Even with screw terminals I would always use bootlace ferrels, which makes this no more hassle really. The other advantage of plugs is you can crimp / wire the plug more easily away from where the plug has to connect to the board (which may be in a tight space), and then just plug in.
However, feedback from a customer of the alarm system is they do not like them - the main issue is the expensive crimp tool. They worked around by getting pre-crimped wires. But also it means I cannot sensibly ship a board of any sort with these that can just be used.
The alternative I am trying now is Phœnix Contact connectors (e.g. these).
- They are also 2.5mm spacing. This means existing boards can use these new connectors with no change. In practice they are a fraction longer so hang over the edge of the board very slightly, so the PCB is being changed to accommodate on next version, but that is not enough to be a problem on existing boards.
- They are slightly narrower which allows some boards with lots of connectors to save a few mm width.
- Like the mini SPOX, the 2.5mm spacing is close enough that one could fit 0.1" square pin headers instead if needed.
- The plugs are "push in" wire contacts, no crimps, meaning I can supply plugs with the boards and they can be used right away.
- Available with locating pegs, useful especially for smaller sockets, PCBs space permitting.
- Available in black or white, and surface mount, and right angle and straight, and socket on PCB or plug on PCB, which is really flexible.
- They are close enough spacing that the plugs can fit a standard 0.1" square pin header too.
Another small downside is the plugs are longer, which means at least one board (the keypad module) will stay as SPOX, but be supplied with a plug and crimped leads as they solder on to the back of the keypad. The other cases look like they will still work in the back of an exit button box, etc.
Finally, today, after a week of UPS being stupid, I have the first of these to play with. They are as expected.
One simple test was can a Phœnix Contact plug fit a SPOX socket, and the answer is, sort of, with a bit of force, not ideal, and it is the other way up so a plug made for Phœnix Contact will not just work in SPOX even if you force it as wired backwards.
Here we have the mini SPOX (white) and the Phœnix Contact (black). You can see what happens trying to plug on in to the other. And no, the SPOX don't even slightly fit in the Phœnix Contact socket.
The wires that work are a factor. The crimps on mini SPOX can handle a range of wires, stranded and solid. But these push in are a tad more picky. The first test was confirming that the really very nice heavy duty Belden 0.75 mm² black/red stranded wires just work. They are probably the biggest it would handle, but really nice for power wires.
The next test was that solid cat5/6 cable works, and yes, that seems a perfect fit for signal wires.
The one wire that does not work is a finer stranded wire - it does not have the solidity to push in to the plug. And, sadly, my smallest bootlace ferrules are also too big it seems. This could be a slight issue for some existing wiring as "alarm cable" is often the fine stranded wire, though solid cat5 cable seems to be more common now. That said, it may be that the same technique for removing wires (pin/screwdriver) could be used to lift the lever and allow the thinner stranded wires, albeit slightly more fiddly.
In case you are wondering how it works, they have very nice data sheets.
To remove the wire you need a pin, or, as in this case, a very small screwdriver.
The plugs will fit on 0.1" square pins if needed.