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Revision to Choosing the power supply

Kevin Delaney

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-[summary]The two main decisions to make when choosing a power supply are the voltage and total power required. In general 24V is recommended and a power supply that is rated for at least 20% more than is required provides some headroom.[/summary]
+[summary]The two main decisions to make when choosing a power supply are the voltage and total power required. In general, 24V is recommended and a power supply that is rated for at least 20% more than is required provides some headroom.[/summary]
== Voltage ==
-The Duet WiFi and Duet Ethernet work with a VIN supply of between 11V and 25V. Usually, 12V or 24V is used because other components (heaters, fans etc.) are readily available in these voltages. There are three factors that may make 24V preferably to 12V:
+The Duet WiFi and Duet Ethernet work with a VIN supply of between 11V and 25V. Usually, 12V or 24V is used because other components (heaters, fans etc.) are readily available at these voltages. There are three factors that may make 24V preferable to 12V:
-* A 24V bed heater takes half the current of a 12V heater of the same power. So you can go to double the heating power before you need to use an SSR to control the bed heater. This means that 24V is generally advisable for printers with a bed larger than about 200mm square, unless you use an AC mains voltage bed heater. See [[Choosing a bed heater]].
+* A 24V bed heater takes half the current of a 12V heater of the same power. So you can go to double the heating power before you need to use an SSR to control the bed heater. This means that 24V is generally advisable for printers with a bed larger than about 200mm square unless you use an AC mains voltage bed heater. See [[Choosing a bed heater]].
* You may need to use 24V to achieve the travel speed you want without losing too much torque. See [[Choosing stepper motors]].
-* If you intend to use the resume-after-power-fail facility, a 24V supply will be able to power your stepper motors for longer before the voltage fall too much. This makes it more likely that it will be able to complete the power fail script.
+* If you intend to use the resume-after-power-fail facility, a 24V supply will be able to power your stepper motors for longer before the voltage falls too much. This makes it more likely that it will be able to complete the power fail script.
== Total power needed ==
* Extruder heater power: Use the power rating of your heater cartridges. If you will have dual extrusion, allow for heating both up together. If you will be turning up the power supply voltage to improve bed heating power, remember that this increases extruder heater power too.
* Stepper motors: at full rated current, the power needed for each motor is its rated current times its rated voltage (if no rated voltage is specified, use the square of the rated current times the phase resistance). This is the power at standstill. To allow for driver losses and the extra power needed to create acceleration, add 50%. Multiply by the number of stepper motors.
-* Fans: 3W per fan is a generous allowance for small axial fans. For blower fans, work out the power requirement from the data sheet. Note the fan outputs are rated to 1.5A maximum.
+* Fans: 3W per fan is a generous allowance for small axial fans. For blower fans, work out the power requirement from the datasheet. Note the fan outputs are rated to 1.5A maximum.
* PanelDue: with a 7" screen attached it draws about 3.5W.
* Duet: allow 2W.
These are similar to the MeanWell supplies but are made to lower quality standards. They are available very cheaply from eBay suppliers. They usually claim to be CE-compliant, but take this with a pinch of salt because some of them use leaded solder. They include voltage adjustment potentiometers.
-Expect these to be less reliable than MeanWell and similar quality PSUs. On the other hand they may also give years of service, and if they do fail they are cheap to replace. If you choose one of these then it is recommended that you get one with at least 20% more power capacity than you expect to need.
+Expect these to be less reliable than MeanWell and similar quality PSUs. On the other hand, they may also give years of service, and if they do fail they are cheap to replace. If you choose one of these then it is recommended that you get one with at least 20% more power capacity than you expect to need.
=== ATX power supply ===
* The fans in the power supply can be quite noisy. The other types of power supply may be available in fanless versions, depending on the power rating you need.
-The power rating of an ATX supply is based on a combined load on the 12V, 5V and 3.3V outputs. So you need to ensure that the 12V output alone is capable of supplying the entire power requirement of your printer.
+The power rating of an ATX supply is based on a combined load on the 12V, 5V, and 3.3V outputs. So you need to ensure that the 12V output alone is capable of supplying the entire power requirement of your printer.

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