Better terminal blocks?

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fernfrost

Member
Joined 2015
#1
Standard terminal blocks tend to twist when tightened and I always worry about damaging the boards.

Are there better alternatives?


pcb-terminal-blocks.jpg
 
#3
I much prefer polarized plugable connectors to these screw down terminals. Once connected correctly and labeled, not a problem in the future. I use the Phoenix screw down terminal when first building, but always switch them out to something like Molex KK 2.54mm,Molex SPOX, etc., based on the requirements (voltage, current) of the circuit. Favorite recent terminal series is the TE Dynamic D5200 series. Of course for those, the board needs to be designed for them. The Molex SPOX are 5.08mm centers, so can usually just replace the normally used Phoenix connectors directly. Of course the crimp pins need a crimper of some sort, but normally not a problem.
 
#4
You get terminal blocks with pins on the ends that go through holes in the PCB, to transfer the stress to the board.

Twisting means you could be using too much force. Try larger rated terminals. Or a smaller screwdriver.
Use soldered connections to DIN channel terminal blocks, that is safer.
Similar devices are very common in industrial panels.
 
#5
Anyone with experience knows soldered connections are not the best way of connecting wiring to PCBs. To avoid the twisting you could use the minimum of a 3 pin version. It is mainly the 2 pin versions that twist. If you use for instance the 4 pin version you can have 2 x + and 2 x - in a power supply and have the benefit that it does not twist.

Of course one does not need to tighten the screws like tightening a cilinder head. If you worry about such things you could use the versions with M3 screws and crimp the O shaped AMP connectors. These are a good solution for amplifier outputs, power supply connections etc. as they can have some serious current. Even when the screw is not tightened right these will make good contact anyway. Quite reliable.

And... use branded stuff from the West, not iron/steel based cheap far east garbage. Phoenix makes good ones that rarely fail.

https://www.phoenixcontact.com/de-de/produkte/leiterplattenklemme-mkdsn-15-3-508-1729131
 
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#6
fernfrost said:
Standard terminal blocks tend to twist when tightened and I always worry about damaging the boards.

Are there better alternatives?


View attachment 1201827
Click to expand...
These are also available with a pair of small plastic pins at the bottom.
These would drop in small holes in the PCB and will prevent rotation when tightened.
But you have to look for them; Würth had them last time I looked.

Edit I see @NareshBrd made the same point.

Jan
 
#8
I noticed that it is the plastic that twists more than the conductor itself. Also, it happens more on cheap ones. As Paul said, if you are designing something yourself and have pcb space, use 3+ ones instead of two contact. Proper hole sizing is very important. I have tendency to hold the housing with fingers when tightening it down, works well (even when it doesn't twist, my mind thinks it reduces the chance of making cold joint).
 
#11
On my machine PLC, there are blocks which clamp down.
The wires coming from the machine are on a set of screw terminals (male).
The set is pushed into a set of terminals on the PCB, (female). Or maybe the main PCB / body.
The male block set is secured by screws to the female block set.
It is on two levels, one for positive, and one for negative for valves and temperature sensors, and maybe three for the proximity switches.
It was installed in 2018, needs little attention, so please forgive me if I am fuzzy on details.

So if I need to remove the PLC, I simply unscrew the end screws, and the top set comes off.
It is much easier this way when you have like 5 sets of wires, and more than 50 wires to deal with.

And you can do it the Japanese way, no terminals sets with same number of wires, less confusing to work on.
 
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