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I have gotten a hold on a really great deal on Connectors for a electrical project of mine. These connectors come in various sizes, but common for them all is that they are rated between 250 volts to 400 volts. My system is using 12V and 5V.

The project is to connect a bunch of LED lights together in my garden on various distances. I am aware of current drop in the wires; I am just not sure what kind of issues I can encounter from these connectors.

So, can I use these connectors and what could the side effects be?

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  • \$\begingroup\$ Some information on the connectors, or pictures of them, might allow someone to make a useful comment. \$\endgroup\$ – Peter Bennett May 4 '16 at 22:31
  • \$\begingroup\$ Side effects might be using way too much space for the job. \$\endgroup\$ – Barleyman May 4 '16 at 22:58
  • \$\begingroup\$ It's like how a car can go at 150km/h but it'll still be fine at 10. Anything under the maximum ratings is fine. \$\endgroup\$ – Sam May 5 '16 at 1:30
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Connectors are typically rated with a maximum voltage, meaning every voltage up to the rated one is okay. For you that means the 12V and 5V are totally fine to be used on a 250V connector. You still need to make sure you don't overload them with the current you are going to use, e.g. a 5A/250V connector should not exceed 5A, even if you use it only with 5V.

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  • \$\begingroup\$ I'm still getting into the Amp vs Volt domain but I thought 5A at 250V acted differently than 5A at 21V/5V? \$\endgroup\$ – evilfish May 6 '16 at 6:18
  • \$\begingroup\$ that is right, but in a connector there is not much you need to have an eye on. Main concern is how hot the connector is getting (thats what the amp rating is for) and the dielectric strength, material and space between the contacts (creepage distance) and so on... if your currents get really small the wetting current might also be interesting, have a look at @andy-aka s answer for that. For a hobby project, choosing a connector should not be too hard here and you can basically just use whatever you can find. \$\endgroup\$ – arne May 6 '16 at 21:19
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Wires and cables as well as connectors work the same way. They have voltage, and current, ratings which are maximum ratings. It is always OK to use less voltage or less current than the rated maximum.

  • The maximum voltage of a wire or insulated connector is determined by the insulation. A higher voltage means the insulation will be thicker or made of better materials. A multi-contact connector might also have larger distances between contacts to prevent arcing.

  • The maximum current of a wire or connector is determined by the conductor thickness and contact area — which determines the resistance, and therefore the amount of heat produced. A wire or contact which has less resistance, or can tolerate higher temperatures without being damaged, (or is in an environment with better cooling) can handle more current.

Therefore, the only consequence of using an over-rated connector is that it will be larger than necessary. If they're not too large for your application, then don't worry about it.

(Another way being too large could affect things is in the particular case of crimped joints: attempting to crimp a large crimp barrel onto a small wire will make a poor joint likely to fall apart. They should only be used for the wire sizes specified.)

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Those are typically MAXIMUM ratings, and frequently they are actually called "Maximum Voltage" or whatever. For all practical purposes, there is no danger in using a component at below its maximum rating.

Note that the maximum voltage rating and the maximum current rating are independent. So even though you may be well below the max voltage rating, that doesn't mean you can exceed the max current rating.

Two possible disadvantages of using connectors rated for high voltage in a low-voltage application include:

  1. SIZE. Connectors rated for higher voltage may be physically larger than you need. This may be a problem in situations where you have a space constraint.
  2. CURRENT CAPACITY. Since Power is voltage multiplied by current, connectors rated for higher voltage may not have the current rating you need for a lower voltage of equivalent overall power capacity. In most cases, you could parallel connector pins to increase current handling capacity.
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A good connector for power at 250V is not necessarily a good connector for signals at 10 uA. It all depends on how the two parts mate together - read up on wetting current - wiki says this: -

In electrical engineering, wetting current (sometimes also spelt as whetting current in archaic sources) is the minimum electric current needing to flow through a contact to break through the surface film resistance.



"Wetting current" should not be confused with the current needed to generate involuntary insanitary actions in a human.

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One possible risk is that of misconnections. If someone inadvertantly connects mains voltage to an ELV circuit by plugging together two devices that were never intended to be plugged together then bad things can happen.

Unfortunately most high current connectors seem to be rated for mains voltage. So short of having custom connectors designed and built for your devices (which is only practical at large volume) it's difficult to completely eliminate this risk. However it is prudent to take steps to minimise it. You should take steps to understand what environment your device is likely to be used in and what connectors are commonly used for what purposes in that environment. Another option is to use connectors that support blocking some of the pin positions and block a random selection of pin positions to reduce the risk of misconnections.

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