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PowerPoles connecting togetherWhoever said “consistency is the hobgoblin of small minds” never tried to build anything. Or fly a plane, launch a rocket, collect data, write code, or test a hypothesis.

It’s easy enough to standardize the physical connectors in a project (e.g. build your whole robot with just one or two sizes of nut/bolt holding it together). But what about power and electrical connections? It’s obviously better in some places to have plug style connectors so you can swap out parts, reconfigure and so on without having to cut wires or heat up a soldering iron. And for consistency it’s best to use the same kinds of connectors throughout your project. But, most power connectors are molded onto a cable in a factory. The only way you can put one of these connectors on the end of a cable you already have is to buy a cable with that connector on it, then cut the connector off and splice it onto your cable.

Abuse of wire nuts

Don’t build kludgey connectors like this!

There’s a much cleaner solution called Powerpoles. You crimp the metal contacts onto the ends of your wires and slide them into colored plastic housings. Each housing is hemaphroditic: the resulting Powerpole can connect to any other Powerpole instead of ‘male’ and ‘female’ connectors that only connect to their opposite. Powerpoles were developed for the ham radio community, but they are useful for all sorts of applications. For my solar power/lighting/gadget business, I have standardized all my parts to connect with Powerpoles. The friendly, lego-looking, color-coded connectors make it easy for my customers to connect whatever parts they need, even if they know nothing about electricity. More tech-savvy customers can easily add Powerpoles to other 12V gadgets to connect, hack, and mod my products. The fact that anyone can put together cheap ($0.14 cents/contact, $0.39/housing) professional quality connectors at home, with minimal tools, has a decentralizing and democratizing effect.

The quick and dirty way

The quick and dirty way

The basics are pretty simple: crimp a contact onto the end of a wire. You will need a tool with good mechanical advantage, like channel-locks. Align the contact with the housing so the little lip at the end of the contact will go over the end of the flat spring in the housing. Slide it into the housing until you hear it click (meaning it’s properly seated on the spring in the housing), and use. The tongue and groove on the side of the housing means you can make multi-contact connectors with whatever configuration you need. Just make sure all of them are configured the same; for example I always slide the tongue on a positive housing into the groove on a negative. If you are just putting together a couple of Powerpoles, this may be enough.

But, if you are making a lot of them, using them in critical applications, or want to avoid trouble in the future, there are a few tricks to getting consistently good performance that I have learned by putting together thousands of them:

There is a relatively inexpensive ratcheting crimping tool called a TRIcrimp ($40) that will produce much better crimps than you can achieve with pliers/channel locks (and much easier; your tendons will thank you). Instead of squeezing the contact flat over the wire, it presses a groove into the top of the contact, thus reducing its diameter and pulling the contact tight around the wire.

Quicker and less Dirty

This ratcheting tool makes a neat easy crimp

If the strands of stranded wire are all parallel inside the contact, they can slide out no matter how well you crimp it. You can pull the contact off with finger strength. If instead you coil the strands into a spiral, there’s an irregular surface for the crimped contact to hold on to.

Straight vs. Spiral

Straight strands pull out easily. Spiralled strands do not.

If you are using thin wire, it’s going to be loose in the contact, and it will be hard to get a good crimp. If two diameters of wire will fit in the contact, strip twice as much wire and double it back. If four diameters will fit, strip four times as much wire and double it back twice.

A little extra work, a way better hold

Fold up wire as necessary to fill the contact

It takes a decent amount of force to push the contact into the housing so it clicks. The weakest point in any Powerpole assembly is the place where the contact meets the wire insulation. It will always bend there first. Not only can this be frustrating when you are trying to slide the contact into the housing, it’s also where the wire is likely to keep bending any time the connector is under stress. Eventually, it can snap through metal fatigue. And, Murphy’s law states that this will happen at the worst possible time. The solution is to use adhesive lined heatshrink (also called ‘double walled heatshrink’) to reinforce and armour over the joint. This is essentially a DIY equivalent to the strain relief on factory-made connectors. To ensure that the contact will still fit in the housing, you should use the smallest diameter heatshrink you can (for the 15 amp Powerpole contact, use 1/8 inch diameter heatshrink). If it’s a really tight fit, a tiny dab of any lubricant (even cooking oil) will work wonders.

heatshrink everything all the time

The joint is a weak point. Armour it with heatshrink.

You can ‘merge’ wires at powerpole connections. Two or more wires can go in the same contact if they are thin enough (strip back about twice the length of wire that will fit into the contact so there is room to heatshrink over and still fit it in the housing). This is handy if, for example you have several wires from a component that need to be connected to ground.

If two wires need to go the same place, why keep them seperate?

Merging two wires into one contact

You can also ‘fork’ wires using Powerpoles. Strip the insulation off a wire in the middle, double it back and insert into a contact, then also put a contact on the end of that same wire (much faster than soldering a 2:1 connection in the wire).

one wire, many connections

First strip insulation midwire, then fold and twist.

At this point, you may be thinking it would be simpler and faster to just solder the contact onto the end of the wire rather than going through the whole process outlined above. The thing about soldering though is that stranded wire can suck up that solder like a straw, turning an inch or two at the end solid. That turns the weak point where the contact meets the wire insulation into a solid piece, which makes it much more brittle and failure prone. Plus, you can twist, crimp, and heatshrink a dozen contacts in the time it would take just for your soldering iron to heat up.

Note: this article is being simultaneously published at http://www.yetisolar.com/blogs/news

Rustom Meyer

I have more projects than I know what to do with. I’ve previously made toys, ceramics, jewelry, clothes, solar ovens, a custom bicycle, and flashlights, as well as renovating an 150 year old house. My obsession for the last few years has been small solar lighting/power systems: (www.yetisolar.com).


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Comments

  1. Me says:

    The title got me excited to click. I thought it was going to be about actually making connectors, maybe 3d printing powerpoles or something similar to that.

    I usually buy powerpole stuff at hamfests or on Ebay. I don’t really like the prices I usually find. Sure, the price is no barrier to using them on a project or two here and there but I want to replace all my DC power connections throughout the house, cars and shop. Then I would like to fill a group of parts drawers with contacts and housings of all different colors so I can color-code different voltages. I like the way powerpole housings can be combined to make different shapes so I can make sure incompatible voltages have incompatible connectors without stocking a bunch of unique plugs.

    Anyway, the dollar a piece price I usually find connectors is a little on the high side for filling drawers. Much worse are other accessories such as powerpole splitters. Apparently when you wire a handful of powerpoles together and drown them in a gob of epoxy their value increases 10-fold.. Pretty much the same happens if you panel mount them. Go figure. Power connectors are exactly the sort of thing that I want to already have on hand though, not something I want to put a project on hold for while awaiting an order or the next hamfest. I had been thinking of switching to some sort of Molex connector but with their sexed pins and sockets and their housings permanently pre-defining the number and configuration of pins that is nowhere near as elegant.

    So… I was kind of dissapointed to see your article wasn’t about making connectors. But.. the Powerwerx link looks pretty good. I’ve seen them on devices but never encountered anyone selling powerpole PCB mount contacts before. Maybe I can build those splitters myself. This might work out afterall. :-)

    Thanks!

    1. Rustom Meyer says:

      Sorry to disappoint :(
      I suppose you could 3D print something like a Powerpole, but I don’t think it would work very well, as the slight surface irregularity/roughness of 3D printed objects would make them slide together poorly. Also, I don’t think you would save money, which was the original objective.
      Powerwerx is pretty much the cheapest place to buy them online (and way less than a dollar for a housing+contact; more like $0.50). I buy them in big batches of hundreds at a time, so I also get the volume discounts. I have them on hand (filing bags, I guess?) for projects and for making my solar lights, but I also only stock 8 color/size combinations.
      The crazy high prices of things like splitters is what encouraged me to create the techniques to fork and merge that I described above. Maybe being cheap is the mother of invention as much as necessity is :)

  2. Kevin Reeve says:

    I have been using Powerpoles for over 10 years and they are fantastic. Simple, genderless, and just work. Highly recommend them.

  3. I’ve used them before too. They are great. I love how you can gang several together into a multi-contact connector.