Cursed connectors, why is there no middle ground option?

RE: Cursed connectors, why is there no middle ground option?

shabaz — Wed, 24 May 2023 17:52:38 GMT

I found a decent manufacturer M12 and a cheap M12, and took some photos.

First off, here are photos of the cheap version. This is the mating end view:

The other end of the connectors. This particular model looks like it will accept cable up to 5mm through the gland, but maybe up to 6 mm with the gland more splayed out.

These are the screw terminals inside the connector body:

Here's a decent manufacturer one, from Farnell I think, but I can't find the product code. This wasn't OTT-expensive, it was probably about 5-8 GBP. I don't know which manufacturer this is. I've done a search in my order history e-mails but I can't find the code since the text M12 is so generic.

Wire end of the same decent connectors:

With the screw removed, the socket terminals can be pulled out, and the left one is from the cheap version. It is more poorly machined from the outside. However I'm actually surprised that it's pretty good overall. I was expecting it to be worse, perhaps without a split, but it seems to be manufactured with the correct cuts, just without whatever polishing operation the decent manufacturer one has. It's brass I think, and no plating. I don't know what that means for corrosion.

The fit is very snug. I think it's a good electrical connection, at least with a newish connector such as this one (this connector is at least a couple of years old).

In summary, the cheap connector is not bad, it's better than I originally thought. However obviously for critical stuff, a decent manufacturer version should be used.

RE: Cursed connectors, why is there no middle ground option?

dougw — Wed, 24 May 2023 15:59:33 GMT

I like AMP plastic CPC (circular power connectors) for cost.

[embed:ad4490ac-0ce8-4f2d-a04c-9285646d5689:2716de2e-7734-45fe-8b42-7d87e8a61f0c:text=&style=link&farnell=592882&newark=&cpc=&avnetemea=&avnetema=&avnetasia=&comoverride=&cmpoverride=&AreaInteracted=rte-content&bom=]

RE: Cursed connectors, why is there no middle ground option?

shabaz — Wed, 24 May 2023 14:35:31 GMT

As another option, avoiding drilling holes, could be to replace one side of the enclosure (or a portion of the enclosure) with a PCB.

This style of D-sub looks very good, it is PCB mount, and would allow you to eliminate all wiring inside the enclosure, since you could just route PCB traces to whatever internal connector you wish to use. D-sub is robust enough for industrial equipment, provided it's not in an area that will vibrate much, and with paralleled pins I believe it can handle the current you likely expect (I'm guessing you're controlling stepper motors?). Also, this will still fully seal the inside of the enclosure from dust, since only solderable holes are drilled.

If you go down a PCB panel route, then there are other options too, for instance other shaped panel mount connectors, or using aluminium PCB services for complex cut-outs.

However for low-cost circular connectors, even the cheap aliexpress M12 will be better than the other 'aviation' connectors. I might have one or two of the Aliexpress ones, I can take a close-up photo of them if you require.

RE: Cursed connectors, why is there no middle ground option?

dougw — Wed, 24 May 2023 14:11:02 GMT

For high current, I like pluggable terminal blocks, they are so much easier to wire up, rewire and maintain. You might also check automotive connectors for low cost, high current.

RE: Cursed connectors, why is there no middle ground option?

shabaz — Wed, 24 May 2023 13:28:09 GMT

Hi Clem,

The connectors in your photo remind me of the ones that used to be on consumer CB radio gear, they are not good quality as you say.

The decent connector is M12 (there's also a smaller version, but M12 is a good size), it's used in industrial equipment, and I've seen it in railway gear, so it's trusted, and it's not expensive considering what it does, but definitely won't be anywhere near the price of the consumer CB style connectors (which of course just have the aviation name but are not really used in aviation).

There are cheap M12 connectors on ebay/aliexpress as shown in the photo below, however they are not 100% perfect, they are a tighter fit if you try to mate the cheap clone with the decent known manufacturer versions. When both the plug and socket are from decent manufacturers, the fit is smooth. They are still miles better than the CB style connectors.

Even cheaper could be D-sub style connectors, they may support the current you require (perhaps with using 2 pins per connection), and they have a small amount of protection and have screw fitting to prevent disconnection. It could be protected from dust by having all the cables enter an area through a separate area, through a bend (for instance) and then plugged and screwed in. I think it's a great option personally, but required drilling of non-circular holes usually!

Cheaper than that too could be Molex Mini-Fit Jr, however that would need a crimp tool, and would need some dust prevention techniques such as the separated wire entry point as mentioned above.