3D Printer Power
There are 4 main parts that relate to supplying power to your MendelMax printer:
- IEC Power Cable
- Power Switch with Fuse and Socket
- Wiring the Switch and Power Supply
- Power Supply
We’ll walk through the basics of each component in the sections below, but please, please, please consult an electrician if you’re not 100% comfortable with doing your own wiring. I am not an electrician. You are solely responsible if you burn down your own house (or burn/shock/electrocute anything or anyone else for that matter) by following anything you read on the Internet, so get help from a professional if you have any reservations about taking on this responsibility.
IEC Power Cable
The IEC Cable connects your wall outlet to the Power Switch. One end is a standard 3 prong connector, and the other is a C13 connector – in essence, the cable looks like this:
Power cables come in a variety of lengths and gauges. Length-wise, consider how far you plan to keep your printer from the nearest power outlet – and if you ever plan to move your printer or take it anywhere, a little extra length doesn’t hurt. I generally recommend 10′ power cords as being a good compromise between long enough and not overly long. YMMV. Gause-wise, you can generally find a wide range, everything from 14 gauge “server power cords” to 18 gauge power cords. 18 gauge is more than enough for the 2-4 amps (max) of 120V AC that your printer will draw from a wall outlet.
“IEC Power Cables” are so named because the International Electrotechnical Commission defines a vast range of international electrical standards, including those used for non-locking appliance connectors, such as the C13 coupler (pictured above), and the C14 coupler that it mates to.
Power Switch with Fuse and Socket
The power switch allows you to elegantly turn your printer on and off like any other electrical device. The “socket” is the C14 coupler that the power cord mates to. And the fuse is an optional component that can help protect from a dangerous short circuit. Sometimes these 3 components are separate, and sometimes they come in an all-in-one configuration, like the one pictured below:
Either individual components or an all-in-one component will work, but I find the all-in-one component easier to work with, and the built-in fuse holder is a definite plus.
Sizing the fuse is potentially a confusing endeavor. Most fuses receive a rating like this one: “5x20mm, 250V, 8 Amp, Quick Blow Fuse”. The “5x20mm” refers to the size – 5mm in diameter, and 20mm in length. This is the appropriate size for the all-in-one switch pictured above. “250V” specifies the maximum voltage rating. A 250V fuse will work just fine in a 120V (U.S. Home) environment as well as in a 240V (E.U. Home) environment. “8 Amp” refers to the maximum current that the fuse can conduct reliably before the fuse “blows” or disconnects the circuit. Different fuses have different ratings, and due to current draw spikes that often occur when powering up a device, a general rule of thumb is to choose a fuse that handles double the expected current draw. Thus for a printer that is expected to draw a maximum of 4 amps, an 8 amp fuse fits the rule of thumb. And there are three main types of fuses – “Quick Blow”, “Slow Blow”, and “Time Delay”. “Quick Blow” fuses typically will blow within 0.1 seconds when their rating is exceeded, such as during a current draw spike. A “Slow Blow” fuse typically requires the load to be exceeded for 10′s of seconds before it will blow, and a “Time Delay” fuse can last even longer. “Quick Blow” fuses are the type needed for a 3d Printer.
Wiring the Switch and Power Supply
Wiring as found in U.S. residential applications usually consists of a three-core wire consisting of green, black, and white wires. If you live in the U.S. and you’re never heard the saying “Green is Ground”, then you should absolutely stay away from doing any AC wiring yourself… This leaves the black (or brown) wire also known as the “Live” or “Hot” wire; and the white (or blue) wire – the “Neutral” wire.
Wiring the switch goes as follows for the all-in-one component pictured above (but please double check your specific device for your proper wiring):
Basically you’re just wiring the connections so that the circuit is completed when the power switch is in the “on” position.
- Green is ground, and that wire connects directly from the IEC terminal to your power supply, as part of the ~12″ long power cable.
- Blue (or white) is neutral, and it gets a short connection from the IEC terminal to one side of the switch, and then the other side of the switch is part of the ~12″ long power cable that goes to your power supply.
- Brown (or black) is your “hot” or “live” wire. Internal to the switch, the “live” connection from the IEC terminal gets routed through the fuse compartment. Once out the other side of the fuse, you use a short jumper to connect to one side of the switch, and then the other side of the switch is part of the ~12″ long power cable that goes to your power supply.
The power supply end of the wires is far easier, as most power supplies are marked with “ground” (standard ground symbol), “N” or neutral, and “L” or live/hot. Here are examples for both green/white/black wiring, and green/blue/brown wiring:
The next likely question is about what gauge wire to use. Since we’re still dealing with 120V AC, it is appropriate to just use a section of interior wall wiring that would normally be used to carry 120V AC.
Another common question is whether bare wire leads can be used. The answer is yes, but you’ll make your life easier by using proper terminal connectors. Female spade connectors can be used on the power switch (because the power switch contains all male spade connectors), and male fork connectors can be used on the power supply side. You should try to use insulated connectors if possible.
And finally, there is always a question about safety – you should make sure that none of this wiring is exposed, can be shorted, or poses any sort of risk to anyone near your printer. Where you connect the all-in-one power switch to your printer, there should be a sealed box that contains all of the wiring. The wires leading from that sealed box to your power supply should be shielded, and you should be careful that no stray strands of wire accidentally touch from one wire to another. Crimp terminals with a “fork” or “spade” can help with this, but overall, just be careful and consult an electrician if you’re not one.
And finally, there’s the power supply itself. If your printer is a 12V printer, using a 12V electronics package like RAMPS, you need a 12V power supply. The amp rating should be greater than the sum of your connected items. For example, a heated bed can take 11 amps at 12V. Stepper motors can take an amp or more each. The hot-end can take 2-3 amps. Any LCD panel, LED lighting, fans, etc… can all take additional current. So I generally recommend a 12V 30A power supply for 12V 3D printers. 24V is becoming a more common option on 3D printers, so as time goes on, you should at least consider thinking about looking into a 24V system. Here is a typical power supply:
This type of power supply typically has a translucent orange plastic bit that flips up and down to cover the electrical connections, but you should definitely consider printing a part on your new 3d printer to fully contain the wires.
And in closing, it’s worth mentioning again: consult an electrician if you are not one.