Guide: Install PSU and Switch

Overview

The Odin One MK1 design includes the addition of a power switch for the machine’s primary power source. The switch was added to the design to allow users to fully power off the machine (including all accessories) and was added at the request of users.

The switch in this case allows or disallows the flow of current to the PSU from the grid power source. There is a common misconception when dealing with switches and the difference between AC and DC power sources.

In this guide we will discuss this important but common misconception as well as describe the correct method of installing and wiring the power switch.

Note: This guide only discusses the process of wiring and does not cover the installation of the 3d printed PSU cover which can be found in the parts directory of the main repository for the Odin One.

AC vs DC Switching

There is a misconception that exists between the use of AC rated switches in DC circuits. The understanding is that if a switch has a rating of 20 amps @125V AC it should have no problem handling 10amps @12V DC. In reality this is not the case, current capacities drop significantly between AC and DC circuits—in other words, current is not current regardless of circuit.

There are a few elements at play here, however, an important concept to consider here is that AC current has a ‘zero current’ twice every cycle. That means that an AC source on a 60 cycle circuit will have a current of zero 120 times per cycle. This equates to a significant reduction in demand placed on a switch.

With that in mind, we can estimate that the amp rating of an AC switch is diminished by ~1/60 (depending) when used on a DC circuit. So, if we consider the 125V AC circuit on the Odin One, its current capacity (amps) is around .3amps (when used on DC circuit) — not nearly enough to handle the 10amp DC output of the PSU @12V.

The critical takeaway here is that the AC switch for the Odin must be used to disrupt power from the AC source and not the DC output of the PSU. In addition to the capacity issues of the switch, using the switch on the DC output still allows power to run to the PSU and then to the switch — this is something that provides no benefit but could pose significant negative results if certain scenarios occur.

The Switch

The Odin One uses a 20A 125V AC (15A 250V AC) six pole switch. This switch is well suited to handle both US/EU power sources and its capacity is within the safe operating capacities of standard grid power sources.
The six pole switch is designed to allow for 2 separate power supply inputs with one shared output, however, the Odin only uses one.

The switch’s markings are 1a, 1, 1b and 2a, 2, 2b—these are described below.

• 1: Represents +Pos
• 2: Represents -Neg
• A: Represents: Power input a
• B: Represents: Power input b

So… 1a is the terminal for the +Pos input of the a power supply and 2b is the terminal for its negative. In our case, these are the +Pos and -Neg wires from the ground fault cable (cable that plugs into the wall).

The 1 and 2 without an a/b designation are the output terminals, these are what go to the PSU.

Wiring the Switch

Warning: Do not plug in the wall plug until you have completed the wiring process and closed the PSU.

Warning: This guide is specific to the switches used by us, if you are using a different switch refer to that switches documentation.

Warning: Use common sense when dealing with electricity. If you are unsure ASK!— if you don’t feel comfortable doing this find someone who is or conduct the appropriate research. Nothing we are discussing here today is worth risking your safety or property.

In wiring the switch we are connecting 4 critical elements together:

1. Wall Plug
2. Switch
3. PSU
4. Printer

This provides the power source, AC to DC conversion, and control (ON/OFF) of the power flow.

You will need the following:

• Ground Fault Cable (the kind used for desktop computers)
• Power Switch
• PSU
• Odin One 3d Printer
• Terminals (16 gauge)
• Some Wire
• Basic Tools

Step 1:

You will start by stripping back the ground fault cable exposing its wires.

After doing this strip back the wire exposing a bit of the copper.

Using a crimper, crimp a terminal to the Positive and Ground wires leaving the Neutral wire exposed.

Note: In this case, our wire coding is as follows

Black: Pos Green: Ground White: Neutral

If you are unsure of this, or your wires differ find someone who knows or research this on the Internet.

Step 2:

Cut two lengths of wire, each approximately 4 inches in length. To maintain coding you may choose to use green and black wire for this.

Strip the ends of the wires back exposing some copper. Crimp a terminal to one end of each of the wires you just cut.

Step 3:

Plug the free wires into the 1, 2 terminals of the switch.

Using the screws on the PSU, fasten the green wire to the ground input of the PSU (identified with ground symbol). Now do the same for the black wire attaching it to the ‘Live’ input on the power supply (identified with an L).

Step 4:

Next, plug the terminals on the ground fault cable into the switch’s 1a and 2a terminals where 1a represents +Pos (black) and 2a represents -Neg (green).

Fasten the neutral wire to the PSU’s neutral input terminal (identified with an L).

Step 5:

Next, you will cut 2 additional wires to a length you see fit. These wires will connect the printer to the PSU.

Strip both ends of each wire exposing the copper.

Fasten your +Pos wire to an available ‘+Pos’ output on the PSU.

Fasten your -Neg wire to an available ‘-Neg’ output on the PSU.

Finally, fasten these wires to the main power in on your control board taking note of the silkscreened labels for positive and negative.

Clean-up

Prior to applying power to the machine, be sure to verify (double/triple check) your wires. Make sure no wires are touching and the PSU is fully enclosed and free of obstruction or debris.