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Main Power Input

Without power, your board can not do much. The board uses power to operate the control logic and to move stepper motors, and power heating elements, fans, and others.

How to choose a power supply unit (PSU)

Two power supplies are required, 5.0V and ‘bulk’ power (VBB).

5.0V supply

VBB supply

General Notes

Multiple-output power supplies are available. In some cases, a minimum load must be applied to the primary output before the secondary output will be regulated to within tolerances. For example, a dual 5.0V and 12V supply might regulate the 5.0V well at no-load conditions, but the 12V output may be low until power is drawn from the 5.0V supply.

EMI Filtering

Electromagnetic Interference (EMI): Digital logic and power circuitry (such as stepper motor drivers) switches currents and voltages on and off very rapidly. This produces EMI proportional to the voltage, current and rate of switching. EMI can be radiated (as radio waves) and/or conducted through the power line cord or other connections. EMI can interfere with (produce noise in or prevent proper operation of) other equipment, including sensors and motion encoder modules. To reduce these effects, an EMI filter module may be added to help reduce the conducted emissions. An EMI filter module may not strictly be needed, however it is often simpler to take protective measures from the start rather than e.g. searching for the cause of strange, intermittent behavior or coming back to failed 3D prints for months – and then put in an EMI filter module.

Fuses / Circuit Breakers

A typical US AC wall outlet provides 110V to 120V and is protected by a fuse or circuit breaker with a 15A or 20A rating. As (for example) a motor load such as a refrigerator or saw briefly draws a much higher starting current, in order to avoid ‘nuisance trips’ a 20A rating does not instantly remove power when that load is exceeded.

A VBB power supply rated (for example) 12V at 10A can provide up to 12V x 10A = 120W (Watts) of DC power. Power supplies are not 100% efficient, thus it will require 5% to 30% more than 120W of input power to produce 120W of output power. It is usually safe to assume at least 70% efficiency at full load (higher for more modern supplies), so the power supply will only need perhaps 1.5A at 120VAC input. A 1A, 5V supply will require much less than 1A at 120VAC input.

While the equipment can only use perhaps 2.5A, the AC wall outlet will provide at least 15A to 20A continuously without tripping the circuit breaker or blowing the fuse. It would be possible (though rare) for a fault condition that drew for example 10A at 120V = 1200W to occur, which would be a fire hazard, without tripping the breaker. If you wish to address this possibility, adding an additional fuse and/or circuit breaker with (for example) a 3A rating in line with the AC ‘hot’ wire will ensure that if there is a lot of excess power being drawn due to a circuit failure, then this fuse will blow or circuit breaker trip, and power will be removed. Too low a fuse or circuit breaker rating will result in ‘nuisance’ trips.

Setup

Make sure you use a Regulated Power Supply, make sure you connect the ground wire for the mains to the power supply, and if it has a fan, make sure it has sufficient space around it to let air flow and cool it appropriately.

To wire the power supply unit to mains (wall AC power), make sure you connect the right colored wires to the right connectors on the PSU. The 3 connectors are “live”, “neutral” and “ground”. Color changes from cable to cable. You can find charts for your specific country/cable on the internet, but the following colors are the most common:

Standard Load/live color Neutral color Earth color
US Black White Green
Europe Brown Light blue Yellow/Green

Once the wires connected to the PSU, make sure none of your computers is doing something important (like a system upgrade). In case something goes wrong, plug the PSU into a power strip with an on/off button. Then turn that button ON. If your house loses power, you did something wrong. If an LED illuminates on the PSU, everything is fine: unplug the PSU and continue.

If you are new to wiring, please check our how to wire guide.

[!DANGER] NEVER manipulate mains (220/110V) power wires while they are plugged into the wall plug. Unpleasantness and/or death are common consequences of not respecting this rule.

[!DANGER] Ground your printer’s frame by connecting it to the Earth terminal on your power supply. In the (unlikely) event that a power supply wire comes undone and touches the printer’s frame, this will prevent you from getting an unpleasant and/or deadly shock.

Now that the PSU is getting mains power, your PSU is converting it into 12V or 24V DC (Direct Current) power. You need to connect wires from it to the Smoothieboard to provide power.

The most important thing for DC is to respect polarity: + goes to +, - goes to -. On the PSU, + terminals are indicated as +, V+, 12V+ or 24V+. Ground (-) terminals are indicated as -, V-, COM or GND.

On the Smoothieboard they are indicated simply as + and -.

Smoothieboard Power Connections

By convention, black (sometimes brown) wires are used for ground, and red (sometimes orange, white or yellow) wires are used for power connections.

You may want to turn on the power supplies and test the output voltages before connecting them to the Smoothieboard (and turn them back off before connecting).

Once the wires are correctly connected, you can turn the PSU ON. If everything was done correctly, the red LED (marked VBB) on the Smoothieboard will light up brightly.

[!WARNING] If the VBB LED does not light up, immediately turn the PSU off. Check polarity, and check all the connections are strong and properly done. When you turn the PSU on, make sure you are ready to immediately turn it back off.

Now that the board has power, you can use that power to move things!

Emergency stop

It is recommended you setup an emergency stop button on your machine, so that in case of a problem, you can easily and quickly turn the machine off. For information on how to do this, please read EmergencyStop.