From what I understand, when you hook up the Switching Power Supply 12v Dc 30a 360w to the wall outlet, you have to be very careful; careful not to get the wires mixed up; careful not to have anyone or anything touch the leads (in fact the first proper project I intend to print out will be a casing to fit around the switching power supply), or just order one from someone.

Now there are three wires that go into the US wall of particular concern, and these wires come out of a standard PC cable with the female end cut off, and they hook the power supply. Like the external casing, these three wires are also insulated, and when you take the insulation off the bare wires and connect it to the power supply, you have to use Electrical connectors of some sort to connect them to the power supply's screw leads.

I bought some electrical connectors just for this purpose, but I'm not entirely certain they will be good for this purpose, so I thought I'd check here first.

Picture of GE Electrical Connectors 50956, 40 piece set

There are specifications on the back:

╬                  ╬        AWG           ╬  Wire Size  ╬ Stud Size ╬
╬ Spade Terminals                                                   ╬
╬  YF1.25-35 (red) ╬        22-16         ╬   0.5-1.5   ╬    3.7    ╬
╬ Ring Terminals                                                    ╬
╬   YF1.25-4 (red) ╬        22-16         ╬    .5-1.5   ╬    4.3    ╬
╬ Butt Splice                                                       ╬
╬   BF-1.2SS (red) ╬        22-16         ╬    .5-1.5   ╬   n/a     ╬

Not sure if I should use ring or spade terminals, and I don't know what wire size to use; and I don't know what wire grade is inside a standard PC power cord or even if these are safe connectors to use for this.


2 Answers 2


It is okay to just use bare wires in the type of screw connector found on your power supply. They're designed for it; they have a little plate under the screw that prevents the wires from being frayed by the screw.

If you want neater wire termination, you should use one of the spade type ones. Pick the smallest size that fits your wires.

PC power cords are generally fitted with an IEC C13 plug, and those are rated for 10A (meaning also the wires themselves will be able to carry at least that much current). This is fine for any home 3D printer which usually draws a fraction of that.

  • 1
    $\begingroup$ Specifically, a power supply rated 30A at 12V, is therefore taking in a bit over 3A at 120V. Wire gauge 18 to 24 or so is fine (depending on air circulation, bundling, etc.). See [engineeringtoolbox.com/wire-gauges-d_419.html]. Wires on the 12V side should be heavier. $\endgroup$
    – TextGeek
    Commented Jan 17, 2016 at 23:01
  • $\begingroup$ @TextGeek thank you for the link! Why don't you make it the answer and I'll select it: engineeringtoolbox.com/wire-gauges-d_419.html $\endgroup$
    – leeand00
    Commented Apr 14, 2016 at 19:33

The block on the supply will accept the bare wire

enter image description here

you could use the yellow in the middle on the right, but the screw on the block essentially does its own crimp.


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