So I think I'm going to rewire my cnc and put in the limit

So I think I’m going to rewire my cnc and put in the limit switches I got. Currently the motors are just soldered to longer wire. I tried using Dupont connectors but I couldn’t do it well with my cheap crimpers and connections were loose or just didn’t work. Does anyone have preferred connections or terminal blocks?

Aviation plugs

I soldered screw terminal strips back to back and located them on the structure. I recommend using pin crimps or solder the wire.

I just soldered mine. But this reminds me that I still want to install end stop switches. Or maybe inductive sensors (I bought 6 a while ago).

These things are cool - they are called poke-home connectors, you just stick the wire in the hole and done. Works with stranded wire as well. Available at Digikey.
http://www.avx.com/products/connectors/wire-to-wire/reduced-thru-wire-connector-18-24-awg-9286-200/

@Darrell_n where do you get them?

@donkjr Digikey. 4 wire ones are a bit over $1
https://www.digikey.com/product-detail/en/avx-corporation/009286004203906/478-9845-ND/5995412

wow, those are nice. if you say they work well, i’ll have to try a few. i used one of these kits (but a different brand) http://www.hansenhobbies.com/products/connectors/connectorkits/ck_psck/

it took a lot of fidgeting to get them to work.

limit switches are on my list of things to do, but i might convert from belt to lead screw first…

Ohh I like those poke home. What rating do the have?

Go to the AVX website AS SHOWN ABOVE and look at the datasheet (Gray menu, rhs, top item).

http://www.avx.com/products/connectors/wire-to-wire/reduced-thru-wire-connector-18-24-awg-9286-200/

These can be inserted and REMOVED?
https://www.digikey.com/products/en?mpart=009286004021906&v=478

Yeah those ones have a little button to release the wire. They are a bit more expensive. The other ones you can apparently remove the wire by twisting it… I think they said it’s good for up to 4 or 5 insertions and removals, so you would be able to change out a motor without replacing it.

I found some really nice wire on Amazon, its 100 strand 20 ga with silicone insulation, so it’s really flexible. I think you would have to tin the ends to use these connectors because the strands are really soft and you might have a hard time inserting them. But, this wire works great for motor leads because it is low resistance and so flexible. They have several gages, colors, and roll sizes.

I think I am going to start using these poke-home connectors in all my builds because my motor supplier just changed all their motors to have just a short pigtail with a JST connector on it instead of the long leads like OB. It’s a real pain to crimp on the individual contacts to make up a mating connector, so these would be a lot faster and not much more expensive.

MG

@Darrell_n

I added some of these connectors to my Digikey cart to try them. Thanks for pointing us to them.

I am skeptical of connections that are not screwed down in CNC applications. Especially the push in style. I have experienced unpleasant intermittents even using screw terminals without tinning the leads. Our machines undergo a lot of vibration and noise is a key design factor for good electrical reliability.
I even solder ring tongue and faston connections rather then crimping to insure ground connections are not flakey or increasing in resistance.

-----------------------
Wow lots of silicon wire choices I did not notice on amazon. I like that wire so its now in my cart!
In the specs it says low impedance which makes me wonder if they mean resistance? Its not obvious to me why high strand count wire would have lower resistance (or inductance) than other lower strand count stranded wire of the same size?? Stranded wire has the equivalent cross section as solid for its AWG. This results in it sometimes being larger by a fraction of a strands diameter. Then again at about 500 strands the integral of one wire diameter would not seem to change the resistance much. In any case I doubt the difference in diameter between high and low strand count is relevant in my applications.
The main reason for high strand count is flexibility and for this reason I will likely use this when I rewire that which runs through a drag chain.

I still highly recommend twisting these wires into pairs, especially for end stops. In other applications (PWM) I twist a ground with the signal. I ended up using CAT5 (patch) cable as it is stranded, TP and good density. I do not seem to have the same noise problems others have reported and I am blaming that on full use of TP and lots of attention to signal isolation and grounding. I also do not run spindle drive through my drag chain. The driver is on the gantry next to the motor. Fingers crossed… knock on wood!

@donkjr Like you, I am a bit skeptical about the low impedence thing, it may have some effect at high frequencies with the skin effect, since there is a lot more surface area. It may also provide somewhat lower inductance, although I am not sure about that. However, the good part about this wire is the high temp silicone insulation, and the many small wires make it extremely flexible. Smaller wires may make it easier to fit more conductors in the same area with respect to overall diameter, larger wires would have more space in between and thus less actual copper for the same OD. Be interesting to compare the weight per foot between the small and large conductor wire.

With any wire in a high vibration industrial environment, I always use crimp on wire ferrules like these.

They keep the wires from fraying, and are much better than tinning the wires. They provide strain relief and a solid mate for screw terminal blocks and keep stray wires from shorting to adjacent terminals. They are also great for fitting small wires into crimp type ring and fork terminals, they are like a wire size adapter. You can put a very small wire into a crimp terminal without worrying about it coming loose. They also work great for putting stranded wire into the old style poke home connectors that arent made to work with stranded wire.

The crimpers are a bit pricey, but you can find reasonable ones on Amazon.

4898a224f7f4b341ddc77aa38cf2e6c1.jpeg

@Darrell_n
We are on the same page.
I also use these ring ferrules. But I solder them (anal I know). They are much better than tinning the wires but some times I get lazy!

Is the skin effect “in affect” when the multiple strands are touching and conductive??? :). Anyways not relevant to out application as you suggest.

@donkjr Soldering is sometimes counterproductive. Soldering a wire to a ferrule or terminal causes solder to wick up the strands to some point behind the physical connection. This causes a point where the wire transitions from essential a solid wire (spaces filled with solder) to a stranded one. This becomes a point of failure because the strands cannot slide against one another during flexing and so stretch the wire strands, causing metal fatigue. This will surely break the wire faster than if it was not soldered.

Bell ( The Telephone company) did a lot of research on this 50 years ago and determined that soldering these types of terminals caused failure earlier than if the wire was just crimped. They also determined that properly crimped connections formed a gas tight seal with at least most of the wire strands and this prevented corrosion in the joint.

From a white paper on the subject:

"A crimped spade terminal actually creates a metal-metal colloidal bond at the surface between the wire and the terminal, and if done right, no gas remains between the surfaces. This ensures longevity and safety, making this the preferred mechanism in industrial implementations. "

And:

“Definitely: a crimped connection will be best if properly done. One thing I have seen many times is that soldered connections create a critical point at the point where the solder ends on the side opposite to the terminal: the solder wicks between the individual wires of the cable, producing a very stiff zone where the cable’s flexibility is lost… this point is very fatigue prone, and will break if the cable is moved or flexed or subject to the slightest vibration. Soon, the rigid solder impregnated part of the cable breaks and separates from the rest of the flexible cable.”

I have seen this hundreds of times in industrial applications, and forbid our manufacturing department to solder any crimped connection. Failure rate for wire connections dropped to almost zero.

Oh, and “Skin Effect” only really applies to high frequencies. Doesn’t really apply at DC. And, the shorting of the wire surfaces together in the wire bundle doesn’t really change the skin effect. It is a phenomenon related to the diameter of the individual strands.

MG

@Darrell_n I know your correct and agree that soldering would be worse than a good crimp if it is flexing at the solder joint.

Alternatively I don’t use solder when the wire is going to undergo any movement within 6 inches or so. In fact I don’t let any wire flex at the connection. I insure that moving or vibrating wiring are mechanically fixed (tie wrapped etc.) long before any joint. Good practice no matter what your preference is :).
This insures that there is zero ohm and corrosion free electrical contact with the wire and with fracture protection.

I just don’t trust crimps…I know they are supposed to create gas tight connections but when they don’t the intermittents they create are a bugger to find. Especially true with logic levels where a volt matters.

Interesting discussion…

Got some samples from the AVX website, they were very accommodating.
Now for some tests…

99d21683044257573a34550f3b8966d1.jpeg

@Darrell_n I got the wire in fine and it holds really well. However I cannot get this “…twist pull wire extraction” to work.

Have you tried to pull these out :)?

Features & Benefits
Simple strip and poke-home wire insertion with twist and pull wire extraction

High spring force stainless steel contact maximizes cost, strength, and flexibility

Accepts 18-24 AWG solid and stranded wires

Expanded size offering to cover multiple power and signal applications: 1p-6p

http://www.avx.com/products/connectors/wire-to-wire/reduced-thru-wire-connector-18-24-awg-9286-200/

5debde1a2dd536a35d7d9154e2bfff0a.jpeg